Tropical forests are losing their ability to store carbon. “What more of a wake-up call do we need?”

By Chris Lang

According to research published in Nature, one of the most worrying impacts of the climate crisis has already started. Tropical forests are losing their ability to absorb carbon. The research found that the Amazon could stop being a carbon sink as soon as 2035.

For the last three decades the amount of carbon absorbed by the world’s tropical forests has decreased. In the 1990s tropical forests removed about 4.6 billion tonnes of carbon from the atmosphere each year, about 17% of carbon dioxide emissions. In the last decade, that figure fell to 2.5 billion tonnes, about 6% of global emissions.

Consequences for policies intended to stabilize Earth’s climate

The paper does not specifically mention REDD, but the abstract concludes that,

Overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth’s climate.

Simon Lewis, Professor at the School of Geography at Leeds University, was one of the lead authors of the research. He describes the research as “the most worrying paper I’ve written.”

Forest offsets: “A marketing tool”

He told the Guardian that,

“Humans have been lucky so far, as tropical forests are mopping up lots of our pollution, but they can’t keep doing that indefinitely. We need to curb fossil fuel emissions before the global carbon cycle starts working against us. The time for action is now.

“There is a lot of talk about offsetting, but the reality is that every country and every sector needs to reach zero emissions, with any small amount of residual emissions needing to be removed from the atmosphere. The use of forests as an offset is largely a marketing tool for companies to try to continue with business as usual.”

Doug Parr, Greenpeace UK’s chief scientist, told the Guardian that,

“That forests are now seemingly losing the ability to absorb pollution is alarming. What more of a wake-up call do we need?”

The study tracked 300,000 trees over a period of 30 years in 565 forest plots in Africa and the Amazon. Almost 100 research institutions took part in the research. The scientists measured the diameter and estimated the height of the trees. They returned every few years and tracked the changes in carbon storage in the plots. They used a statistical model and trends in CO₂ emissions, temperature and rainfall to estimate changes in forest carbon storage up to 2040.

REDD-Monitor has reported several times on the dangers of tropical forests tipping from a sink to a source:

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Obviously we need to protect tropical forests. We have to address what Lewis calls “the immediate threats to tropical forests”: deforestation, logging and fires. We also have to leave fossil fuels in the ground to address the climate crisis, which is having a severe impact on tropical forests.

The conclusion of this latest paper in Nature is that tropical forests are losing their ability to store carbon. Given this risk, it makes no sense to offset continued emissions from burning fossil fuels against forest carbon. Yet that is precisely what REDD proponents and the aviation industry are proposing.