Building Biomes

Legend tells of an ancient sword, crafted of silver and etched in the runes of giants, the only blade capable of smiting the evil threatening to consume the land. The last known wielder of this blade was a powerful warlock, who long since disappeared into the wilderness. Undeterred, our intrepid hero sets off to find him, marching across a craggy desert until her boots wear thin against the sand, fighting off the threat of thirst and the brutal sun beating down upon her back, until at last she sees it. A forest of pine trees looms on the horizon, their black needles both ominous and —

What a minute, a pine forest? What is that doing out here?

Why Pine Forests Don’t Grow in Deserts

Ecology is the study of how organisms interact with both living and non-living components of their environment. In its most general terms, the ecology of a plant or animal species tells us why it lives in one place and not another, usually because of adaptations it’s developed for a particular environment over evolutionary time.

Pine trees, for example are largely found in cold, windy habitats with seasonal snow. Such conditions help us to describe their biome.

What’s a Biome?

Simply put, a biome is a category of habitat.

Map of biomes around the world.
Photo: Wikimedia Commons

You’re no doubt already familiar with many of the major terrestrial biomes: tropical rainforest, desert, tundra, etc. Though we might have a general idea of what each of these settings look like, how do we classify them from a scientific standpoint?

It’s ridiculously simple. Biomes are determined by the temperature of a location and how much rainfall, or precipitation, it receives. We can visualize conditions in our terrestrial biomes using a very simple graph of temperature versus precipitation.

Graph of how terrestrial biomes map onto temperature and precipitation.
Photo: Wikimedia Commons

Here we can see tropical rainforest is characterized by high temperatures and lots of rainfall. Tundra has cold temperatures and little rainfall.

Why are temperature and precipitation important for separating one biome from another? These are the major factors that determine what plants can grow in an area. Plants, in turn, determine how a habitat is structured and what food/shelter is available to animals.

What determines these patterns in temperature and precipitation around the globe? We’ll dive into deeper details about weather and climate in a future topic. For now, know that global climate patterns follow a large-scale gradient of latitude (hotter at the equator, colder near the poles), with more regional variation created by wind patterns and landscape features such as mountains and oceans.

Notice also that I keep saying terrestrial biomes. Habitats within freshwater or saltwater have their own, slightly more intricate classification scheme, which we’ll explore in a future post.

Major Terrestrial Biomes

Now we know the basics: biomes are classified based on temperature and precipitation in a location, which determines what plants live there, which determines what animals live there. Where this gets neat from a worldbuilding perspective is once we dive into the specialized adaptations that suit plants and animals to survival in their biomes. Showcasing these adaptations — whether on real or fictional organisms — can make your setting feel like a living system, rather than mere words thrown together on a page.

With that, let’s take a look at some features of the major terrestrial biomes!

Tropical Rainforest

It’s hot. It’s humid. It rains a lot.

Confined to the equator here on Earth, climate in tropical rainforests is extremely stable, with little to no variation across seasons. Because of these prime living conditions, tropical rainforests are the most species-rich habitats on Earth. A towering canopy of trees creates a variety of vertical habitats for species to specialize on — some canopy-dwellers, like orchids, may go their entire life without touching the ground!

Layers of the rainforest.
Photo: DK findout!

The canopy of the rainforest is open and bright, while the understory faces severe shade limitations. Understory plants have large, dark-green leaves to increase their light absorption, and specialized drip tips allow excess water to run off without waterlogging the leaves.

Drip tip of an understory rainforest plant.

Temperate Rainforest

In my humble opinion? Optimal mystical forest potential!

Typified by the majestic redwood forests of northeastern North America, temperate rainforests get a lot of rain but with cooler temperatures than their tropical counterparts. Redwoods are the tallest trees on Earth. They are, in fact, so tall that they’re incapable of pumping water all the way up from their roots, and so depend on frequent fog to absorb into their upper needles.

When redwood trees fall or die, they’re often able to sprout new growth around their trunks. Over time, these sprouts may form a ring of redwood trees known as a fairy circle — a great place to hunker down or try out a dark ritual!

Redwood fairy circle, or cathedral tree, in Prairie Creek Redwoods State Park.
Photo: M. D. Vaden

Temperate Deciduous Forest

Here’s your classic medieval fantasy forest. Deciduous describes trees that lose their leaves during part of the year, entering a dormant state. This is a useful adaptation because of the seasonality that typifies the temperate deciduous forest. Summers are warm and wet and good for growing, while winters are cold and dry.

Fawn over an adorable baby deer in spring. Frolic through the flowery meadows in summer. Tap a bucket of maple syrup in fall. Tumble into an icy river in winter. So many options!

Fall foliage in a temperate deciduous forest in New Hampshire.
Phot: bluepoint Flickr

Tropical Grassland (Savanna)

Typified by the African savanna, tropical grasslands are warm with relatively little rainfall, making tree cover sparse. Instead, vast grasslands support some of the richest diversity of megafauna, aka large mammals, anywhere on the planet. Life in savannas tends to congregate around watering holes, which may vary in availability seasonally.

Elephants are an important ecosystem engineer on the savanna, meaning they create habitats used by many other species. Specifically, elephants dig out watering holes with their tusks that provide an important resources for many other plants and animals.

