Deforestation leaves voids in the Amazon rainforest that are easily spotted by satellite, but more subtle degradation from logging and farming can be harder for scientists to catalog. Now two Michigan State University researchers have reunited to bring this latter threat to the rainforest into sharper focus.
“If we’re only looking at deforestation, we’re only seeing half the problem,” said David Skole, a professor in MSU’s Department of Forestry. “There’s an equivalent or greater amount of degradation.”
Rainforest becomes degraded when its health is compromised without it vanishing, as would be the case with wholesale deforestation. Logging and farming operations can cut and burn underlying vegetation while leaving larger canopies of trees in place. Satellites are thus hampered from capturing the degradation occurring beneath from above.
So Skole teamed up with his former graduate student Eraldo Matricardi, now an associate professor at the University of Brasilia, to perform the most comprehensive study of rainforest degradation in the Amazon to date. Using digital image processing, they pored over pixels from thousands of satellite images spanning 25 years and the entire rainforest.
They found that, over the past 2 1/2-decades, the area of degraded forest surpasses that which has been lost to deforestation. Publishing their work online on Sept. 10 in the journal Science, the researchers also showed that degradation is continuing at a higher clip than deforestation.
Deforestation had dropped off in recent years thanks to Brazilian policy change. “But these policies did little to influence forest degradation,” Skole said. “That just kept going.”
“Degradation has been rising a lot over the last decade,” Matricardi agreed. “This is important because these degraded forests are losing their potential to support ecosystems and biodiversity.”
The consequences of degradation are similar to those of deforestation. Beyond ecosystem loss, they both result in more greenhouse gas in the atmosphere and lead to the spread of infectious disease, the researchers said. Malaria, for example, can explode near deforestation or degradation.
For those reasons, world leaders have pledged to fight both deforestation and degradation in international accords, including the Paris climate agreement and the Biodiversity Convention.
Now, the paper’s findings are challenging some assumptions that could help researchers and policymakers better understand the reality of the Amazon.
For example, one current theory suggests that degradation is often a precursor to deforestation, meaning that if scientists track deforestation, they are essentially monitoring degradation as well. The new data does not support this hypothesis.
“Degradation has to be handled by policy separately,” Skole said. “It cannot be included as a subset of deforestation.”
The data also offers insights into last year’s devastating fires in the Amazon. Some people have speculated that degradation alone could account for the historic blazes. Degraded areas are more susceptible to burning, Matricardi said, but it’s not the complete picture. The team’s observations suggest more people are starting more fires to clear more forest, Skole said. In light of the Brazilian government’s recent relaxation of Amazon protections, he doesn’t see things getting better.
“It’s going to happen again this year, more than likely,” he said. “And soon.”
Brazil has already shown that policies informed by data can tame troubling trends in the Amazon. Between 2003 and 2004, the Amazon rainforest lost nearly 30,000 square kilometers of rainforest to deforestation annually, an area larger than the state of Vermont. With support — and pressure — from the international community, Brazil pushed that number below 6,000 square kilometers over the course of a decade.
Skole hopes the new paper will help put forest degradation on the same track. “It’s genuinely out there as evidence to influence policies on managing the Amazon forests,” he said. “There needs to be active efforts monitoring degradation.”
This paper shares tools and methods that scientists and government agencies can use to monitor degradation, as well as take on critical but more nuanced questions, the researchers said. For example, how much of the degradation comes from government sanctioned farming and logging compared to illegal operations?
Matricardi said the study does not answer that question, but he suspects illegal contributions account for as much as half of forest degradation. “That must be curbed by the government and environmental agencies,” he said.
The researchers submitted an early version of their paper months ago to try and get the information out ahead of this year’s fire season. When the pandemic hit, the team persevered through revisions and additional complex data analysis, using remote data servers and meeting with each other multiple times a week over Zoom and WhatsApp.
But perhaps that shouldn’t be surprising. After all, whether they are in Michigan or Brazil, that is what Spartans do.
(Note for media: Please include a link to the original paper in online coverage: https://science.sciencemag.org/content/369/6509/1378.full)