climate line | As the planet warms, forests around the world are losing resilience and becoming more vulnerable to disturbance. That’s especially true for ecosystems in tropical, temperate and arid regions of the world, according to a new study.
When a forest loses its resilience, it means it gradually loses its ability to recover after fires, droughts, logging and other destructive events, studypublished on July 13 in nature. After a certain point, some forests may be approaching some kind of tipping point—a threshold that causes them to decline rapidly.
Beyond that, some studies suggest that forests may not fully recover at all. Instead, it may completely transform into other ecosystems, such as grasslands or savannas.
In recent years, the concept of forest tipping points has become a hot topic in climate science. The vast Amazon rainforest is one of the most worrying subjects.
Large swathes of the Amazon are already affected by chronic deforestation. Now, many scientists are warning that climate change is making things worse. Reduced rainfall, increased drought and devastating wildfires are taking their toll on the iconic rainforest.
Some modelling studies suggest that continued global warming — coupled with continued deforestation and other human disturbances — will eventually send the Amazon through a point of no return. Beyond this threshold, ecosystems may enter an unstoppable decline spiral, ultimately transforming from lush tropical rainforest to lush savanna.
There is considerable debate about where exactly this tipping point is. A major recent report from the Intergovernmental Panel on Climate Change summarizing the best and latest climate science around the world says the Amazon may reach a tipping point by the end of the century. But it also noted that there is still a lot of uncertainty about how likely that is.
A jaw-dropping study in the journal shortly after the IPCC report natural climate change warns that Amazon has lost its resilience for at least a few decades (climate line, March 8). That means it’s nearing its so-called tipping point — although the study’s authors say immediate action to protect the rainforest and curb climate change could still save it.
Now, scientists are turning to the rest of the world. This week’s research looks at forests across the globe, from warm tropical regions to boreal forests in northern Canada and Russia.
A research team led by Giovanni Forzieri of the University of Florence, Italy, used machine learning techniques to analyze 20 years of global vegetation data from 2000 to 2020. They used satellite data on ecosystem productivity — an indicator of tree health — to assess how quickly and easily forests recover from disturbance.
They found that many boreal boreal forests were actually regaining their resilience. The researchers believe that warming and rising carbon dioxide levels may offset other negative impacts of climate change in these regions—at least for now.
Still, even some boreal forests are experiencing localized loss of resilience, including parts of central Russia and western Canada.
The situation elsewhere is bleak. The resilience of forests in tropical, temperate and arid regions of the world is declining significantly.
Intact forests — forests that are not managed or harvested by humans — tend to have higher baseline resilience levels. Still, both intact and managed forests are losing resilience at a similar rate over time.
This suggests to scientists that the decline has nothing to do with human management techniques. They may be driven by climate change.
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