Some numbers for sites...

I think I've already given numbers for this in the discussions above. For the record (and this may change with playtesting) a lousy square (desert, tundra...) might have one agricultural site, steppe might have a few, rainfall agriculture-type squares would probably range from 5 to 20, and vastly productive agricultural lands like ancient Egypt might have something like 50 sites per square along the Nile. Irrigated desert agriculture poses a bit of a problem, since unless the irrigation is there, the lands almost useless. So I think we might need a special case to handle such lands. But for demo 5 I think we can't ignore the distinction and see how the system works in general.

The rule of thumb is there should be as many sites as ancient agrictulture could support population over the area of the square. So if on average a square in China supported 30K people, then there should be 30 sites. The exception is lands where heavy investments in irrigation are required. There I would cut the pop number by 2/3 or so since the investments in irrigation will increase the yield above the usual amount just given the sites.

Ecology generation:

The first step is to generate climate zones. There are seven climate zones per hemisphere, determined mainly by latitude. Each tile is assigned a base climate based on latitude:

Tropical: equator-12
Sub-Tropical:12-24
Warm Temperate: 24-36
Cool Temperate: 36-48
Sub-Arctic: 48-60
Arctic: 60-72
Ice Cap: 72-pole

As an option, there could be a bit of randomness to these numbers at the start. It should also be possible for these to be changed in the game due to varying solar activity and/or human induced global temperature change.

These climate zones are modified by altitude and ocean currents. Every 111 meters above sea level is equivalent to a latitude of about 100 kilometers, or one tile, closer to the pole. After the climate has been adjusted for altitude, ocean current vectors are generated at random. These currents then influence the climate of nearby land regions. These areas are given the unadjusted climate of tiles a certain distance away in the direction that the current came from. This distance is determined by the size of the vector.

So a strong current moving north in the northern hemisphere could cause lot of the nearby continent to be changed from a sub-arctic to a cool temperate climate. This duplicates effects like the Gulf Stream's, which gives western Europe a warmer climate than its latitude would indicate.

The main effect of climate zones is to alter the number of farm sites, as warmer climates have a longer growing season:

Tropical: No Change
Sub-Tropical: -10%
Warm Temperate: -20%
Cool Temperate: -30%
Sub-Arctic: -50%
Arctic: -70%
Ice Cap: -100%

All site numbers are rounded to the nearest integer.

Climate will also determine what kinds of vegetation will grow in the tile, although in many cases this difference will only be cosmetic. Climate can have other uses, such as influencing the attrition of military units.

After the climate is generated, land values are assigned at random in fairly large patches. "Land Value" is a term that includes every geological and chemical influence on plant growth in that area. It ranges from zero, meaning nothing at all (not even lichen) can grow, to eight, which represents exceptionally good growing conditions.

Land values are limited by climate. Ice Cap terrain always has a land value of zero. Arctic terrain, which is ususally ice or permafrost, is limited to land values of zero to three. Sub-arctic terrain can only have land values from zero to five.

After the soil is generated, the water ratings of the terrain are assigned. There are two types of water: Natural and Potential. The Natural Water Rating, or NWR, describes all of the water that is naturally available to plants. The Potential Water Rating, or PWR, is the groundwater and/or streams and rivers that are not naturally available to plants but can be used by humans for various purposes.

NWR values go from one to eight. For the NWR generation, the tiles are assigned water ratings in large random patches. Then, wind vectors are generated at random. If a wind current goes from the sea to the land, the coastal tiles will have a higher NWR. If a wind current is blocked by high elevations, the downwind tiles will have a much lower NWR and the tiles on the windward side of the high elevation tiles will have a higher NWR. All of these ratings are then modified as follows:

All tiles in the Tropical climate zone are given a NWR of +2, all tiles in the Warm Temperate climate zone are given a NWR of -2, and all tiles in the Cool Temperate climate zone are given a NWR of +1. This is due to the large atmospheric convection cycles that would probably occur on any earthlike planet.

Rainfall, which is the main part of the natural water rating, reduces the soil rating due to leaching and erosion. The reduction is based on the terrain and amount of water:

------------Flat--Roll--Hill--Mtn.
NWR 4:--0-----0-----0----1
NWR 5:--0-----0-----1----2
NWR 6:--0-----1-----2----3
NWR 7:--1-----2-----3----4
NWR 8:--2-----3-----4----5

The soil rating is increased by natural river flooding, so provinces at the downstream end of large rivers will have their land value increased by one to three. Thus, the best farming terrain in the game is likely to be flatland near rivers with moderate amounts of rain. This will naturally have very good productivity, and it can be irrigated so that both values are at maximum.

All water and soil ratings are not allowed to be below zero or above eight. If they do, they are simply assigned ratings of the minimum or maximum value allowed.

After land values, water, and climate are assigned, the ecological provinces are created and filled with natural vegetation. Each vegetation type can grow only in certain conditions, but most tiles will be able to support multiple types of vegetation. An ecological province is any patch of land, generally five to thirty tiles, that has the same climate, soil, and water. An ecological province is assumed to be a region with almost identical environmental conditions. Each ecological province is assigned one vegetation type out of all the vegetation types it could support. All vegetation has climate, soil, and natural water requirements. This base vegetation of a province will not change naturally, although the borders of the provinces could shift.

After ecological provinces are created, each one is given a PWR at random. Then, this PWR is adjusted for rivers and rain. Rivers add one to three to the PWR. The NWR then adjusts the PWR:

0:-2
1,2:-1
3,4:0
5,6:+1
7,8:+2

Aquatic ecosystems like wetlands, lakes, and oceans are determined by a different system. Water is irrelevant, and the ecology is determined by climate and a single Water Quality factor that goes from zero to eight. This factor has nothing to do with how suitable the water is for humans to drink or use; it describes how well the water can support life.

Wetlands are generated on land tiles, and they can have different vegetation types like other terrain. There are three types: Basin, Riverine, and Coastal. They are generated after soil and water ratings are assigned; these numbers are stored even though they do not affect the wetland vegetation.

Basin wetlands form on flat or rolling terrain where the water table rises above the land. If the PWR is seven or eight and the NWR is greater than five, then an ecological province can become a wetland province. Riverine wetlands occur alongside rivers in flat terrain. They have a chance of occurring in any ecological province that a river is passing through. This chance is increased by a high PWR. Ecologically these wetlands are similar to Basin wetlands, and have the same vegetation types. Coastal wetlands and estuaries form on flat coastal areas, often at the mouths of rivers. Because of their high salt concentrations, they have a different set of vegetation.

Wetlands can increase disease, but they decrease the chances of flooding, decrease the effects of pollution, and restore potential water ratings of nearby provinces. All wetlands greatly slow the movement rate of units and are impassable to most mechanized units. Wetlands can be drained to make normal terrain, which is usually fairly good farmland. When this happens, the terrain is given its original stored Soil and Water ratings.

Lake and Ocean tiles also have ecology types based on Water Quality. The main effect of this will be fishing yields, but hopefully there will be undersea exploration and colonies later in the game. This will cause interactions with underwater terrain similar to the normal land interactions (movement, farm productivity, terrain improvements, etc.)

Farming and Fishing:

The number of farm sites per tile is based on the land value and natural water value of the ecological province the tile is in. The base number of farm sites is the adjusted land value times the adjusted water value. This site number is then adjusted by climate. The maximum value for either rating is eight, so the best land in the warm temperate zone has 8*8*.8 = 51 sites. Note that this kind of productivity can only be achieved be irrigating a province with land value of eight, as a high NWR lowers the land value.

The land value can be adjusted by many things, and the water value can be adjusted by irrigation. The water value can be adjusted upward to either eight or the NWR plus the PWR, whichever is smaller. So if a province's NWR was 4 and the PWR was 2, irrigation could produce an adjusted water rating of 6. But if the NWR was 6 and the PWR was 4, irrigation could only produce an adjusted water value of 8, which is assumed to be all of the water that any crop would need.

