Archive

Posts Tagged ‘worldbuilding’

Leaf it to me

I live in the northeastern United States, so this time of year I think about leaves a lot. The color changes are the most obvious reason to be thinking about leaves, of course. In the autumn, the trees slow down and then stop producing chlorophyll, the green pigment needed for photosynthesis, so the yellow pigments also in the leaf become more prominent.

DSC08161

But it’s probably more complicated (and more interesting) than that: yellow leaves are a sign of disease during most of the year, so some insects are attracted to plants with yellow leaves. If a tree is already ill, it might be more vulnerable as insect food. It appears that some trees actually produce red pigments to hide the yellow pigments since the green pigments are no longer doing so, and it’s all to protect themselves from insects.

DSC08259

And it’s probably really even more complicated than that, too.

(I love science: it’s always more complicated, and we’re always wrong, but it’s so much fun to try to figure it out.)

So there’s one thing to think about when world-building: does your local plant-equivalent have seasonal changes in the coloration of its leaf-equivalents? If so, why? Does that have any other effects that matter in the ecology of the world, like attracting or repelling other organisms?

For that matter, are they green to start with? Most planets with life will need some way to convert solar energy into biochemical energy, which is what photosynthesis does. There are organisms that use geothermal energy or non-biological chemical energy, but most energy comes from the sun through photosynthesis. It seems likely that other planets will have the same energetic basis (but there’s plenty of room for speculation here).

And what else do leaves do? They’re flat so they can maximize sun exposure, and they’re thin so they can maximize gas exchange.

Except where conditions are less than ideal.

Desert plants have all sorts of leaf adaptations to make sure that they don’t lose too much moisture from that flat surface. Waxy coatings hold moisture inside, and hairs cut down on air movement across the surface of the leaf, reducing evaporation. Smaller leaves help reduce water loss too.

(Leaves have to take in carbon dioxide for photosynthesis, but that creates a way that water can be lost. Grasses and cacti have evolved different physiologies to deal with that problem, but I want to stick to shape instead of biochemistry.)

Very cold can be a lot like very dry, and some of the same leaf adaptations show up in arctic climates: hairs, waxy coatings, and especially having small leaves such as like pine needles.

Leaves in wet climates tend to have fewer teeth on the edges, while leaves from cold areas have more teeth.

In places where it’s warm and wet year-round, there isn’t usually a season when most plants lose their leaves simultaneously. In temperate climates, it’s cheaper for the plant to shed them than it is to maintain them through the winter. In seasonally-dry areas, plants might drop their leaves for the dry season, again to save resources. But in very hard environments, especially if they are low in nutrients, plants often keep their leaves year-round, even through the winter, because resources might not be available to replace them.

These are broad generalizations, and there are lots of exceptions, but for the world-builder matching leaf shape to climate can provide a quick hook for a realistic world. We’re used to certain kinds of plants in certain places, even if we don’t think about it.

Putting spruce tree-equivalents in cold areas, plants with small hairy leaves in deserts and plants with large leaves in jungles makes those areas feel right to the reader, so you can save the weird stuff for where it matters. Getting the little subtle things correct keeps from jarring the reader out of your world, and makes the big things seem more believable.

DSC08390

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.