Global warming warning for peatlands

Global - peat TD Farm
RIGHT: Peatland in Scotland. (Photo: Alex Whittle)

GLOBAL warming will cause peatlands to absorb more carbon over the coming decades, but the effect will decline after 2100 if warming continues.

An international team of 70 scientists led by the University of Exeter says after this so-called negative feedback – where climate change causes effects that slow further climate change – will increase.

In environments such as forests, carbon from dead plants decomposes and is released into the atmosphere. But in peatlands, water slows this process and locks in carbon.

Most peatlands are in cold climates and there warmer temperatures will lengthen the growing season for plants – meaning more plant matter falling into peat bogs.

Boglands on the island of Ireland make up about five per cent of the landscape and are home to rare plants and animals.

Researcher Angela Gallego-Sala of the University of Exeter says the initial increase in carbon storage, estimated to be about five per cent, will be offset by reduced storage in tropical peatlands in places such as Borneo and the Amazon region.

“Plants living in cold-climate peatlands have it tough for most of the year, but rising global temperatures will give them a longer growing season,” she says.

“Decomposition in peatlands will speed up as the climate warms – meaning more carbon and methane released – but the overall effect in these high-latitude regions will be increased storage of carbon.”

However, she says, as warming continues, tropical peatlands will

store less carbon because de-composition will speed up, while higher temperatures will not boost plant growth.

The researchers looked at a range of estimates for future warming – from an average warming of between 1°C and 3.7°C by 2100.

Modelled future projections under all scenarios suggest the present-day global carbon sink in peatlands will increase slightly until about 2100 but will then decline.

In both cases, decomposition in the tropics will overturn gains in the higher latitudes due to a lengthening growing season.

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