All farming calculations and changes must be managed by economic/political provinces, but their effects will depend on the ecological provinces the tiles are in. Thus it will be more efficient for the civ if ecomomic provinces are at least roughly correlated to ecological provinces. The base land and water nalues will depend on the ecological provinces, while the adjustments will depend on the economic/political provinces. The economy model will therefore need to store the province's soil and water adjustments in the characteristics it defines for each province.

Extensive farming can lower the land value of the terrain. Any large increase in the quantity of farming triggers a check for decrease in the land value. If the check fails, then the farming is assumed to be sustainable. If it passes, the province's soil value slowly decreases. This will have the effect of lowering the farm sites number. Technology advancements can prevent this, but often at the cost of pollution.

Fishing has an impact of the ocean. To determine if an area is being overfished, a check similar to the land change check would be done on aquatic provinces. If the province passes the Overfishing check, the Water Quality rating of that area decreases at some rate. If the same rate of fishing is maintained, the decrease will accelerate until the fishery collapses. If fishing is stopped for a period of time, then the water quality can increase again as the ecosystem is restored to initial levels. This change in Water Quality would not affect undersea farms or the base province value. It would only be a temporary adjustment for fishing purposes.

Potential Water Rating:

This is a new addition to the model, but I think it is important. Wars have been fought over water rights, and groundwater depletion is a big threat to our future well-bring. My treatment is obviously a first draft, and will have to be revised somewhat after I get input about it.

In addition to determining the ability to irrigate crops, the PWR should determine how much water is available to the people in a province. Each population point in a province needs a certain amount of water, and certain industries have water requirements. All of this water use is added to the irrigation amount to get the total province water use.

The amount of water available to the province is based on the total PWR of the province's tiles. Rainfall is rarely used directly; streams, rivers, and groundwater are our primary ways of geting water. As water is used, the PWR can decrease. Tests for this decrease should be run pretty frequently. The test depends on water use, the NWR, the presence of nearby wetlands and rivers, and the civ's technology.

If the PWR does decrease, the province must conserve water or get water from somewhere else. Aqueducts or pipe networks can be built to send water in from neighboring provinces. If it is not possible to get water from within your civ, you might have to buy or take it from a neighbor.

High technology and capital investment can help provide water from desalination plants or water recycling plants. The PWR for the province is increased if these are built.

Other Human Induced changes:

Human activity will influence the terrain. At low levels of habitation and use, the province simply keeps its natural state. But at higher population levels or intensive use of the tile, changes could occur.

Deforestation is the simplest human-induced change. Whenever there is a significant change in human activity on a forest province, a deforestation check is run. If the terrain fails the deforestation check, the forest use is assumed to be sustainable and the terrain is not checked until there is another big change in land use. If the deforestation check is passed, then the province will change vegetation after a certain number of turns. The deforestation check depends on the level of land use, the technology levels of your civ, the type of forest, and a random number representing the forest’s ability to renew itself.

Deforestation will often result in a lot of soil loss due to erosion. Deforestation would result in land value losses of zero or one on flat terrain, zero to two on rolling terrain, one to two on hilly terrain, and one to three on mountainous terrain. This soil loss would be a permanent change for the province. Also, the province would be assigned a lower change number for border changes, so the surrounding provinces would be more likely to move in to replace the former forest province.

Pollution from industry, mines, and farms can also impact terrain. The check for this change would be similar to the logging and soil loss checks. There are several types of pollution:

Acid Rain occurs downwind of large industrial centers that produce atmospheric pollution. It is most likely to happen when there is a high natural water value, especially when a wind vector crosses a mountain. If the check is passed, the province's Land or Water Quality rating decreases at some rate that is based on the severity of the pollution. This decrease changes the maximum value, so it is not possible to fix acid rain with fertilizers. After the pollution stops, the maximum Soil or Nutrients value slowly increases to what it once was.

Solid pollution of all types has the same effect as acid rain, but the effect is more severe and is localized to the province the pollution originated in.

Liquid pollution has the same effects as solid pollution, but it also can travel downstream and affect any wetlands provinces below the source of the pollutants. Cities downstream would also have the problems associated with the pollution. If a polluted river crossed the border between two civs, this could have diplomatic consequences. The same is true of acid rain and air pollution.

Human activity can have more subtle effects on the land. Some types of land use, like extensive grazing, can cause an entire ecological province to change form. This check would combine the border change and logging checks.

Warfare can also change the land. Any drawn-out modern conflict has a chance of permanently scarring the land due to shells, chemicals, etc. Nuclear weapons would reduce the Land value to zero for some time period.

If the player wanted to do reclaim land from the sea, there would have to be a check for the chance of success and the upkeep the land requires. If the land was generated, it would be assigned Soil and Water values. There would always be the chance of the land flooding again if the dikes were not properly maintained (or if they were bombed by a clever enemy). All of the contiguous land reclaimed this way would form a single ecological province.

Widespread construction in a province has a chance of reducing that province's soil value by the same amounts as deforestation.

Defoliation or other improper use of hilly or mountainous terain would cause a province to be checked for landslides. If landslides do occur, the towns and terrain improvements are all damaged or destroyed. Also, the soil rating of the tile would decrease by one or two.

This and other soil loss will affect water quality. Whenever soil loss occurs for any reason other than farming and border changes, any bodies of water in or adjacent to the province will have their Water Quality temporarily reduced by that same amount. So if deforestation reduced the soil of a province by one, and then a landslide reduced the soil value by two, the Water Quality rating of a river running through that province would be temporarily reduced by three.

Natural changes:

After the terrain is generated at the start of the game, it can undergo changes as time progresses. Some of these will be small and mild, but others will have a big impact on almost everyone.

Checks are performed at random for natural changes. If the check passes, the change occurs after a certain number of turns. Between the time the check passes and the change happens, a civ with the proper tech levels may be notified of the impending change. A civ with good enough technology could work to prevent the change.

The simplest and most common change is a shift in the border between two ecological provinces. This would usually result in a few tiles switching vegetation. Checks for this would be performed on one border of about fifty ecological provinces every turn. If the check is positive, the border shifts. The check depends on the similarity of the Land and Water values of the provinces; the borders of two provinces with similar geological characteristics are much more likely to shift then the borders of two dissimilar provinces. Also, the vegetation of the two provinces affects the chance of the shift.

If an ecological province grows too big, it is split into two different provinces. Each province remains unchanged, but they are tracked seperately.

So a strong current moving north in the northern hemisphere could cause lot of the nearby continent to be changed from a sub-arctic to a cool temperate climate. This duplicates effects like the Gulf Stream's, which gives western Europe a warmer climate than its latitude would indicate.
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Note that there are both warm and cool currents so both should be incorperated.

The main effect of climate zones is to alter the number of farm sites, as warmer climates have a longer growing season:

Tropical: No Change
Sub-Tropical: -10%
Warm Temperate: -20%
Cool Temperate: -30%
Sub-Arctic: -50%
Arctic: -70%
Ice Cap: -100%

All site numbers are rounded to the nearest integer.
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Rich, you should be careful on this. Many cooler climates during the short farming season are capable of producing more during that period than other places warmer year round. These places are nearer to the poles where during the summer sunlight can be constant, in some cases 24 hours. This offsets the shorter time period greatly as for example Alaska is known to hold the record on size of many of the crops produced, yet it really doesn't have any major current to carry warm water to it.

All tiles in the Tropical climate zone are given a NWR of +2, all tiles in the Warm Temperate climate zone are given a NWR of -2, and all tiles in the Cool Temperate climate zone are given a NWR of +1. This is due to the large atmospheric convection cycles that would probably occur on any earthlike planet.
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So does that mean that even in a desert climate in the tropics, the minimum rationg is 2?

Also tiles around sub-artic and artic areas should get negative modifiers to this. Since NWR seems to represent mostly rainfall and dew and water vapor, in those zones there is little. FE Antartica is in addtion to being classified as an artic area is also classified as a desert because it recieves almost no rainfall at all each year (rain being in any form).

The soil rating is increased by natural river flooding, so provinces at the downstream end of large rivers will have their land value increased by one to three. Thus, the best farming terrain in the game is likely to be flatland near rivers with moderate amounts of rain. This will naturally have very good productivity, and it can be irrigated so that both values are at maximum.
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So basically in floodplains and on the delta area huh?

