There are more than eight hundred definitions of “forest,” and we’re going to cover them all. I’m kidding, but if you’re like many, you simply write “forest” in your stories and leave it at that. Here’s a chance to be a little more specific and populate a world with different types of forests.
The tree types are covered in more detail in Creating Life (The Art of World Building, #1), but it helps to know the basic types: evergreen (literally green all year), coniferous (needle-like leaves), and deciduous (seasonal loss of leaves, flowers, and fruit ripening). All trees actually lose their leaves but deciduous ones do so all at once in dry or winter seasons. The others lose and replace their leaves continually. Coniferous trees are the tallest in the world, including the redwood, so if we have elves that are living in enormous trees, they are conifers, which also means a single straight trunk.
Most of the time, we will indeed want to say a forest is just a forest. Only when choosing something more specific, as defined next, will we need to deviate.
A forest typically has a tree canopy covering 60-100% of the land within it. This allows for some underbrush but not something impenetrable. Half of the Earth’s trees are in the northern temperate zone, though this is partly because there’s so little land in the southern temperate zone. Temperate zones have both evergreen and deciduous forests; evergreens are the most common trees unless it’s very cold temperate, where conifers dominate.
The latitudes between 53-67° (Polar Regions) have boreal forest, which are predominantly coniferous, with some deciduous trees.
Tropical rainforests are found within 10° of the equator and are almost the only kind of forest found there; the trees there are considered evergreens. Jungles are found there as well (see below). Smaller winged creatures can fly beneath the tall tree-canopy of rainforests but might find it difficult to reach the open sky unless a clearing is available. There is very little underbrush due to the canopy preventing sunlight from reaching the ground.
A woodland has less tree density and therefore less canopy than a forest and is relatively sunny, with only a little shade. Otherwise the tree types are similar to forests. Most people probably think they’re the same as forests and might call them “light forests.” When naming forested areas, “Forest X” vs. “Woods X” can be used interchangeably, regardless of the tree density. In our notes about the area, we might want to specify it’s a woodland.
A woodland will be easier to ride horses or other animals through than a forest or jungle. The sparser underbrush limits ambush opportunities, so an animal or humanoid species we’ve invented and which relies on ambushing prey is less likely to be found here. While animal trails will still exist, the sparse underbrush means life doesn’t need an existing path (created by other animals) quite as much.
A savannah has virtually no tree canopy despite the trees, which is one reason grass covers the land. This results in more grazing opportunities for animals than in forests. Some people wrongly believe that widely spaced trees indicate a savannah, but some savannahs have more trees per square mile than forests do. Savannahs cover a fifth of the world’s land surface and typically lie in an area between forest and grasslands.
There have been times in human history where we’ve set fire to a savannah on purpose. The goal is to prevent a forest from forming by killing the smaller trees and shrubs, maintaining the open canopy.
Animals that hide in tall grass will use a savannah to their advantage. Some of their prey will be skilled at climbing trees to escape. The lack of underbrush means riding animals or driving a caravan of wagons is easy.
The term “jungle” is poorly defined in its vernacular usage. It’s basically a very dense forest with enough underbrush to be difficult, if not impossible, to traverse unless we hack our way through. It’s often implied to be in the tropics but needn’t be. This contrasts with rainforests, which have very little underbrush due to the tree canopy that prevents light from reaching the ground. Jungles often border rain forests due to the light at the edge allowing underbrush to grow; we might have to cut our way through a jungle to reach the rain forest. The wildlife in jungles is dependent on where the jungle lies.
If you’re confused as to the difference between jungle and rainforest, that’s partly because the latter term replaced the former. To quote Wikipedia, “Because European explorers initially travelled through tropical rainforests largely by river, the dense, tangled vegetation lining the stream banks gave a misleading impression that such jungle conditions existed throughout the entire forest. As a result, it was wrongly assumed that the entire forest was impenetrable jungle.”
Due to underbrush, a jungle is largely impassable so that even people on foot will have trouble. Horses or other steeds cannot be ridden and might even be abandoned. Creatures who ambush will abound in such conditions.