When is an island an island?

[james_davis_nicoll]

Useful factoid: If recall Wilson correctly, if you assume all other factors stay the same, the number of species a given region per unit area can support is proportional to the square root of the total area. If, for example, you have two islands, one 10 units in area and the other 1000 units, the second one will usually have about 10x as many species per unit area and presumably about 1000x as many species in total. 100 small islands might have as much area as one big one but they will only a tenth as many species.

Does anyone here know what conditions are necessary to disconnect adjacent regions? Obviously water will do it, esp deep water. Roads and wide clear cuts can, since they make migration more difficult.

Obviously, this rule of thumb implies that a few large preserves are probably a more effective tool for species preservation than a lot of little ones.

It also implies large cities should have more species/area in them than small ones. I wonder if that is the case or if other factors (like the relative youth of large cities as common habitats) dominate?

It also means that in the Reefs of Space setting, bigger rocks will tend to be more various places to live (in terms of life) than little rocks. OTOH, delicate lifeforms might find small islands nice places to live, thanks to the lack of various competators and predators.

Comments

[nancylebov.livejournal.com]

I'm not sure that the rule is going to apply as strongly in space as it does on earth--on earth, most living things are where they are because they were able to travel there on their own. People in cities are a special case, but I'm not sure how you'd define the different types--it's fair to say that you get more diversity in cities but how would you measure it?

In space, most living things get to whereever as the result of human action. This means that you could have some asteroids set up as nature preserves (and you probably should--now, how might they go entertainingly wrong?) and others of the same size with relatively simple ecologies, though no doubt not quite as simple as the powers that be would prefer.

[james-nicoll.livejournal.com]

I was assuming that we'd build migration in.

We might not. For one thing, charging for the genetic patents is probably easier if the product isn't spreading itself around.

[nancylebov.livejournal.com]

Build migration in? As in no habit of quarantine, and let the organisms land where they may? I can't imagine most cultures derived from modernity doing that, though I can see one or two fringe cultures doing no-quarantine and being distrusted by the rest as a result.

[james-nicoll.livejournal.com]

Why not? It's all waste land at the moment.

[nancylebov.livejournal.com]

Why not what? Not have quarantines? Because when an asteroid is developed, it's not wasteland any more, and people might be edgy about
pests and diseases getting into their settlements.