Forests
Biomes · Structure · Ecology · Deforestation — Tabulated by the Bureau, illustrated from field plates.
The Wooden Globe
Forests cover 31% of Earth's land surface — about 4.06 billion hectares. They store ~660 gigatonnes of carbon, more than the entire atmosphere holds. They are home to 80% of terrestrial biodiversity.
"In every walk with nature, one receives far more than he seeks." — John Muir, 1877
The Three Great Forests
BOREAL · Taiga
Spruce, pine, larch. -50°C winters. Russia, Canada, Scandinavia. Largest biome on land — 1/3 of global forest cover. Home to wolverine, lynx, brown bear.
TEMPERATE
Oak, beech, maple. Four seasons, deciduous. Eastern US, Europe, NE Asia. Most heavily fragmented by human history.
TROPICAL
Year-round warmth and rain. Amazon, Congo, SE Asia. ~50% of all species live here on 6% of land area.
The Vertical Forest
A mature tropical rainforest stratifies into five layers, each with its own species, light regime, and humidity.
- Emergent 45–55m · kapok, harpy eagle
- Canopy 30–45m · 70% of species, sloth, toucan
- Understory 5–20m · jaguar, boa, palms
- Shrub layer 1–5m · ferns, saplings
- Forest floor <1m · 1–2% sunlight, decomposers
Coast Redwood
Sequoia sempervirens — the tallest tree on Earth. "Hyperion," discovered 2006 in Redwood National Park, stands 115.92m. Some living individuals exceed 2,200 years. Bark up to 30cm thick, fire-resistant, tannin-stained red. Confined now to a narrow fog belt of northern California.
Logged from 2 million acres to ~110,000 acres of old growth between 1850 and 1965.
The Amazon
5.5 million km² across nine countries. Generates ~half of its own rainfall through evapotranspiration. Holds an estimated 390 billion individual trees of 16,000 species. Indigenous reserves cover 28% — and have the lowest deforestation rates.
Biologists Thomas Lovejoy and Carlos Nobre warn of a "tipping point" at 20–25% loss, beyond which the eastern Amazon flips to savanna. Deforestation as of 2022: ~17%.
The Boreal Belt
Stretches uninterrupted across Russia (Siberia), Scandinavia, Alaska, and Canada — 1.4 billion hectares. Permafrost beneath. Stores ~30% of terrestrial carbon, mostly in soil and peat. Vulnerable to fire: the 2021 Siberian fires released more CO₂ than Germany's annual emissions.
The Wood-Wide Web
Beneath every healthy forest runs a fungal internet. Mycorrhizal networks (genus Rhizopogon, Suillus, etc.) connect tree roots, trading sugar for soil nutrients. Forester Suzanne Simard demonstrated in 1997 that mother trees pump carbon to nearby seedlings of their own species through this network.
A single teaspoon of forest soil contains kilometres of fungal hyphae.
The Cutting
Drivers: cattle (Brazil), palm oil (Indonesia, Malaysia), soy (Cerrado), cocoa (West Africa), illegal logging (Southeast Asia, Central Africa). Madagascar has lost 90% of its primary forest since human arrival; only the lemur-bearing eastern fragments remain.
One Hectare, One Thousand Species
Field surveys in Yasuní National Park, Ecuador, recorded 655 tree species in a single hectare — more than the entire United States and Canada combined. The same plot held 100,000 insect species per hectare, more bat species than all of North America, and the territories of harpy eagles, jaguars, and white-bellied spider monkeys.
Costa Rica's Reversal
From 75% forest cover (1940) to 21% (1987) — and back to 60% by 2022. The first tropical country to reverse deforestation. Mechanisms: a 1996 PES (payments for ecosystem services) program, ecotourism, ban on hunting, phaseout of cattle subsidies.
"Reforestation is the cheapest, fastest carbon-removal tool we have." — Daniel Janzen, ecologist of Guanacaste
Our Planet — Jungles
Attenborough narrates the courtship of birds-of-paradise, leafcutter agriculture, the night chorus of the Costa Rican cloud forest. The most-watched nature episode in history.
Anatomy of a Leaf
The factory of the forest. Each square cm of leaf surface holds millions of chloroplasts — bright-green organelles fixing carbon at ~6 CO₂ per second under full sun.
Stomata on the underside open to admit CO₂ and release O₂; close to conserve water. Leaves shed in autumn as the tree reabsorbs nitrogen, leaving carotenoids (orange) and anthocyanins (red).
To Plant a Tree
"The best time to plant a tree was twenty years ago. The second-best time is now." — proverb, often Chinese-attributed
A planted forest is not a wild forest, and a wild forest cannot be replaced in a human lifetime. But the act of planting is a vote for a future you will not live to see — the radical optimism of foresters from Wangari Maathai's Green Belt Movement (51 million trees, Kenya) to the Bonn Challenge (350 million hectares pledged by 2030).