Which continent is the Amazon rainforest in?

South America, spread across nine countries with about 60 per cent in Brazil. It holds something like a tenth of all known species on Earth, and new ones are described at a rate of roughly one every other day - which is a statement about how little of it has been examined rather than about how fast life is diversifying.

The description of it as the lungs of the planet is misleading and worth correcting. A mature forest is close to carbon-neutral in respiration terms: it produces oxygen by day and consumes much of it as leaf litter and organisms decompose. Its real climate importance is as a carbon store - hundreds of billions of tonnes locked in wood and soil - and as a rain engine, recycling moisture back into the air and generating flying rivers that carry water to the farmland of southern Brazil and Argentina.

The concern is a tipping point rather than gradual loss. Enough of that recycling depends on the forest itself that clearing beyond some threshold - often estimated around 20 to 25 per cent, and roughly 17 per cent has gone - could dry the system into savannah over large areas without anyone cutting another tree. Parts of the southeastern Amazon have already been measured emitting more carbon than they absorb.