The tropical rainforest of the Congo basin is the world's second-largest (after the Amazon) and the world's largest terrestrial carbon sink. Water drains via the Congo river into the Atlantic from six countries: the two Congos, Cameroon, the Central African Republic, Equatorial Guinea and Gabon. It absorbs an estimated 600m more tonnes of carbon dioxide than it emits each year, roughly equivalent to the annual emissions of Germany.
Scientists affiliated with the CongoPeat project, led by Simon Lewis of the University of Leeds, have mapped vast carbon-rich peatlands spanning almost 17m hectares -- a larger area than England and Wales combined. Collectively these peatlands store carbon equivalent to roughly three years of global emissions from the burning of fossil fuels.
The basin hosts approximately 1,200 bird, 700 fish, 450 mammal and 280 reptile species. Western lowland gorillas, found across central Africa, differ significantly from their larger mountain gorilla cousins: they groom less, socialise less and enjoy a more varied diet. Some gorilla hand gestures are specific to a given area, akin to accents.
Forest elephants, smaller than the savannah elephants of east Africa, act as "ecosystem engineers". By trampling smaller trees and spreading the seeds of larger ones, they indirectly influence the climate: one study estimates that without them, carbon capture in Congo's forests would be 7% lower. Herds return to the same forest clearings (called "bais") over many decades, passing the information down generations.
Mysterious clearings in the forest known as bais function as ecological entrepots. In 2024 a team led by Evan Hockridge at Harvard used lidar to map more than 2,000 bais in Odzala-Kokoua National Park in the Republic of Congo -- many times more than were previously assumed to exist.
Salt pans used by the Mboko and Kota peoples around 150-200 years ago have been found in the forest. Initial digs by a Franco-Congolese team found Neolithic axes (2,500-4,000 years old) and quartz tools possibly dating to the late stone age (10,000 years ago). The site could illuminate the Bantu expansion -- the migration of black Africans from west-central Africa to the rest of the continent, 4,000-6,000 years ago.
From 1990 to 2020 the basin lost 8.5% of its total forest area. The World Bank estimates that the forest supplies $1.15trn a year in global benefits, largely climate-related -- roughly six times the GDP of the countries that contain it.
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