Push a metal corer into a peatland and you pull up something remarkable: a dark, dense, sponge-like material made of partly decomposed plants. This peat is rich in carbon. In some places, that peat has been building up for thousands of years. Peatlands are the ecosystems where this happens.

Peat is often associated with the bogs of Scotland or Ireland, but peatlands occur on every continent, from the Arctic to the tropics. They can sit beneath open moorland, under swamp forest or in remote floodplains. What links them is water: in wet, oxygen-poor ground, dead plant material does not fully rot away, so carbon accumulates over centuries and millennia.

That makes peatlands globally important. Although they cover only about 3–4% of Earth’s land surface, they store nearly a third of the world’s soil carbon. When they remain intact, they can keep locking away carbon over very long timescales. But when they are drained or converted for agriculture, forestry or development, that stored carbon is exposed to air and released back into the atmosphere as greenhouse gases, including carbon dioxide. Thus, peatlands can become major sources of greenhouse gas emissions when degraded. Globally, peatland degradation is estimated to account for around 5–10% of annual human-caused carbon dioxide emissions.

For ecosystems so important to the global carbon cycle, we still know surprisingly little about some basic things.

Read more: How we discovered the world’s largest tropical peatland, deep in the jungles of........

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