Vegetation, Climate, Ecology, and Pollution

[Richard Bruns]

I am officially putting this model on hold. I will be concentrating in technology, population, and learning Java until after Demo 5 is completed.

Whenever I continue work on this model, it will probably include the map generator model (plate tectonics, terrain and resource placement, etc.) No one else is currently working on that and it already has a lot of overlap with the ecology model.
[This message has been edited by Richard Bruns (edited September 16, 2000).]

[Richard Bruns]

Okay, my last post is now null and void. The ecology model has unexpectedly shifted from neutral directly to fifth gear and I won't be available to drive it due to real life commitments.

Most of the posted stuff is very out of date.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!

[/Ridiculous Melodrama Mode]

[Mark_Everson]

Well, I don't have any grand unifying plan at this point, but rather a couple of comments / bits of info assuming we base what we use on Richard's model.

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.

2. Richard had a way in here to handle irrigation that is different from what I had in the econ model. In econ, irrigation was treated as just another capital expenditure on farming. For those familiar with the econ model, irrigation potential would boost the tech factor T above normal, allowing for additional investments that improved productivity. When the initial OO models in this area come out, I will check to see if they're consistent with what I think is the best way to handle this, and comment at that time.

[Richard Bruns]

There is a lot of Ecology discussion in the Mapsquare Class OO discussion thread. The core of our ecology model will most likely come out of that discussion.

[Beör]

I think the basics of the ecology model are sound, but for the purpose of Demo5 I think we need a plan for a simple, maybe slightly modified version of Richards model.

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.

Later we could include dynamic ecological changes one-by-one

[Beör]

LGJ and I have discussed some basic map graphics issues in the map graphics thread. I'll crosspost some of my ideas here, since it is very relevant to the ecology model. At present LGJ has not had an opportunity to respond, so blame it all on me.

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.

The modelling of water/ice this way will also allow for slow changes in underlying terrain. In coastal areas hills that are partially submerged by rising water-level can gradually loose teHeight, disappearing completely. Mountains covered in ice can gradually loose height and become more like foothills.

[This message has been edited by Beör (edited October 05, 2000).]

[Richard Bruns]

Sounds good. I like the idea. But we need to distinguish between surface movement and submerged movement. Kelp can impact the movement and combat of submarines. And when the player starts building undersea colonies, they should be able to interact with the ocean like they could with land.

[4VAlien]

Gaining land from the sea is such a good idea.. as dutchmen i would really love to see it. Just the dike as square improvement is a good idea

[Simon Loverix]

Hi guys,

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/S...e/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 km² = a population of 435 people/10,000 km².
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.

-My next post will handle pollution.

[Mark_Everson]

Wow, Simon good stuff! I've only been able to give it a cursory read, and only have a few minutes, so I can only comment on a general level.

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.

What does everyone else think on the model?

[Richard Bruns]

This looks good overall. Thanks for taking it on.

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.

We may decide to have rivers run between squares instead of through them. Keep this in mind when dealing with their effects.

[Simon Loverix]

Thanks for the comments.

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 km²) 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

This post is almost as long as the previous one.
[This message has been edited by Simon Loverix (edited April 18, 2001).]

[Simon Loverix]

I just had an idea about wetlands!
They are essentially one-square rivers (only a source).

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.

I think this makes the model more integrated.
[This message has been edited by Simon Loverix (edited April 18, 2001).]

[LDiCesare]

I'm being silly, but...
What is the difference between ocean and sea? Do you mean open water and coastal water?

[Simon Loverix]

Exactly. Ocean means deep, open sea. Sea could be either an inland sea of limited depth or coastal sea on the continental shelf. Both of these are salt water. Lake has fresh water.

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

Silly questions don't exist, only silly answers .