ecology

If atmospheric oxygen rose from 21% to 42%, paper would catch fire from a single spark, lightning storms would ignite vast wildfires, and giant insects might become possible — but the world would be a tinderbox.

Insects pollinate roughly three-quarters of food crop types, recycle dead plants and animals, aerate soil, and feed countless animals. If they vanished overnight, terrestrial ecosystems would unravel within a few years and most of agriculture would fail.

Biodiversity is not evenly spread across the planet. Seventeen 'megadiverse' countries, most of them tropical, hold a large share of Earth's known species. This ranking uses IUCN Red List endemism data and explains why counting species country by country is so hard.

Species are disappearing tens to hundreds of times faster than the long-run average, and monitored wildlife populations have fallen by about three-quarters since 1970. Here is what the numbers mean, what drives the loss, and what has worked.