Most forests are less able to cope with hazards under climate change

The study also suggests that climate change has pushed 23% of the world’s natural boreal and tropical forests close to their ecological tipping point – meaning that they may not survive future disturbances.

Both conservation and climate change policies should account for this fall in resilience, say the researchers. Forests regulate the water cycle, protect soil and conserve biodiversity, and absorb one-third of anthropogenic carbon emissions.

Policymakers often depend upon forests’ carbon-absorbing powers to help meet climate change targets. But, as the research shows, climate change itself threatens forests.

The study, led by the European Commission’s Joint Research Centre, provides new evidence of climate change’s effects on forests around the world. Its researchers applied a machine-learning algorithm to satellite images of the Earth’s vegetation taken between 2000 and 2020.

The algorithm assessed how quickly forests recovered from external disruptions, based on changes in greenness in the images and in relation to the climate.

Recovery rates became slower over the 20-year period for most forests, indicating falling resilience. Tropical, arid and temperate forests were most affected, due to water shortages and increased climate variability.

The picture was more mixed for boreal forests, found in colder, northern parts of the globe. The majority, however, became more resilient. The beneficial warming and CO₂ fertilisation effect (i.e. the speeding up of photosynthesis) outweigh the negative impacts of climate change on these forests.

But the overall picture for the world’s forests is one of declining resilience. The researchers observed these patterns in both managed forests and forests that are not managed or harvested by humans.

Slowing recovery rates can act as a warning sign that a forest is getting closer to a tipping point – a position where the forest begins to rapidly decline and can struggle to recover from even small disturbances. In this vulnerable state, the forest may not fully recover and could transform into a different ecosystem, such as grassland.

The study’s results show that nearly a quarter – 23% – of unmanaged boreal and tropical forests are already extremely close to their tipping point, as indicated by their slow recovery rates from disturbance. This vulnerable share of forests, 93% of which is tropical, locks away 3.32 petagrams of carbon. This is about three times more than the amount of carbon lost through deforestation in the Brazilian Amazon over the past ten years.

The researchers point out that these critical conditions do not guarantee in themselves that a forest will transform into a different ecosystem. They are, however, a strong indicator of increasingly unstable and vulnerable forests.

They suggest that their study supports the need to adopt ‘resilience thinking’ – managing the environment for resilience – if we are to solve forest management challenges in times of rapid climatic change.

Source:

Forzieri, G., Dakos, V., McDowell, N.G., Ramdane, A. and Cescatti, A.  (2022) Emerging signals of declining forest resilience under climate change. Nature, 608, 534–539. Available from: https://doi.org/10.1038/s41586-022-04959-9

To cite this article/service:

“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.