Forests still cover roughly a third of the planet's land, but they are not spread evenly. Most of the world's trees are concentrated in a few enormous forest regions, and a surprising amount of that total sits not in the steamy tropics but in the cold north. Here are the largest forests on Earth, why they grow where they do, and how to recognise each one from satellite imagery.
First, what counts as a forest
Ranking forests by size is slightly slippery, because it depends on whether you count a single continuous forest or an entire forest biome that stretches across many countries. We will treat the great forest regions as the unit, since that is how they appear from space: vast, continuous canopies that ignore national borders.
The boreal forest, or taiga
The largest forest on Earth is the boreal forest, known by its Russian name, the taiga. It forms an almost unbroken belt of spruce, pine, fir, and larch that circles the entire Northern Hemisphere across Russia, Scandinavia, Canada, and Alaska. Taken together, the boreal zone is the largest land biome on the planet and holds a huge share of the world's trees and stored carbon.
The single biggest block is the Russian taiga, which sweeps across Siberia for thousands of kilometres. The boreal grows where summers are short and winters brutally cold, conditions that favour hardy, needle-leaved conifers over broadleaf trees. From above it reads as a dark green-grey expanse, dotted with countless lakes and bogs left behind by retreating ice.
Why so much forest is in the cold north
It surprises many people that the largest forest is not a rainforest. The reason is partly geography: there is simply far more land at the right latitudes in the Northern Hemisphere than in the south, where the same band of ocean is almost all sea. Conifers are also superbly adapted to the cold. Their needles resist frost and dry winter winds, and their conical shape sheds snow, letting them blanket land that is too harsh for almost anything else.
The Amazon Rainforest
The Amazon is the largest tropical rainforest in the world, covering well over five million square kilometres across nine South American countries, with roughly sixty percent of it in Brazil. It is drained by the Amazon River, which carries more water than the next several largest rivers combined, and it holds an outsized share of the planet's known plant and animal species.
From space the Amazon is an unbroken deep-green carpet, threaded by the brown, looping ribbon of the river and its tributaries. Along its edges, the straight lines and fishbone patterns of cleared land mark where roads and farms are eating into the forest, a pattern that is sadly easy to spot from orbit.
The Congo Basin and other giants
The second largest tropical rainforest is the Congo Basin in Central Africa, covering around three and a half million square kilometres across six countries, with the largest share in the Democratic Republic of the Congo. It is one of the planet's great carbon sinks and home to forest elephants, gorillas, and bonobos. Beyond it, a few more forests stand out for scale and character:
- The rainforests of New Guinea form the third largest contiguous block of tropical forest on Earth.
- The Valdivian temperate rainforest of southern Chile and Argentina is one of the few large temperate rainforests in the Southern Hemisphere.
- The Tongass in Alaska is the largest national forest in the United States, a cool, wet, coastal temperate rainforest.
Telling them apart from above
The big forests look different from orbit. Boreal forest is darker, greyer, broken up by water and snow for much of the year, and fades into open tundra at its northern edge. Tropical rainforest is a richer, more uniform green, usually wrapped in cloud and laced with big muddy rivers. The contrast at a forest's edge, where canopy meets farmland or grassland, is often the sharpest line on the whole image.
Recognising a biome from its colour and texture is a real advantage in a satellite guessing game. Drop into an endless dark conifer forest pocked with lakes and you are probably in the far north; drop into a humid green canopy split by a brown river and you are likely in the tropics. Put it to the test in EarthGuessr.