Vegetation, Climate, Ecology, and Pollution

[Mannheim Tanker]

There is some good stuff here in this model. Now for my "but..." I apologize in advance if I sound like I'm nitpicking - I'm not. I just think the goal of this model is getting muddled and mired in too much detail.
First, I think we all need to take a step back and outline the GOAL of this model (as we well should with all of the models). Then, model things so that you meet that goal. I think everyone started this model with several things in mind, and the details just started to pile up. In the end, you also have to remember that scientists spend entire careers modeling just little pieces of the entire system that we're trying to model here Consequently, I think we should strive for an overall, general model, and just add a few details that add to the flavor of the game. Otherwise, many of these details will ultimately contradict one another and just confuse things (and the players!) later on.

Some more points:
1. I think we're off track when modeling vegetation types based on "soil". The distribution of vegetation is based more on availability of water (not directly linked to soil, although there IS a small connection there), growing degree days (GDD), and latitude. Compounding this, elevation had an effect by simulating increases in latitude. I forget the actual #, but there is a rule of thumb that says every increase in 1000ft elevation above 2000 ft = 10 degrees of latitude (or something close to that). This means that you CAN have forests on mountain tops. For example, in Arizona, that is the one of the few places where you'll find them, as the higher elevations get more water, and it is cooler there. Also, the treeline in the artic is dicated more by GDD and the permafrost than availability of soil.

Another point: It's not entirely correct to say that deforestation at point x, will result in Y land cover type with Z effect on farmers. The main point to deforestation is the loss of biodiversity, as this greatly increases susceptibility to disease and natural/manmade disasters. Compounding this, diversity increases as you enter the tropics, but those soils are typically VERY nutrient poor. The reason deforestation in the tropics is bad news, is that removal of the forests usually means the total loss of what little nutrients were there in the first place (the only reason they remained there when forested, was because detritus/dead matter was immediately reincorporated into the system). Temperate regions are less susceptible to loss in diversity, since they have less to begin with, and the species there are better adapted to live in a monoculture (eg the Artic). Not to say that man can't have an impact there! Also, while man can "destroy" the ecology of the landscape, something will nearly always return (I can point out the nuclear test grounds in Nevada that have lots of regeneration). The impacts on MAN are usually more severe, and are what should be our focus. Here's a possible solution for the model:

1. As human populations increase, the impact on the environment increases.
2. The effects of this should be mostly negative. Even fertilization has its negative effects (non-point source pollution).
3. Tech advances in environmentally friendly techniques (and for example, less road building), coupled to social advances in environmentalism can reduce these effects.

I point out roads, since the fragmentation of the natural environment is one of the biggest problems that man brings to natural systems. It makes it harder for many species to migrate (both plants and animals - yes, plants DO migrate!) Also, I think the solution is as much social as it is scientific.

As you can see, this is a VERY complex model, and we will never do it justice by modeling all of the details. That's why I say we shoot for a general overview. This is a long posting, and I've still only scratched the surface. If you're interested, I can point you to several good sources of information on this subject (ecosystem modeling) from the basic to VERY scientific/technical. I won't even touch on the social aspects of environmental science, since that's a can of worms that I don't intend to open (too much politics involved!)

[Henrique Duarte]

Mannheim Tanker

In the spirit of aiming towards the goal I think that to your description of the main effects of deforestation you must add erosion alteration in sensible climates:
The main geological effect of flora cover is the fixation of soil and the reduction of erosion. Any deforestated zone is prone to an higher rate of soil loss and if you are in a delicate climate drastic changes can happen.
example: I specifficaly think that any civ that tempers with natural flora (either through deforestation or herding) neighbouring semi-desertic areas should pay the consequences : southern spain/Portugal and the Sahara desert were the examples I wrote somewhere before (I think I wrote this in another topic)

[Mannheim Tanker]

I agree wholeheartedly. That's the point that I wanted to make - we need to describe how humans influence the environment, and in turn how that impacts future generations. It seems to me that many of the details in the model focus too much on the minute details of how humans influence the environment. Sorry if I didn't make that clear...I didn't really go into too many details, because I think that we must first go back over the main framework of the model and THEN put the details back in. Right now, I think that it's premature to model every last detail, when we haven't defined exactly what it is we're trying to model. I think we can forget about modeling every last detail, because that's too impractical.

I'm thinking along the lines of this:
1. Civs start off with natural environment
2. Environment starts to change as civs grow
3. Changes in environment affect how civs grow
4. This in turn affects social and tech pressures within civ
5. Civs either continue on current course or change actions to affect their impact on the land.