After land values, water, and climate are assigned, the ecological provinces are created and filled with natural vegetation. Each vegetation type can grow only in certain conditions, but most tiles will be able to support multiple types of vegetation. An ecological province is any patch of land, generally five to thirty tiles, that has the same climate, soil, and water. An ecological province is assumed to be a region with almost identical environmental conditions. Each ecological province is assigned one vegetation type out of all the vegetation types it could support. All vegetation has climate, soil, and natural water requirements. This base vegetation of a province will not change naturally, although the borders of the provinces could shift.
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Is 5 the mimimum throughout the entire game or just at the start? I'm asking because of things like deforestation in small, but concentrated areas or the creation of other factors which could reduce the size of one to another. I don't think it should be the case that 5 is the minimum, atleast after starting.

Lake and Ocean tiles also have ecology types based on Water Quality. The main effect of this will be fishing yields, but hopefully there will be undersea exploration and colonies later in the game. This will cause interactions with underwater terrain similar to the normal land interactions (movement, farm productivity, terrain improvements, etc.)
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I propose that lakes and oceans each have hidden farming sites that the player can only use if he has access to the right technologies. Farming on oceans might be harder, but can be done. Farming on lakes has been done and was done by ancient cultures so it should be allowed (although the right social, technological and other conditions must be met). Farm sites, atleast on lakes, would not be based on land value, but only water value as they would be on the surface of the water.

The amount of water available to the province is based on the total PWR of the province's tiles. Rainfall is rarely used directly; streams, rivers, and groundwater are our primary ways of geting water. As water is used, the PWR can decrease. Tests for this decrease should be run pretty frequently. The test depends on water use, the NWR, the presence of nearby wetlands and rivers, and the civ's technology.

If the PWR does decrease, the province must conserve water or get water from somewhere else. Aqueducts or pipe networks can be built to send water in from neighboring provinces. If it is not possible to get water from within your civ, you might have to buy or take it from a neighbor.
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Does PWR represent all the water because poluted water isn't really usuable water. Espically radioactive water.

Deforestation will often result in a lot of soil loss due to erosion. Deforestation would result in land value losses of zero or one on flat terrain, zero to two on rolling terrain, one to two on hilly terrain, and one to three on mountainous terrain. This soil loss would be a permanent change for the province. Also, the province would be assigned a lower change number for border changes, so the surrounding provinces would be more likely to move in to replace the former forest province.
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I still think "peremennt" isn't right Clash does take in the time scale for soil to repair ifself somewhat. I would say a period of 1000 years could repair a rating of 1 for soil loss in most areas. In artic areas, say 3000 years (still within clash timeline) and mountains can vary (1000-3000).

Pollution from industry, mines, and farms can also impact terrain. The check for this change would be similar to the logging and soil loss checks. There are several types of pollution:
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One type of pollution you didn't meantion was nuclear radioactive pollution. Either from man-made sources (most common) or natural sources (yes for those who didn't know there are cases of natural nuclear radition). The effects are differnt from others in that they are spread over larget area, getting weaker as they progress outward. Certain rocks can block radition though. Also radioactive soil can be carried downsteam. This type of pollution will last for thousands of years depending upon the amount of radiation, but will slowly be reduced.

Warfare can also change the land. Any drawn-out modern conflict has a chance of permanently scarring the land due to shells, chemicals, etc. Nuclear weapons would reduce the Land value to zero for some time period.
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Actually, that's right and yet wrong at the same time. FE the test sites for the H-Bomb are still unihabitable. You can walk around fine for a while atleast. Don't eat any plants though (and yes plants are thriving). The plants are all radioactive and would kill you.

If the player wanted to do reclaim land from the sea, there would have to be a check for the chance of success and the upkeep the land requires. If the land was generated, it would be assigned Soil and Water values. There would always be the chance of the land flooding again if the dikes were not properly maintained (or if they were bombed by a clever enemy). All of the contiguous land reclaimed this way would form a single ecological province.
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Hmmm. I wonder. What about future technologies being able to permantly reclaim land from the sea, although over a descent time period.

There is no need to have warm and cool currents. The curents have an effect based on the origin of the vector. A warm current is one that goes from a lower latitude to a higher one, and a cool current is one that does he reverse. Sorry that wasn't clearer.

I'll have to research the climate change in farm sites. I am fairly certain that the total amount of stuff you can grow increases at lower latitudes.

There are no really dry places between the latitudes of zero and 12. The entire climate band has extra rainfall because of the way air circulates. That is why I made the adjustment.

You are right; I may have to add adjustments for the arctic areas.

We should try to keep the province size above five for computational purposes, but it isn't an absolute minimum. You can get smaller.

I will have to think more about lake and ocean farming and come up with a more detailed way of assignimg sites.

Pollution should reduce PWR; that is a good point.

The province with eroded soil should shrink and disappear. The individual tiles will get an increased soil rating, even though the province does not.

I will have to consider radiation. It is different than other types of pollution and will probably have to be treated differently.

The model in general looks really good! I have some reservations that its trying to do to many things, but I think we will only be able to assess how far as the proper amount to go when we see what speed the final thing runs at, and get some feedback from playtesting. Right now I'm focused on how to do the handshaking between the ecological and economic models. So most of my comments will be in that area.

So as I understand it, when the player (or AI) does something like drain a swamp, the square that is modified either becomes part of a nearby relevant ecological province, or starts a new province. If I have it right, then that seems like a practical way to do it. I assume that expressly clearing forest for creating new farmland also falls under this heading. I realize that you have deforestation above, but that seems to be more on the level of incidental deforestation, rather than intentional. I guess I would like to see a few more details on how you would like to see changes like this work. I think that on the square basis we could have the changes be fairly abrupt, like the ones you envision when the boundary of an ecological province shifts. I don't think that would be too bad, seeing as the game is really designed more at the province level, and changing even a single square in a large discontinuous manner shouldn't have a huge effect at the provincial level.

What I need for the economic system is just a way to figure the cost and value of these transformations. So, for example, before the heavy plow there is really not that much incentive for Europeans to cut down their indigenous forest, because farming much of the land is very difficult anyway because of the heavy clay soils. (I can't remember if you were handling heavy vs. light soil types or not, I thought I saw this somewhere in the model) So anyway, in terms of our vegetation types (specifically farm site, and resource site, values), we need to determine some sort of hierarchy for the transformations people can intentionally do. I'll then try and figure out a cost for those transformations, and the Econ system will use those cost/benefit numbers to calculate if the improvements are worth doing. If you do have the soil types in there, then as soon as the heavy plow comes along, there would be huge economic effects as the people start clearing forest to make more farmland. I think whether we want to actually put this sort of detail in the game is debatable at this point, since some players will want it, and others would hate it ("What do you Mean clearing the land does no good!?") .

Irrigation:

I have done research on the effects of temperature on net primary productivity and found that my treatment of the effect of climate on farm site numbers is reasonable.

Atmospheric air circulation: The sun heats the air at the equator and in the tropics. The hot air masses then rise, and as the air rises the moisture is forced out of it. This moisture then falls as rain, and the result is that all of the tropical areas have high annual rainfall. These masses of hot dry air fall back to the Earth around 30 degrees latitude. As they fall, they soak up moisture, making the warm temperate climate zones dry areas. The result of this is that tropical climate zones will have a lot of rain and warm temperate zones will have less rain. The NWR rating adjustment reflects this.

Similar circulation patterns with smaller effects take place at higher latitudes. The Sub-Arctic zones have more rain and the arctic zones have less. My redefinition of climate zone latitudes caused a change in the settings; I should have caught this. The NWR adjustments are now:

Tropical: +2
Sub-Tropical: 0
Warm Temperate: -2
Cool Temperate: 0
Sub-Arctic: +1
Arctic: -1
Ice Cap: 0

I will have to experiment with the ecomomic spreadsheet before coming up with a system for dealing with lake and ocean farm sites.