African elephants at a watering hole.
Photo: Bjørn Christian Tørrissen

Temperate Grassland (Prairie)

Like the tropical grassland, temperate grassland is typified by relatively little rainfall and a large diversity of grass species. The temperate side to this grassland means it’s much colder, receiving snow and pretty brutal cold during the winter. The classic temperate grassland is the prairie of middle North America.

Remember how the African savannah is renowned for its megafauna diversity? North American prairies have a few big mammals — bison, pronghorn antelope — but honestly, it’s underwhelming. That wasn’t always the case. During the Pleistocene Period, North America boasted just as impressive a menagerie of large animals, including cheetahs, lions, camels, wooly rhinos, and ground sloths. Can you imagine what the landscape might look like with some of those animals still around? Maybe your fantasy novel could!

Illustration: Roger Hall


My native biome, shrublands are known by many names throughout the world: chaparral in California, fynbos in South Africa, mattoral in Spain, kwongan in Australia. All these habitats are characterized by hot, drought summers and relatively mild, wet winters. Many shrubs of this biome are aromatic, such as white sage, which is used for smudging rituals by indigenous communities.

California chaparral near Pinnacles National Park.
Photo: Vadim Manuylov

Shrublands naturally experience frequent fire, and many plants are adapted to getting singed. Pine trees with serotinous cones only open after a fire has burned through, clearing space for new seeds to sprout. Shrubs such as manzanita can quickly re-sprout from below-ground, even if their branches are burned away. For shrub systems, frequent and low-intensity fires are healthy, clearing out old growth and making space for the new.

In the 21st century, we’ve seen an increase in devastatingly destructive megafires in places like California and Australia, owing to a long history of fire suppression. By preventing small fires from occurring, dead debris builds up, and the fire that eventually erupts burns out of control. Many indigenous cultures purposefully set small fires to keep their landscape healthy, but these practices were banned and vilified by the Eurocentric view that all fires were bad. Acknowledging the importance of natural fire regimes and cultural burning practices will be an important step for mitigating future fires.


The defining feature of a desert is lack of water.

For most people, a hot desert is likely the first to come to mind. Few plant and animal species are able to survive in such an extreme environment. For animals, water efficiency is key, such as the water-storing hump of a camel or the incredibly efficient kidneys of a kangaroo rat. To beat the heat, animals have light coloration and often hide away during the day, coming out at night when it’s cooler.

Desert plants also cool off with light coloration, and by placing their delicate leaves high above the hot ground. Water efficiency is crucial, achieved by reducing leaf surface area and storing water in trunks and branches. The baobab is a real-life tree that looks like it belongs in a fantasy world, and it has many of the features we’ve just discussed!

Baobab trees in Morondava, Madagascar.
Photo: Gavinevans

While hot deserts get all the attention, deserts can also occur in cold places. The Gobi desert in Mongolia, Atacama region of Peru and Chile, and the Great Basin of the United States all have hot summers but frigid winters, making them some of the harshest places on Earth!

Boreal Forest

Compared to a temperate deciduous forest, an evergreen forest is also seasonal, but with a much colder and harsher winter and shorter summer season. The forest here is dominated by pines, firs, and other evergreen trees that keep their needles all year long. Many of these trees have a cone shape that allows snow to easily fall off without breaking branches.

As forests goes, boreal often wins out for the spooky factor, with dense pine trees and whispering needles easily creating an ominous vibe. This is also the land of some of our larger mammals, such as moose, wolves, and bears.

Boreal forest in Banff National Park.
Photo: Ferenc Cegledi


Located in polar habitats and remote mountaintops, the tundra is cold, windy, and gets very little rainfall. Trees don’t make it this far, usually thanks to a layer of permafrost, or permanent ice in the soil that prevents deep roots from growing. The plants of the tundra are small, hardy, and hunker close to the ground to avoid the wind.

Siberian tundra during summer.
Photo: Dr. Andreas Hugentobler

One of the most seasonal of habitats, polar tundras experience brutally cold winters where the sun may set for upwards of several months, leaving the land in complete darkness. Summers are still relatively chilly, but here the sun may rise for several months of constant daylight. I spent two months in Barrow, Alaska one summer and never saw the sun set once. It was weird. Because of this intense seasonality, many animals (especially birds) of the tundra are migratory, taking advantage of the sunny summer, then flying south to temperate or tropical areas for the winter.

Breaking the Biology

Now you know how to make biomes work in your book. What if you’d rather make them not work? For dramatic effect, of course.

Let’s revisit our pine forest from the opening example. Sure, a desert or savannah has nowhere near the conditions necessary to naturally support pine trees — too hot, not enough rainfall. What if the warlock’s presence has created a magical chill, allowing these ominous trees to grow? Maybe the trees on the edges are withered and brown, becoming more dense and dark deeper into the forest.

So the next time you’re fleshing out your setting, take a moment to consider what biome it’s in. Whether your goal is to imitate the real world or complete a fantastical alternative, incorporating the diversity of biomes and the adaptations suited for life in each are a great way to bring your written habitats to life.

Maybe you even feel like inventing a biome of your own? Perhaps a giant mushroom forest? Or maybe a crystal desert? I’d love to hear about them in the comments below, or feel free to ask any questions about the habitats in your story!

Looking for more writing tips?

Why bother with biology?

Fiction or non-fiction. Fantasy realism or alien worlds. Knowing some basics of biology can help make your world believable — or not!

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