It should not be an easy feat to guide your civ along environmentally friendly paths as long as market forces guide your development (as opposed to spiritual forces, as with the American natives). Keep in mind that even the Native Americans greatly influenced the landscape, but much less so than the Europeans that arrived in 1500. The tradeoff was their level of expansion...

Once the overall model is defined, we can then go ahead and start adding some of the details outlined in previous posts.

[Richard Bruns]

The goal of the model is to make simple system that creates a dynamic game environment while using a minimum of processor time. There are only three things that change with any frequency: Soil, Water, and Vegetation. In some rare cases, the climate will change and the map generation routines will be run again.

This is all we need to create a dynamic map, represent farming yields, and show the result of ecological disturbances. We are not trying to run a complex simulation that models the myriad arcane causes of what happens to the environment.

Mannheim Tanker:

You say that we should make a "an overall, general model" and complain that we have too much detail, and then you launch into a long, detailed analysis of biodiversity, animal migrations, and other things that simply won't affect a civilization. Do you actually want us to include all of that stuff? The current model is not entirely accurate, but it is a simple way of tracking environmental changes that are important to the player.

Which details that we currently have do you think are unneeded?

By the way, Soil is not just the properties of the dirt in the area. As I wrote before, “Soil” is a term that includes every geological and chemical influence on plant growth in that area. This includes permafrost, slope of the land, nutrient availability, and the physical properties of the growing medium. These things have a big impact on the kinds of vegetation that can grow in an area.

Henrique: We have already included all of the stuff you wrote about.
[This message has been edited by Richard Bruns (edited May 30, 2000).]

[Mannheim Tanker]

Richard: First, I'm sorry if you felt that I was attacking your model - I wasn't. If you reread the first line of my initial response, you'll see that I really like most of the model Second, although it's natural to want to defend one's baby, you should take care as to not make your response/defense personal - we need all the people we can get in this project, and super-defensive responses like that just tend to alienate new faces (and maybe even the old-timers). Fortunately, I'm not a new face here - in fact I think I've been working on Clash longer than most of the people here (except maybe Mark and F Smith!). You all know me from this forum as Paul Crocker - I just can't find my other password, so I'm using the login from work instead

I was asked to comment on this model, since my background is in environmental science, and I have real world experience in dealing with cleaning up civilization's crap left on the landscape I'll address your concerns one at a time here:

1. I wasn't advocating modeling biodiversity, etc at all! Just the opposite actually. I listed all that stuff to show you how complicated this beast COULD be. I apologize if I didn't make that point clear enough (I knew that was going to happen before I even typed it!)

2. As far as too much detail, I was referring to discussions on modeling the influences of "soils". Soil science can be immensely complicated (I still have nightmares of my soils classes, now that this subject has come up). I guess I just didn't pick up on the nuances you were trying to include in modeling "soils". My fault or yours, it doesn't matter. I think the important point is that we must really generalize this aspect...such as overuse in arid regions = bad. overuse in temperate regions = not good, but not so bad as in arid regions. We could take an OO approach on modeling this, or use an algorithm. Not sure which is best...I just think that saying, soil in northern regions is worse/more fragile than in southern regions is incorrect. The Red River Valley has some of the richest land on earth, and it is much farther north than the "fertile" soil of the Mississippi Valley

3. The same goes for blanket rules regarding forest distribution. This is dictated much more by moisture than by "soil". You can really grow a forest anywhere if you have enough moisture. "Soils" does have an effect, but is irrelevant if the moisture isn't there.

4. Wind patterns are tough to model. We have the world's fourth largest supercomputer here at Stennis Space Center, and IT has trouble modeling ocean and air currents accurately The generalized atmospheric model was meant to model the occurence of the ICTZ's that occur at certain latitudes. This could happen on any M Class planet, not just earth

To summarize, I'm not attacking the model, just pointing out areas that really need tweaking if you want to model real world phenomena. It IS a game, but if you are going to put something in this type of game, your goal should be to at least partially mimic something that's really happening out there. You are already on the right track with the model - Henrique and I are just pointing out some areas that need some refinement. As far as my "expert" opinion goes, you can either take it or leave it...I only comment on those areas with which I'm quite familiar (I'll leave the economics to those experts!). In the end, having a realistic climate/environmental model will definitely help separate Clash for the other games in this genre.

[Lord God Jinnai]

Mannheim (Or should I say Paul )
4. Wind patterns are tough to model. We have the world's fourth largest supercomputer here at Stennis Space Center, and IT has trouble modeling ocean and air currents accurately The generalized atmospheric model was meant to model the occurence of the ICTZ's that occur at certain latitudes. This could happen on any M Class planet, not just earth
-----
Basically for this section from what I understand this will pretty much be calculated 1 time, before the game starts and only a few times later if ness and then only in small regions. Same goes for ocean currents.

