An index to classify the vulnerability of rainforests to climate and human impact
Scientists at NASA’s Jet Propulsion Laboratory (JPL) in Southern California and other international research institutions have created the Tropical Rainforest Vulnerability Index. This indicator will reveal and assess the vulnerability of these diverse ecosystems to two main categories of threats: warming and dry climates, and the consequences of human land use, such as deforestation and fragmentation due to invading roads, agricultural fields and logging.
The index shows that the world’s three major rainforest regions have varying degrees of susceptibility to these threats. The Amazon Basin in South America is highly vulnerable to climate change and changes in human land use. The Congo Basin in Africa experiences the same warming and drying trends as the Amazon in the Amazon, but is much more resilient. Most rainforests in Asia seem to suffer more from land use changes than climate change.
“The rainforest is perhaps the most threatened habitat on Earth: the coal-mine canary for climate change (for early warning),” said Sasan Saatchi, JPL scientist and lead author of the new study published July 23 in the journal. One Earth.
These diverse ecosystems are home to more than half of life on the planet and contain more than half of the carbon found in terrestrial vegetation. They act as a natural brake on the increase in carbon dioxide from the atmosphere due to burning fossil fuels because they “inhale” the carbon dioxide and store the carbon as they grow.
But in the last century, 15% to 20% of the rainforest was cut down and another 10% was eroded. Today’s warmer climate, which results in more frequent and widespread wildfires, has reduced the ability of forests to absorb carbon dioxide as they grow, while increasing the rate at which forests release carbon into the atmosphere as they decompose or burn.
The National Geographic Society invited a team of scientists and conservationists in 2019 to develop the new indicator. The index is based on several satellite observations and ground data from 1982 to 2018, such as the Landsat and Global Precipitation Measurement mission, covering climatic conditions, land use, and forest characteristics.
When an ecosystem can’t recover from stress as quickly or fully as it used to, it’s a sign of its weakness. The researchers linked data on stressors, such as temperature, water availability, and extent of degradation, with data on forest performance – how much biomass is living, and how much carbon dioxide they absorb. Atmosphere, the integrity of the biodiversity of the forest, and more. Correlations show how different forests have responded to stresses and how vulnerable the forests are now.
The team then used statistical modeling to extend trends over time, looking for areas of increased vulnerability and potential tipping points where rainforests will turn into dry forests or grassy plains.
Rainforest Vulnerability Index data provide scientists with the opportunity to conduct more in-depth examinations of natural processes in rainforests, such as carbon storage and productivity, changes in energy and water cycles, and changes in biodiversity. These studies will help scientists understand if there are tipping points and what they might be. The information can also assist lawmakers in planning forest conservation and restoration activities.
Written by Carol Rasmussen
Jet Propulsion Laboratory, Pasadena, California
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