Worldbuilding wonders

So far I’ve written about worldbuilding science for laying out entire worlds, and some unusual types of habitats. Most fiction doesn’t take place on a whole planet, or somewhere truly odd, it happens in a smaller region of an ordinary world. Even for a nearly-normal place, there are biological principles that the SFF author could use to make a locale distinctive and still plausible.

Island biogeography is one of my favorite, combining as it does migration and evolution and frequently-bizarre plants and animals.

Take an isolated habitat like an island. It might start with plants and animals on it, but once the island becomes separated from the original home ranges of those species they can’t mix with the larger population.

New species can come in through immigration, but the more isolated the island is the fewer kinds of species can get there. Isolation is relative: terrestrial mammals are a lot easier to stop than birds or marine mammals.

Original species or newly-introduced species can also go extinct on the island even if they are thriving elsewhere. Since new individuals can’t easily get there, the island populations are on their own. A small population can go extinct just by chance. Habitat change over time can also force species “off the island.”

The “island” doesn’t have to be land in the middle of an ocean, either. A lake in the middle of a continent might be an isolated habitat if you’re interested in fish. A mountaintop can be an “island” if the species can’t climb down one mountain and back up the next. Isolation is relative.

The size of the island is important too. A larger island offers more habitats so it can support a larger number of different species. A larger island might be able to support larger populations of each species, making it less likely that an individual species would go extinct.

Now comes the fun part: closed habitat (more or less), limited types and/or numbers of species, limited or abundant resources. Let the natural selection begin!

New Zealand makes a great example of what can happen on isolated islands. New Zealand separated from Gondwanaland between 80 and 100 million years ago. It started out with plenty of plants and reptiles, but if any very early mammals were present they quickly died off. (The mammals didn’t start to become dominant until 65 million years ago.)

New Zealand still has the descendant species of some of reptiles that were already there, like the tuatara – the only surviving species in its entire family. All its cousins died off about 65 million years ago.

Tuatara lizard
(via Wikipedia)

Birds could fly in, though it was a long trip. Without pesky mammals to eat eggs and compete for food, many of the bird species didn’t even need to fly once they settled in. Flying is an expensive skill, so it was entirely lost in some species. Because all of these birds evolved in isolation, they are found only on New Zealand. Many have gone extinct since European colonization: at least 43 species, or a third of the total number of birds.

Kiwi bird
(via Wikipedia)

The kiwi is a national symbol, but there were many more distinctive birds. The harpagornis, the largest eagle known to have ever existed, lived on the flightless birds like the moa, and died out not long after Maori settlement when the moa were hunted out.

Birds evolved to fill the roles that mammals would occupy in most other places. The largest known eagle (now extinct) lived on New Zealand.

Giant eagle
(via Wikipedia)

Since New Zealand started out without mammals, only the species that could travel long distances through or over the ocean got there. There are plenty of aquatic mammals, like whales, dolphins, seals, and sea lions. These species are not isolated from their parent populations.

Short-tailed bat
(via Wikipedia)

The only terrestrial mammals present on the island before humans arrived were three species of bats. The birds don’t fly, but the mammals do. Like the birds, the short-tailed bats adapted to the lack of ground mammals and evolved to crawl around on the ground as well as fly. They could tuck their wings away and scamper around like mice.

Once people started coming to New Zealand, another pathway for intentional and unintentional plant and animal introductions opened up. The Maori brought some species from 1250 or so, most notably the Polynesian rat and the domesticated dog.

After Europeans discovered the islands in 1769, they brought all sorts of animals: pigs for food, mice and rats accidentally, weasels and ferrets to catch the rats, possums for fur. These adaptable mammals have driven many of the native New Zealand species to extinction, and have threatened most of the rest. Conservation efforts are trying to reduce or eliminate these invaders. One such project led to the removal of 30 tons of dead possums from one of the smaller islands.

Back from science to fiction: I see all sorts of possibilities here. Some part of your created world could be isolated from the rest, and thus distinctive. One human colony or space ship could be isolated from the rest, allowing the humans and their attendant species to evolve in ways unlike the main human population. Or the entire human population could fragment into smaller isolated populations.

And what about accidental introductions, either by human settlers or alien visitors? What if we accidentally introduce rats to a space station? Or aliens introduce their scavenger species to London? What species go along with colonists, intentionally or accidentally, and what effects do those have on the native populations?

My brain is fizzing with ideas for alien ecosystems. I hope yours is too.

You can follow any responses to this entry through the RSS 2.0 feed.
You can leave a response, or trackback from your own site.