Radiation Treatment Idea:

We define eight radiation levels. Each level represents twice as much radiation or fallout as the previous level. The radiation levels have the following effects:

Causes disease proportional to two to the power of the radiation level.

Reduces the Land and PWR values by the radiation level. This may cause the vegetation to disappear if the new land values are lower than the vegetation requirements. The vegetation is replaced with new vegetation that can survive in the lower land values. If the land value goes to zero, the square becomes a radioactive wasteland where nothing can grow.

An irradiated tile would be assigned a radiation number, and that number would decrease slowly over time. As the radiation number decreases, vegetation can be restored to its original state.

As far as I know, we are not going to track the kind of crops that are growing in the province. I assumed that additional water would enable people to grow different and more productive crops; it is not like you are adding more water to one kind of crop. People are assumed to switch crops based on water availability.

I was going to write a big, comprehensivve post replying to all of your last post, but I haven't yet been able to complete the parts that need the econ spreadsheet, so I'll just put some of it here:

Swamps are defined as ecological provinces like all other vegetation types. I thought we wanted to avoid single-square changes, so I had planned on altering the entire province at once. The player would order the swamp province to be cleared and it would be replaced with the new province. That system was designed before I realized how big a single province is. Altering the entire province would be a huge change, and the player might want to make smaller changes. Also, you seem to want to avoid abrupt changes at the province level. If you want to allow square by square changes, I could think of a way to do them. Or, the province could be partially cleared, resulting in terrain that was X% swamp and Y% drained, with Y increasing slowly over time.

Forest clearing would work the same way as swamp clearing. Again, I was thinking of changing the whole province or shifting the border, but square by square changes are possible if you think they should be included or we could do percent forest cover for the province.

The cost of transforming a province or square would have to be defined in the ecology model. There are two costs for clearing: The actual cost of the operation and the opportunity costs of the lost ecosystem. The operation cost is easy to define: The vegetation characteristics could include such a number. The opportunity costs, however, are more interesting and complicated.

Some oppportunity costs can be easily defined. If you destroy a forest you lose the ability to get wood from that square or province. The loss of one type of economic activity is the tangible opportunity cost of altering the terrain. However, there are also non-economic, intangible opportunity costs of destroying natural environments.

We have only recently learned the value of certain natural ecosystems. Wetlands provide a lot of benefits such as water purification and flood control that people didn't know about a hundred years ago. Thus, the percieved opportunity cost of destroying wetlands has risen. This is why the government no longer supports wetland drainage like it used to.

So, in Clash terms, the tech level determines the percieved intangible opportunity cost (PIOC) of destroying the natural terrain. A civ with a low tech level would see zero opportunity cost for draining a big smelly swamp, while a more advanced civ would see a very big opportunity cost in destroying a wetland ecosystem. And to further complicate things, the culture and social conditions of the civ will also impact this percieved opportunity cost.

Regardless of what the civ knows about, there will be a real opportunity cost to terrain alterations, in the form of flooding, erosion, loss of groundwater, etc. These changes will affect the civ over time, as the ecology model calculates the consequences of human actions.

It is impossible to predict exactly what will happen; the ecology model is a chaotic dynamical system with a lot of randomness. We will have to define an average real intangible opportunity cost for destroying natural ecosystem based on what will most likely happen. This will mean putting a cash value on things that are not economic, but we should be able to do it.

To further complicate things, the real opportunity cost of destroying an ecosystem will change based on how many tiles of that ecosystem are on the map. The marginal opportunity cost of losing a terrain type will increase as that terrain becomes less common.

So the PIOC is based on technology, society, and the average marginal real intangible oportunity cost (AMRIOC) of altering the terrain. The exact calculations for AMRIOC and PIOC are a problem best dealt with later.

The cost of the terrain alteration that is entered into the economic calculations is the operation cost plus the tangible opportunity cost plus the PIOC.

The benefits of terrain alteration are also divided into tangible and intangible benefits. The main tangible benefit is an increased number of farm sites. This can easily defined, and the economy model can put a cash value on the farm sites.

There can also be some intangible benefits to altering the terrain. Swamps do breed mosquitoes, and clearing them can reduce disease. These intangible benefits would be calculated in much the same way as the intangible costs of terrain alteration. A civ that did not know how malaria spreads would see little intangible benefit in draining swamps, while the perciened intangible benefit (PIB) of swamp draining would be much higher for a civ that knew about the role of mosquitoes in spreading disease. In some cases, the PIB alone could cause people to alter the terrain.

It may seem like these PIOC and PIB calculations would take a lot of time, but they will not be run for every square. There will be a few dozen terrain types, and all of the intangibles will be the same for every tile of that terrain. Unlike the tangible costs and benefits, they do not depend on the Land and Water values of the terrain. These PIOCs and PIBs only have to be calculated once for the entire civilization and then stored as variables to be accessed when the economic cost/benefit calculations are run. If time is still a problem, they do not have to be recalculated every turn. Some fraction of the intangibles calculations could be run every turn, so the variables for each terrain could be updated every four turns rather than every turn.

I will also give the progress report on the model:

Version three of the Ecology model is taking a while. The following issues to be worked out:

Disaster Model Cooperation

Month Based ecology model that includes seasonal variations (required because the game turns will last less than a year)

Lake and ocean farming

Increased farm sites with tech level

Swamp/Forest clearing system

Revised Water and Land calculations

Also, I am switching to an object oriented model, which is taking some more time to work out. This is especially true because I am in the middle of learning OO design techniques.

When I finally finish Version 3, I will tag certain routines to show what detail level they will be in. For example, the PIOC and PIB calculations detailed above would only be in detail level 4, while the deforestation system would be in levels 2 and above. (Even if you don't care about the model, you shouldn't be able to log the same stand of trees for 6,000 years.)

0: No ecology modeling. Ideal for battle scenarios.

1: Like Civ 2. Economic inputs depend on terrain. The terrain never changes naturally, but you can alter it. Ideal for slow computers or low bandwith multiplayer.

2: A "bare bones" version of the current model. A few of the processes are used to make the terrain change in simple ways. Ideal for those who don't care about the model.

3: A simplified version of what I am working on. This will probably end up being the default for a normal game.

So, we should probably try to define the ranges of some important animals. Hunted animals and domesticated animals kept for food are not very important because those will be handled in an absrtact manner, but draft animals and animals used in war should probably be tracked. These include oxen, donkeys and mules, horses, camels, and elephants.

If a civilization has no access to good draft animals, they will probably not be able to develop intensive agriculture. They will probably turn to hunting and a nomadic lifestyle if there are good hunting grounds, and if they cannot hunt they probably won't advance much, as the agriculture requires so much manual labor that there won't be people available for other things.

We probably can't handle draft animals as an abstraction because technology determines what animals can be used. They had to invent a special collar before horses could be used to plow fields. After they used that collar, they could use horses, which were faster than oxen and plowed fields more effectively. So this means we probably should define the availability of horses, oxen, and mules seperately.

I think that war animals need to be tracked. The availability of horses and camels are definitely important to the way a civilization develops, and if we want to include elephants, their range should be defined as well. I personally don't think we need elephants, because they actually had very minor impact on ancient war. They were not effective and they were not used much.

Do you think we should include dogs and cats? Dogs were important draft animals for the eskimos and they help with farming and other things, but I don't know if this is enough of an impact to justify including them. Cats definitely have an impact on rodent populations and food loss, but again I don't know if this makes them important enought to include. Let me know what you think.

I could define the natural availability of animals by ecological province. Each province would have the following animal related data:
Domesticatable (is that a word?) animals.
Huntable animals.
Oxen
Donkeys
Horses
Camels
? Elephants, Dogs, Cats ?

My list of important tamable animals:
Horses
Camels
Mules
Elephants
Oxes

However, I don't think that these specials should still be on the map after they have been tamed and integrated into the economy. At that point, I believe they should be modeled as province infrastructure.
This may seem odd, but as far as I can tell the equations would be the same. FE the number of horses available would be an important part of the farming and transportation infrastructure, as their presence increases the ability to complete economic activity.

