I had two experiences not so long ago that really brought home to me the magnitude of nature's profusion, and the difficulty of portraying this in fiction. First, I took my family on a camping trip to Big Basin State Park, where we spent four marvelous days in a tent cabin and hiking through the redwood forest. Second, I started reading Watership Down aloud to my children.
I don't know how many of you have hiked in the California redwood forests, but to me this is a magical environment that I associate with my childhood. I have been back every year for the past four years or so with my family, but this time was the first time I'd been back in the rain, and before we even left on the trip I was very excited: I had a strong feeling we'd see different things in the rain from what would be there in the dry weather. I was right. On our first day's hike we counted forty-three banana slugs, after seeing perhaps one or two total over the past four years! We ended up at a total of sixty-four for the trip as a whole, plus two salamanders, and any number of earthworms and spiders. We also saw at least two species of squirrels, several bluejays, two bird species I couldn't name... but no raccoons this time, or coyotes.
The sheer number of plant species was another thing that struck me. Very seldom do you find a place where there is only a redwood tree, and some bark around it, and nothing else. There are the little sorrels, that look like giant clovers. There's the poison oak, but there's also the oak. And the madrone trees, and the huckleberry bushes, the fungi, the lichens, the mosses, the ferns etc, etc... You find tons of different plants, so many you can't name them all (unless you're a naturalist). I highly recommend you go out into nature and check out a really diverse ecosystem - it will certainly remind you how limited your garden is! And you might get some terrific ideas for ecosystems in your world. I was reminded that I have some wilderness/forest sequences planned for a later novel, and that I must go back and make sure of a few things:
1. they must be sufficiently diverse
2. they must be difficult to navigate
3. they must have different conditions in different weathers
In Watership Down, I'm continually amazed at how many different plants, trees and birds Richard Adams mentions as he goes along. Yew, furze, sainfoin, brambles, bracken, elder bloom, hemlock, dandelion, nut bushes, beech trees, birch trees, etc., etc... It makes for a very rich sense of place, and a clear view of the rabbits' awareness of their surroundings, what is edible, etc. On the other hand, this place is very specific - it's in England. When we're working with a secondary world, we can't use these terms, because presumably the ecosystem of our world isn't the same as that of England's downs! So do we make up a lot of other alien or fantasy words and let them stand in for these terms? What if we confuse people?
There's a degree of trust involved in reading any novel. I have to trust Richard Adams that all these plants actually live in the place he tells me they do. In a secondary world, I can put in a few new terms, so long as I make clear what role they play - whether they're plants or animals or birds. Once I get to a certain point, though, the reader won't want to go with me. I think the best way to approach this is through the eye of the protagonist. If the protagonist isn't familiar with any of the plants, then he or she probably won't notice many of them, and won't name any of them. He or she will probably describe them and refer to them with descriptive shorthand. But even if your character is a botanist and and knows all the plants by name, there's no point in having that person call up each and every name all the time. Only use the names when it's important to the plot that your character pay attention. On the other hand, it's valuable to consider that you won't want to describe just a single plant species at each level of tree/bush/groundcover, since diversity is what natural ecosystems are all about. It's a good idea to give a sense of mixture and variety by mixing up the shapes, colors and textures of the surrounding plant life. As for animal life, you can benefit a lot from thinking through food webs and how the species of the area interrelate. If your characters are somehow interfering in some natural process of the animals (hunting, or finding shelter or mates, etc.) then they'll be more likely to run into trouble than if they're simply moving through an animal's territory. After all, people don't run into animals for no reason. They either are seen as a food source, or have provided an additional food source (as when raccoons, jays, or bears come around looking for scraps), or have trespassed on the animal's den, etc. intentionally or inadvertently.
I came away from my trip really hoping that I can give more richness and excitement to a forest environment the next time I get to write one. I'm looking forward to it!