[Richard Bruns]

Mannheim Tanker: I'm sorry I sounded harsh. I was just trying to respond to all of the points you brought up in the post and ask you what you were proposing. I assume that if someone talks about something in that much detail, they want it to be modelled in the game. I guess I do need to learn how to be more diplomatic.

I know that Soil is a bit of a kludge, but I couldn't think of anything better. There is more to the environment than Climate and Water; I wanted to put something in that represented the terrain's physical ability to support life. There are some places, like cleared rainforests, that have plenty of water and a good climate but bad physical conditions for growing crops.

I figured that I could just wrap up a lot of complicated things in that one variable with a quality value from zero to eight. Anything that affects the land, like pollution or strip mining, simply changes this value. I probably should have come up with a better name for the variable, however. I explained what it was, but the explanation apparently wasn't obvious enough.

I never said that soil in northern regions is worse. The soil restrictions are only for Arctic and Sub-Arctic terrain, latitudes greater than 55 degrees. The good farmland in the US is around 40 degrees north. These restrictions are modeling the permafrost and ice that keep things from growing well.

We are not trying to make accurate models of dynamic wind and water patterns. I figured on drawing a few dozen simple linear direction vectors, letting them alter things once, and then forgetting about them.

[Richard Bruns]

Sorry, double post. The forum program doesn't always get along with my school computer network.
[This message has been edited by Richard Bruns (edited May 31, 2000).]

[Mannheim Tanker]

LGJ: Paul who? He has been assimilated into the Mannheim Collective

You are correct in describing what I had envisioned for the "wind" model. It would probably be too hard on the clock cycles to calculate every turn. I brought it up in my model as a method of determining the distribution of moisture/deserts, and therefore, indirectly, the distribution of different land cover types. I hadn't given much thought to ocean currents...not sure how they would affect civs. Maybe someone can enlighten me if I'm missing something really big here. Also, Henrique, please butt in at any time if I'm out of line with my thinking in this model! My area of expertise is more along the lines of land cover (especially vegetation), and less so in the plate tectonics area of the model. It's my understanding from our past correspondance that you have tons of info to offer in this regard.

[Lord God Jinnai]

The 2 things I know right now that ocean currents will affect are:

1. Hurricane movement

2. Climate, ie bringing warmer water morth, cooler water south. The beakdown of these would affect tempatures then.

[Mark_Everson]

Richard:

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.

Hope this is what you need... For resources I would just wing it for now. Sites will usually be in the range from 1-10.

[Richard Bruns]

This is Version 2 of the ecology model. It has quite a few changes based on the discussions about the first version.

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.

There are several big environmental changes that can happen naturally. Changes in the activity of the sun can change the climate zones, which would change farm effectiveness everywhere as well as altering a lot of the natural environment. Some places would become uninhabitable, while others would be better places to live. This would prompt a lot of migrations and other upheavals. It should happen at most two or three times per game, but I think that it would be a lot of fun to deal with.
[This message has been edited by Richard Bruns (edited June 08, 2000).]

[Lord God Jinnai]

Rich:
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.
-----
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.
-----
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.
-----
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.
-----
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.
-----
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.)
-----
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.
-----
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.
-----
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:
-----
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.
-----
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.
-----
Hmmm. I wonder. What about future technologies being able to permantly reclaim land from the sea, although over a descent time period.


There are several big environmental changes that can happen naturally. Changes in the activity of the sun can change the climate zones, which would change farm effectiveness everywhere as well as altering a lot of the natural environment. Some places would become uninhabitable, while others would be better places to live. This would prompt a lot of migrations and other upheavals. It should happen at most two or three times per game, but I think that it would be a lot of fun to deal with.
-----
Also volcanoes and earthquakes. Volcanoes should increase the soil content around them after each eruption. Also earthquakes can raise and lower land, in addition to normal stresses over time. Both of these should be included, but will be based more on the plate techtonics model (although volcanoes can appear in other areas like Hawaii and earthquakes can be in mid-continet like New Madrid).

[Richard Bruns]

Responding to LGJ's comments, in order:

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.

Volcanoes and earthquakes are not part of this model, but their effects are. I will have to work with Toubado_Koomi on the places where the ecology and disaster models interact.

[Lord God Jinnai]

In latitueds 0-12, there are very dry places. In fact the one of the driest places on earth lies in that area, right next to the wettest.