But I'm getting off topic. This should be discussed in the economic thread.

I could generate lots of specials like the wild horses. Once the proper tech is researched, the specials would disappear and become a part of the province infrastructure.

However, I still think that Huntable animals should be treated abstractly. There are just too many of them and they are too widespread to be included as unique specials, so they should still be charactistics of the ecological province. This attribute would be used as a food input in the economic models, as labor turns the game into food. The ecology model would then determine the depletion of the herd in a manner similar to the deforestation checks.

Other domesticatable animals are a bit of a quandary, however. Theoretically, they should be treated like horses; they would start as specials and then become infrastructure. But there are just too many of them. I don't think anyone wants a map littered with wild chicken and wild pig specials. Then there is the fact that most common farm animals were domesticated before 4000 BC, so it would be pointless to include their wild counterparts.

But it does need to be modeled somehow. Cultures with domestic food animals are much less likely to hunt, and their diet will be different. I think there should be some modeling of the amount of farm animals in the province. And it can't be strictly economical, as some areas of the world, like the Americas, don't have animals that can be domesticated as farm animals. I need some help with this one.

A very good aspect of the specials plan is that it makes it much easier to add things like elephants, dogs, and cats. All we have to do is create the special and a couple infrastructure rules. They would simply be another instance of an existing class, so we don't have to do anything special to include them.

By the way, I should be working on adding specials to the third version of the Ecology model. While it wouldn't cover geologic specials like iron, it is the best place to model things like grapes. Mark, could you give me a list of the specials that are associated with the ecology?

Most of the posted stuff is very out of date. FE F_Smith posted an excellent idea for treating crops like the rest of the vegetation and we should work that in. There is also a bunch of other stuff that has been discussed in the months since the last model came out. There are issues regarding rivers, disaster modeling, mapsquare modeling plans, and much more.

I have a feeling that the entire model will have to be rebuilt from the ground up (literally!). So you probably don't need to worry much about what is in my mythical version three. It is getting almost as dated as the current version.

So let's see if we have learned enough about communication to collectively build the revised model from scratch. Be original and don't feel like any of the existing stuff is set in stone. Consider my exiting stuff to be mere suggestions, with as much merit as your own. Nobody has really done an ecology model like this before, so we should be able to start without any preconcieved ideas of what should happen. Let's hear from everybody.

I hereby divest myself of all ownership of the Ecology Model! It now belongs to the entire team! Let the new ideas fly!

1. We should try doing ecology on a square-by-square basis first. I have to take responsibility for pushing Richard into the ecological provinces idea in the first place to keep a lid on clock cycles used .
But I think that if the default model takes too much time when run square-by-square, we can trim it down and still keep the flavor the same.

A lot of the problems Richard and I had in docking this model and econ go away if you do ecology on a square basis.

I suggest we stick to having the ecology model influence the map at start-up, very much like what's being proposed in the OO Mapsquare thread:
Define climate zones
Implement NWR and PWR
Let the climate zones and water values affect output of individual squares

I think we should stick to a few terrain types (in said thread I suggested Deep Sea, Shallow Sea, Flatlands, Hills, Mountains, but your guess is as good as mine) and a few vegetation types (barren, grass, forrest, farmland, human habitation, same applies here). This gives 2 types of ocean squares and 15 types of land squares. Maybe even this is too many.

This way we could get a gametesting shot at some of the relations between the ecology model and the economical model

Next step (demo5.000001 )would be to implement rudimentary ocean current and wind systems, just to see how it works.

Previously I assumed that ocean had to be a separate terain type, but thinking a little more about this, I realise that this completely ignores the state of the ground beneath the ocean. I think instead it should be something like this:

There are two different base terrains, with a number of different variations:
Landlike: Flat, hills, foothills, mountains
Oceanic floor: Flat, ridge, trench
The transition zone betwen the two is shown by a cliff (either at the squareedge or inside the square). This consitutes a separate terrain type.
Water is handled like any other ground cover: In theory all of the above can be either above ocean level, partially above ocean level, or below sea level.
Each square should then have a base altitude, sqAlt, above some arbitrary zero level. Each terrain (flat hills etc) should have a base average height, teHeight, above the sqAlt. The planet object should have a ocean level value relative to the zero level.
If oceanic level < sqAlt then the square is above water level, water ground cover = 0%
If sqAlt < oceanic level< sqAlt + teHeight then the square is partially covered with water, 0% < water ground cover < 100%
If sqAlt + teHeight < oceanic level then the square is below sea level, water ground cover = 100%

By giving ocean floor squares a base height 1500-2000 meters below actual ocean-level we ensure that they are effectively kept as ocean.

Thus the landlike terrain types with the lowest altitudes would be submerged, and handled like shallow sea. If ocean level changes varying amounts of squares will submerge/emerge fully or partially, hiding/revealing the terrain.
This way it would not be possible to have other types of grouncover in a completely covered ocean square, but I think this makes sense. Kelp would be modelled like a ressource, only affecting production, but neither movement nor combat.

Graphics wise we would have to design tiles for above, partially above and beneath sea level for each of the basic 8 terrain types. The beneath sea level ones are easy, but perhaps it would be nice to distinguish betwen the two major types of square (landlike and ocean floor) by having varying hues of blue. Actually we could have the blue colour darken with increasing depth as calculated by: Depth = Ocean level - sqAlt - teHeight. This would give a very beautifull map.

New ideas since the posting in the map graphics thread:
There's a possible exception to this: Polar icecaps. In a way they function very much like water, completely obscuring the underlying terain. The ice cover could be modelled exactly like water. A square could be above, partially above or below ice level, which would also be a Planet attribute, but modified by a local temperature/climate zone variable. Ice on the ocean would be represented by replacing the ocean with ice. This will neglect the fact that beneath the ice there's water, which could have minor setbacks regarding movement of naval vessels, and the influence on ocean currents. But if we simply handle an icecovered square with sqAlt + teHeight < ocean level like ocean anyway this should be solved (of course while taking care of the effects of ice).

Actually we could also have local variables affect 'ocean'-level, reflecting the fact that FE the great lakes have a water level somewhat above the level of the Atlantic. These effect would however be minor, and would probably only be included becasue it would give a nice symmetrical design.

This is a new ecology proposal. It builds upon Richard's model, of course: that was pretty good, but needed to be integrated IMHO. The new model is a simplification, it also has less subsystems (like the difference between water quality and soil/land value). It might be an oversimplification and all sorts of other things might be wrong, but I leave it to you to judge. Please ask questions.

GENERAL
-------
Each map square's ecology is basically described by three numbers:

* Terrain: Basin, Flat, Rolling, Hills, Mountainous
Climate: Arctic, Sub-Arctic, Cold Temperate, Warm Temperate, Sub-Tropical, * Tropical; Ice Cap, Ocean, Sea, Lake
* Vegetation: Wasteland, Desert, Low Cover, High Cover, Light Fores, Forest, Climax Forest

5*10*7=350 combinations, some of which will be impossible. Most will be very rare.

MAP GENERATION
--------------
The map generator generates in order:

1) Height and geological specials
2) Terrain
3) Streams and sources
4) Ocean currents and Wind currents
5) Climatic zones
6) Potential Biomass (PBM) and Vegetation
7) Ecological provinces and Specials

1) Height and specials: as determined by tectonics and other geological processes: see map generator model. Geological specials, like volcanoes and geisers, ought to be generated there also.

2) Terrain

Basin: Depressions in the landscape. Only these squares can possibly become wetlands or lakes.
Flat
Rolling
Hills
Mountains

Guidelines: We need erosion rules!
75% of Earth is below 1000m.
Everything from 200m to -200m is probably flat.
Everything from 200m to 1000m is probably rolling.
Everything from 1000m to 3000m is probably hilly.
Everything above 3000m is probably mountainous.
Rivers erode their surroundings.

3) Streams and sources

Once a source is determined, the river flows downwards via the lowest possible route. The volume/turn is not much in the first square, and increases lineary until a basin (big enough, if the river will continue flowing) or sea/ocean is reached (we might put a limit on ). Rivers reaching the Ice cap become glaciers = ice covered terrain, so effectively they just stop.

