By gathering a variety of information, a unified scoring system can be developed: Similar to the way a doctor checks a person’s weight, heart rate, blood pressure, and cholesterol, forest health can now be examined under a magnifying glass.
Different areas, different problems
Diseases of the forest are as diverse as human diseases. They all “experience different stresses on different timescales,” said co-author Katia Fernandez, an Amazon fire and drought expert at the University of Arkansas.
Tropical rainforest conditions vary from one continent to another. There are more wildfires in Africa than anywhere else. The Amazon rainforest is drying up faster than the Asian forests. Forest productivity declined significantly across the Amazon region, while productivity in the Congo remained stable. It is even increasing in China’s tropical forests due to significant reforestation efforts on the one hand and recovery from previous deforestation on the other.
Meanwhile in Asia, currently the damage due to land use change is greater than that due to climate change. In Central Africa, forests experience greater water loss and higher temperatures than in Asia.
Congo is largely intact today. The consequences of climate change are also clear here – many trees in Gabon, for example, produce less fruit, meaning less food for some wildlife – but there has been no significant tree death here. According to scientists, one reason may be that water shortages have been a problem in Africa for so long and forests are becoming increasingly used for drought.
So far, it seems, “the situation in Congo appears to be fine because people are cleaning there less intensively than elsewhere, and the increased dryness in the atmosphere isn’t enough to damage the trees,” Covey said. Drought can make them grow faster due to less clouds and more sunlight on the plants.
Amazon is the most risky
The fact that the Amazon remains the most polluted region according to the new measurement method doesn’t surprise anyone on the team. “Even when viewed in conjunction with other global rainforest challenges, the Amazon is extremely vulnerable,” Covey said. “Deforestation and climate change have a significant impact on the functioning of entire ecosystems.”
The richness and biodiversity of the Amazon is unmatched with golden lion tomato lions, colorful birds and giant bees. Ten percent of the world’s species live here, alone more than two million insect species. The trees and soil in the area store the equivalent of four or five years of human carbon emissions. Forests produce much of their own water, absorbing moisture from the Atlantic Ocean through the soil and vegetation and returning it to the atmosphere through the leaves. One water molecule can pass through a forest four to five times.
Deforestation has increased under Brazilian President Jair Bolsonaro, reaching a 12-year high last year. Fast-growing, drought-resistant trees repel species that thrive in moisture. Rainfall is getting heavier and causing flooding. Droughts last longer and occur more frequently – there have been three major droughts in the last 16 years. The fire blazed explosively, and the forest mortality increased.
All of this led two researchers to conclude in 2017 that unless deforestation and fossil fuel burning stopped, major changes to the moisture cycle would occur in parts of the Amazon. They can destroy millions of trees or turn forests into dry forests. Their assumption: A tipping point could occur if only 20 percent of the Amazon was cut down. Roughly speaking, this already happened today.
The authors – Thomas Lovejoy, professor at George Mason University and senior fellow at the United Nations Foundation, and Carlos Nobre, senior researcher at the University of São Paulo – are co-authors of the new study.
Saatchi said deforestation must be stopped at all costs. But this alone is not enough to stop the negative development. Active reforestation is urgently needed. “We don’t know yet how the system will react and how quickly. However, it is best not to wait for this development to take place completely. We have to restore this system.”
By combining all of these measurements, scientists were for the first time able to paint a clearer, if more disturbing, picture of the state of tropical forests. While the measurements largely confirmed what other scientists had expected, the new study is “more concerning because it makes more sense,” said Nate McDowell, a forester and geologist at the Pacific Northwest National Laboratory, who was not part of the research team.
“The collaborators on this project, especially the lead author, are known to be very, very careful,” McDowell said. “The results are troubling: As the planet warms, some areas of forest approach threshold-like behavior. The system is slowing down.”
However, it is not too late to change course. The Saatchi team hopes that the new complex analysis will convince people of how severely ecosystem changes can affect us all. They also hope that the results of their research will be used to monitor further change — and direct resources toward recovery.
–