Volume/turn is important for water mills and for water use in general for industry, farming, etc. Only a certain fraction (depending on the climate) of the water that is used returns to the river and it will be polluted/ carry disease/.. depending on the particular use.

The terrain of the squares the river flows through becomes on level less rough (fe hills->rolling). If the river meets another, then its volume/turn is added to the second river downstream. The first river stops there (in the second river). If a river meets itself, it forms a BIG lake or sea.

Sources don't need to be generated apart from rivers, because they are common enough to take a statistic mean. In deserts a source forms an oasis, and in basins a lake, but there they don't form a river.

Waterfalls: if they have a function (fe hindering navigability), put them in Mountain and (possibly) Hill terrain, or when the previous river square was much higher.

Navigability: Putting all navigable streams on the map can turn out to be too ambitious. In spite of that I think that is the minimum we should go for. Non-navigable rivers are so common, we simply can't include them. Their impact on fishing and water availability is also usually small enough to ignore them or handle it statistically (like sources).

Fishing and Farming: see below

4) Ocean currents and Wind currents

These currents are generated randomly. Guidelines:

Ocean currents:
On the southern half of the planet the ocean currents go from west to east (at appr. 40° latitude) and turn northwards. On the Northern half it's mirrored, but it isn't as clear there because the land masses are in the way. (coriolis effect)
Their starting point determines their temperature. Their lenght determines their force and hence their influence on the land temperature.

Wind currents:
Many of them go from the poles to the equator. They are more random than ocean currents.
Their starting point determines their temperature. Their lenght determines their force and hence their influence on the land temperature.
The 40°'s latitude (on both hemispheres) are called the 'roaring forties'(coriolis effect).

5) Climatic zone

A Arctic: pole-70°
SA Sub-Arctic: 70°-50°
CT Cool Temperate:50°-40°
WT Warm Temperate:40°-30°
ST Sub-Tropical:30°-15°
T Tropical:15°-equator

These zones are determined by latitude. They are modified by altitude (every 111m above sea level = 1 square colder) and nearby ocean currents (warm currents = warmer, cold currents = colder land).

In addition, their are climates for water-covered squares:
If these squares become uncovered, they are assigned a climate normally.

I Ice cap: Arctic squares are automatically ice-covered. It depends on their height wether they are land squares or ocean squares when the ice is removed.
O Ocean : Salt water-covered squares that are not on the continental shelf (-200 below sea level, usually).
S Sea : Salt water-covered squares that are on the continental shelf or for inland seas.
L Lake : Fresh water-covered squares. They can be at any height above sea level, but only in basin/wetland squares.

Note: If we use a cilindrical map, we could use the proportions 15-15-10-10-10-10 (or even 15-15-10-10-5-5) squares from Arctic to Tropical instead of 15-15-10-10-20-20 as indicated by the division in degrees, to correct the deformation.

6) Potential Biomass (PBM) an Biomass (BM)

Potential Biomass means the amount of vegetation a given piece of land could support.
It is a hybrid of the previous soil, water quality, NWR, PWR and farm sites in the 2.0 model. I put them together because so much things that affect soil, also affect water and farming. The exact values of the PBM and BM can be adapted to the kind of numbers that are needed by the other models, especially the economy model.

To generate the PBM, we need three things:

* Climate: already assigned, represents temperature
* Moisture: use a temporary value. It is determined by
-- Rivers : the squares with a river are much moister, those adjacent very little (eg. Nile), according to volume water/year.
-- Water currents: warm currents cause more evaporation, the condensation causes preciptiation. Cold water causes less evaporation.
-- Air currents: rain shadows
-- Climate: atmospheric convection cycles: T: large bonus, CT, SA: small bonus, WT: no bonus, A: small penalty, ST: large penalty
* Terrain: already assigned: rougher terrain means smaller PBM

The PBM in Arctic and Sub-Artic climate is limited by temperature.
The PBM in other climates is limited by moisture.
The PBM in water-covered climates is rather uniform.

***Regeneration
The game starts with the Biomass of each square equal to the PBM. Every turn if BM < PBM then the BM goes up with a small amount (relative or absolute). This amount can vary, fe in a Tropical climate this amount could be +4 to represent the fast growing and total cycle of Biomass in those climates. Or it could be dropped in this case, since these climates are evergreen.

In seasonal turns (see also Fishing and Farming): (example: Cold Temperate)

Spring--- (+2 BM, up to PBM)
Summer--- +2 BM, regeneration from winter decrease in BM
Autumn---
Winter--- -2 BM

Vegetation types.

Wasteland (nothing)
Desert (scattered)
Low Cover (grass, low herbs, creeping vegetation)
High Cover (long grass, herbs, bushes, small trees)
Light Forest (savannah, partly deforested area)
Forest (fully covered with trees)
Climax Forest (very complex and ancient ecosystems, fe rain forest)

These types might be renamed for use in water-covered Terrain (fe cover=krill, forest=kelp, climax = reef).

This depends on the BM. We have two options:
1) a certain BM equals a certain degree of vegetation, fe 35 BM is always Forest.
2) a certain ratio of BM/PBM equals a degree of vegetation

Of course some climatic zones and terrains are exempt from having a certain vegetation type, for example no trees on the Arctic Ice Cap (nothing more than desert is possible there).
No Climax Forest in the Sub-Arctic. Taiga=Forest

(You can find a potential biomap, besides other climate maps at: http://www.fao.org/WAICENT/FAOINFO/SUSTDEV/EIdirect/climate/EIsp0002.htm
There are also many good maps at: http://www-cger.nies.go.jp/grid-j/griddl.html

7)Ecological provinces and specials

Areas with the generally the same terrain, climate and vegetation become ecological provinces. These are treated as a single entity for ecological changes.

Lakes and seas are automatically one separate ecological province per entity. Rivers should also form a province apart, because the water animals have nothing to do with the surrounding terrain. Imagine an ecological province that includes the Nile and a piece of the Sahara.

Ecological provinces don't need to be in one piece. If you have five mountains separated by one square of lower terrain (with other vegetation), making them five separate ecological provinces does no good. They should be within a certain distance, however.

Important species are each (or not all of them, or maybe more) randomly assigned at the start of the game to one (or more) ecological provinces with the appropiate climate, terrain and vegetation (fe no horses in woods, or dromedaries in sub-artic forested hills). This indicates wether the animal is native in that region. If they're domesticated, they're treated as infrastructure. They automatically spread to an adjacent eco-province if it is of suitable climate, terrain and vegetation (check if provinces change or once every century). Also, they can be spread by humans (mustangs), intentionally or unintentionally (rats).

The same goes for plants, but ecological provinces can also be very well suited for the cultivation of a certain species (as a special). The species doesn't need to be native to the region, but the climate etc. must be suitable.

Reefs only in Sub-Tropical or warmer climate.
Wine and palms only in Warm Temperate or warmer.
Cereals only in Cold Temperate or warmer.
Krill and kelp only in Sub-Artic or warmer.

Some important species:
rats (spread of diseases, damage vulnerable ecosystems, eat supplies), cats, dogs
cotton, silkworm, sheep, flax, rubber, hardwood, fur animals
spices, sugar cane, coffee, tea, tobacco, cocoa; olives, figs, dates, wine, bananas, peanuts
horse, camel (cold deserts), dromedary (hot deserts), donkey (mules are infertile crossbreeds)
cereals, maize, potatoes, rice; onions, beans, soya beans, peas, lentils

Tribes and ecological provinces

When farming started, the human population was 6,000,000 and appr. 90% of the land mass was inhabited by humans. 6,000,000 people / 0.9*0.3*510,066,000 km˛ = a population of 435 people/10,000 km˛.
In The Beginning each inhabited eco-province would have its own tribe, accustomed to the climate, food and with appropriate customs to sustain themselves in that province. For example, a tribe in a hilly forest might be hunter-gatherers, while a tribe on the low-covered plains might be herders, driving around their herd; a tribe in a river ecological province might already be settled and farm minimally. Such a tribe has at most one center that is more densely populated then the average and is centre of the authority in the tribe. Those tribes might develop into civilizations at any time; they can also remain tribal, which is what most will do (until they are forced to modernize in some imperialist's empire).

On an earth-sized planet there will be appr. 13,771 squares inhabited. I suggest ecological provinces AS BIG AS POSSIBLE to keep them to a reasonable number to start with. An average size of 200 squares would give appr. 75 provinces on land mass, 25 provinces in oceans, seas, etc.

If civilizations grow beyond tribal structures, they will divide their territory into provinces. If such a province doesn't match an existing ecological province, the ecological province is simply divided into two parts: one outside and one inside the human province. They then form two separate provinces, that are checked separately for changes, since one suffers (most likely) from human influence, and the others doesn't.

EXPLOITATION
------------
Farming and Fishing essentially force the ecosystem to turn part of its Biomass into products usable by humans.

Farming is impossible in certain Terrain : Mountains, Hills (except with terracing)
Farming is impossible in certain Climates : Arctic, limited in Sub-Arctic
Farming is impossible in certain Vegetation types: Wasteland, Desert, Forest, Climax Forest

example: Cold Temperate, cycles:2 BM, regeneration: 2 BM, BM 35/48 PBM

Each turn 1 population point that is farming produces 36 * (farming tech factor: 1) = 36
and causes a decrease in BM: 36 - (4* (farming tech factor: 1)) = 32.
The Ecosystem regenerates 2: 32 + 2 = 34.

This method of farming will of course exhaust the ecosystem/fields rapidly. Another method of farming consists of farming only half of the fields, while leaving the other half fallow.

Each turn 1 population point that is farming produces 36 * (farming tech factor 0.5) = 18
and causes a decrease in BM: 36 - (4 * (farming tech factor 0.5)) = 34
The Ecosystem regenerates 2: 34 + 2 = 36.

This method of course has decreased yields, but they remain constant.

In seasons:

---------ECOLOGY-----FARMING/FISHING
------------------------------------
Spring--- +2 BM------Sowing---------
Summer--- +2 BM------Maintain Fields
Autumn---------------Harvest: -4 *(farming tech factor) BM
Winter--- -2 BM---------------------
------------------------------------

Another method is: 1/3 field summer grain, 1/3 fields winter grain, 1/3 fallow + cattle.
The varied cultures on the fields and the manure of the cattle (which is partly fed by the winter grain) reduces the need for the soil to recover. Tech factor: 2/3

Modern farming methods would have a farming tech factor of 20 or something, due to the use of pesticides, genetic engineering, very good tools, mechanization etc.

Rivers and irrigation.

So, what's the benefit of rivers in this system? A river adds a certain amount (depending on volume/year) to the regeneration of the BM each year. FE, a Cold Temperate climate square with a river on it gets +3 or +4 regeneration instead of the normal 2, due to the nutrients in the silt.
Furthermore, a river always increases the humidity of the squares it is on and consequently the PBM. Irrigation also increases humidity, except that it is a human-induced change (a terrain improvement), but the river (or a canal) only needs to be adjacent, not right on the square.

Fishing
Sea Fishing works exactly the same. The marine BM gets +1 regeneration if it is on the continental shelf (due to the nutrients washing off the land) and +2 or even +3 nearby a river mouth.
River Fishing can be treated as farming.

Hunting
Normally, farmers are supposed to supply their diet by doing a little hunting. The Ecosystem can support this. However, when they have advanced farming methods and produce their own meat, they no longer have time for hunting. But the animals eat grass and the expanded settlements need space, so its just the same for the Ecosystem.

Intensive hunting
This is usually done by commercial hunters. They can hunt a special of fur animals, or of especially abundant or easy to catch birds (dodo) until it disappears (usually within a few years). They can also intensively hunt a terrain for meat, furs, ivory,.. . The PBM is then decreases a certain number, and intensive hunting is then impossible. The specials could be exploited for a longer time, but only -very- carefully.
(examples: Bizon, many North American fur animals).

MISCELLANY
----------
-If you want to know if it snows on a square (fe alpine troops): 35° latitude is the snow limit. If it has a wet climate, then there's snow. From 70° to the pole is permafrost. From 80° to the pole is alway ice-covered. Depending on the exact position between, you could figure out in which months or seasons there's snow.

-Groundwater reserves: They are no part of the ecosystem and are therefore treated as mineral reserves. A realistic amount of regeneration of the reserves would be barely distinguishable, so if they're used, they're gone (unless they're used very carefully, just like huntable specials)
I suggest to assign the groundwater reserve to an ecological province as a whole. This simulates the huge underground streams and lakes that are stretched over great distances. Groundwater level might be a percentage of the total heigth of the terrain, so it is easy to reach in lowlands and difficult to reach in highlands.

I think some things are a bit too complicated, I'll elaborate later. But you probably already knew that . Also, the idea of ecological provinces might be obsolete with the new architecture. For right now I'm doing the economy at the map square level, and so the ecology model should be done there also. If we need to, we will agregate up levels (FE to province) later. But this model is not very computationally expensive after the world is set up, at least as far as I get from my quick read.

On the agricultural productivity stuff, if the new model is accepted, you'd have to give me info in terms of sites. The whole production model is built around that concept, so your inputs would need to be put in that context. But that shouldn't be difficult. If needed we can turn the production function inside out to see what the number of sites should be for a given level of productivity.

A few comments:

I don't think that water type should be listed as a climate. It seems like you have all ocean squares defined in the same climate, and this doesn't make sense. There can be a big difference between oceans at the equator and ones neat the arctic. Can we have Ocean and Lake be classified as terrain, and then assign then to climate zones like everything else? I'd recommend:

• Terrain: Basin, Flat, Rolling, Hills, Mountainous, Ocean, Sea, Lake
  
• Climate: Arctic, Sub-Arctic, Cold Temperate, Warm Temperate, Sub-Tropical, Tropical
  
• Vegetation: Ice Cap, Wasteland, Desert, Low Cover, High Cover, Light Forest, Forest, Climax Forest
  

quote: I suggest ecological provinces AS BIG AS POSSIBLE to keep them to a reasonable number to start with.

We were planning on dealing with this by making vast provinces in places like the Sahara and much smaller ones in places like Europe. The sahars can be two or three provinces, while places like Europe need to have a lot more. But that may be a moot point if we don't use provinces.

The rivers probably are the most complicated, they require rather much bookkeeping. If they will be placed between tiles, their turns will always be 90°. Also, many cities were created on rivers, due to trading opportunities and water supply. If they are between tiles, a river can never run through a city, or the cities should be able to occupy multiple squares (10,000 km˛) fairly early in the game. However, in that case the river will give adjacent squares at both sides a bonus to PBM due to silt. The PBM can (possibly) be further increased by irrigation. Note that irrigating a square with a PBM able to support light forest or higher vegetation will cause an increase in PBM, but farming will not benefit from that because vegetables, cereals or orchards are considered Low cover, High Cover and Light Forest. Other vegetation types can't support farming (because the trees are in the way or the crops don't grow in deserts), with possible exceptions like rubber trees. Farming consequently needs a suitable ecosystem, which forces humans to adapt it to their needs.

Eco-provinces are not really needed in game, their biggest importance is regulating the spread of species and climates when the map is generated.
Everything that happens with an eco-province can also happen with a map square if desired. However, most properties of and effects on provinces have a large area of effect, so they should affect multiple squares at once. FE 'native' animals (this just means an animal lives there in the wild, by the way), soil suitable for a specific crop (if the province disappears or changes greatly, the suitability also vanishes).

Also, the unifying factors for an ecological province are PBM and Climate. So a eco-province able to support forest could be deforestated and still remain intact in the process. Deforestation on that scale, however, would certainly reduce the PBM (of the squares), so the forest might or might not be able to regrow spontaneously; the province is not needed in any way, unless some areas are more gravely affected than others. Then it could split.

When an ecological and an economic province overlap, nothing happens at first. Only when the PBM is influenced (=permanent effect) by the humans, the provinces split: one influenced part, within the economic province and one part outside.

For PBM, I was thinking for minimum 160 for climax forest: it would then take 160 years to grow in a suitable area.

Wasteland-----0 to 5
Desert--------5 to 10
Low Cover-----10 to 20
High Cover----20 to 40
Light Forest--40 to 80
Forest--------80 to 160
Climax Forest-160 to 320

Ice Cap: I consider this desert on ocean and wasteland on land (but I believe you mentioned in this or another thread, Richard, that there was vegetation in the middle of Greenland: if so, it would also be desert or low cover.) The ecosystem on ice is very different, however: it could be considered a particular vegetation level.

I put ice, ocean, sea and lake on the climate list not because they are separate climates, but because water temperature is rather stable and the differences are not that big. There are huge krill concentrations at 40°, kelp at 20° and reefs in the tropics. I was considering them specials in large areas. These specials would then boost the PBM.

I didn't put the water types on the terrain list because that way, you can't have water(or ice)-covered mountains, basins, etc. When such a square is uncovered due to dropping sea levels, rising land mass or installing a dike, the terrain is already there and in tune with its proximity. The land PBM could be based on the sea PBM.

The water squares certainly must have an adjustment to PBM for latitude, since hotter areas have richer aquatic ecosystems.

Maximum vegetation levels for climate and water zones:
Sub-Arctic: Forest
Arctic: Low Cover
Ice: Desert
Ocean: 'High Cover'*
Sea: 'Forest'*
Lake: no limit

*These are abstractions, of course: trees don't grow on the water, but it's the same level of vegetation, not the type).
Note that ecosystems in the middle of the ocean are not particularly rich: coastal areas are the richest due to solar light that reaches the bottom and nutrients from the land.

Maximum vegetation levels for terrain:
Hills: forest
Mountain: light forest

Every basin has a chance to become a wetland, that decreases in drier climates. Every wetland has a chance to become the starting point for a river. River reduce the roughness of the terrain by 1 category, so when a river runs through flats it creates basins and those basins might become wetlands.
Wetlands in desert are oases (places with a higher PBM due to more moisture), so oases don't need to be a special, only exceptional.

If made a differentiated these types because the PBM and the type of ecology is different in these groups.

quote: 2) Terrain Basin: Depressions in the landscape. Only these squares can possibly become wetlands or lakes. Flat Rolling Hills Mountains

Also i think you should add into the specials trenches for both oceans and inland.

quote: Once a source is determined, the river flows downwards via the lowest possible route. The volume/turn is not much in the first square, and increases lineary until a basin (big enough, if the river will continue flowing) or sea/ocean is reached (we might put a limit on ). Rivers reaching the Ice cap become glaciers = ice covered terrain, so effectively they just stop. The terrain of the squares the river flows through becomes on level less rough (fe hills->rolling). If the river meets another, then its volume/turn is added to the second river downstream. The first river stops there (in the second river). If a river meets itself, it forms a BIG lake or sea.

quote: To generate the PBM, we need three things: * Climate: already assigned, represents temperature * Moisture: use a temporary value. It is determined by -- Rivers : the squares with a river are much moister, those adjacent very little (eg. Nile), according to volume water/year. -- Water currents: warm currents cause more evaporation, the condensation causes preciptiation. Cold water causes less evaporation. -- Air currents: rain shadows -- Climate: atmospheric convection cycles: T: large bonus, CT, SA: small bonus, WT: no bonus, A: small penalty, ST: large penalty * Terrain: already assigned: rougher terrain means smaller PBM

quote: Some important species: rats (spread of diseases, damage vulnerable ecosystems, eat supplies), cats, dogs cotton, silkworm, sheep, flax, rubber, hardwood, fur animals spices, sugar cane, coffee, tea, tobacco, cocoa; olives, figs, dates, wine, bananas, peanuts horse, camel (cold deserts), dromedary (hot deserts), donkey (mules are infertile crossbreeds) cereals, maize, potatoes, rice; onions, beans, soya beans, peas, lentils

quote: EXPLOITATION ------------ Farming and Fishing essentially force the ecosystem to turn part of its Biomass into products usable by humans. Farming is impossible in certain Terrain : Mountains, Hills (except with terracing) Farming is impossible in certain Climates : Arctic, limited in Sub-Arctic Farming is impossible in certain Vegetation types: Wasteland, Desert, Forest, Climax Forest

In the summer, sub-artic can grow some of the biggest crops in the world if its in the polar regions, of course that is only for 2-4 months.

Farming is possible in Deserts and Forests (atleast rainforest). Deserts if there is irrigation are among the best places for farming because the nutrients there don't get used up.

As to the rainforest, many natives in Brazil are semi-nomadic and do some farming there, but it is not standard western farming. In fact, many S.A. countries a pursuing this avenue because it can be used much longer than the traditional method of farming.

quote: Intensive hunting This is usually done by commercial hunters. They can hunt a special of fur animals, or of especially abundant or easy to catch birds (dodo) until it disappears (usually within a few years). They can also intensively hunt a terrain for meat, furs, ivory,.. . The PBM is then decreases a certain number, and intensive hunting is then impossible. The specials could be exploited for a longer time, but only -very- carefully. (examples: Bizon, many North American fur animals).

'Wetlands can occur on flat land if they are sea level. Florida is a very good example of this. As is Louisiana to a lesser extent (well before the levees were put in).'

I was thinking of 'basin' as a depression in the landscape, so if a basin was near an ocean or other wet square it would become wetland. FE The terrain gained from the sea by the Dutch (up till now) would be considered basin.

'Also i think you should add into the specials trenches for both oceans and inland.'

Here also I thought basin might cover this. But it could as well be put in the specials if that's more practical.

'One thing to add to this is that often rivers in deserts may disappear before they ever reach the coast or form a lake. Also many rivers go underground.'

Surely. Where they go underground they would add to the ground water reserves.

Since wet terrain seems problematic, if propose another categorisation.

Terrain: (Trench?,) Basin, Flat, Rolling, Hilly, Mountainous
Climate: A, SA, CT, WT, ST, T
Vegetation: W, D(also ice desert?), LC, HC, LF, F, CF
+
Water: Ice, Ocean, Sea, Lake, River, Source/Wetland

If there's much water in the terrain, one of these is applies.

'Don't know if you were going to put this here, but pollution and human habitation should impact this.'

Basically, permanent damage means adjust the PBM, temporary damage means adjust the BM. I have sketched out pollution and will post it. I don't know when, since the barbarian Deadlines are heading for my border and I have to stop them before letting myself in with the more pleasant aspects of civilized life .

'Insects should be added, but also how are we going to deal with evolution of new animals/plants. I don't want to do much, but even within human history there have been new species created, or maybe you could say sub-species moreso (Dogs and Cattle and some plants being the only truly new species).'

Farming is impossible in certain Climates : Arctic, limited in Sub-Arctic
Farming is impossible in certain Vegetation types: Wasteland, Desert, Forest, Climax Forest
[/QUOTE]
Ok the last two are wrong in some cases.

'In the summer, sub-artic can grow some of the biggest crops in the world if its in the polar regions, of course that is only for 2-4 months.'

I meant the average production for a year.

'Farming is possible in Deserts and Forests (atleast rainforest). Deserts if there is irrigation are among the best places for farming because the nutrients there don't get used up.'

Well, if desert squares are irrigated, the PBM goes up, and then they are able to support more vegetation (exactly how much depending on the circumstances).

'As to the rainforest, many natives in Brazil are semi-nomadic and do some farming there, but it is not standard western farming. In fact, many S.A. countries a pursuing this avenue because it can be used much longer than the traditional method of farming.'

I thought mainly of the classic intensive farming methods. Those tribes use other food production 'technology' in game terms, with less limits to terrain but probably also less productive.

'Should add fishing to this.'

Fishing has been proven to be more sustainable than hunting. Most likely because fish doesn't share living space with humans like land animals. Maybe hunting and fishing need a variable in the production equation that shows how much % of the land is still usable as habitat for the species.
You can go out hunting in a city but it won't be worth the effort .