Tropical Rainforest Vulnerability Index May Help Conserve Them

The goal is for it to provide an early warning for areas under the greatest threat.

Amazon rainforest

Ignacio Palacios/Getty Images

Humid tropical forests are under huge threat from rising temperatures and changes to land use. Most of us are now well aware of the vulnerability of these crucial ecosystems. And there are worrying signs which suggest that these ecosystems could reach tipping points–potentially points of no return. 

But there is some good news. Researchers have come up with a new Vulnerability Index that could help keep tabs on these forests which could be very important in helping to avoid "tipping points" and in their conservation. 

Researchers reporting in the July issue of journal One Earth, in a paper entitled "Detecting vulnerability of humid tropical forests to multiple stressors," have built a spatially explicit tropical forest vulnerability index (TFVI). The scientists and conservationists involved in this work were assembled by the National Geographic Society and Rolex. 

This index is designed to identify areas where rainforests are losing resilience and may be changing towards an irreversible tipping point. It can serve as a monitoring system for tropical forests and provide early warning signs which can be used to inform best practices in the region when it comes to conservation, increasing resilience, and mitigating the effects of climate change. 

"Frequent droughts, higher temperature, and longer dry seasons, along with increasing pressures from deforestation and degradation in the last two decades, have pushed the tropical rainforests to the verge of a tipping point," said Sassan Saatchi of NASA's Jet Propulsion Laboratory in a statement. "What we predicted using climate models a decade ago, we are observing on the ground. Now is the time to do something and not later. This work takes advantage of a suite of satellite observations made for the past few decades to show how and where the tipping points may be reached and to help policy makers plan for conservation and restoration of these forests."

Deforestation and Degradation of Tropical Rainforests

We all know that tropical forests play a crucial and dominant role in the planet's natural cycles. But deforestation and degradation of these vital ecosystems continue apace. These forests are under increasing threat from the agricultural spread and other human activity and are also under immense stress due to our changing climate. Since the early 1990s, between 15% and 20% of humid tropical forests have been cleared and at least an additional 10% have been degraded. 

However, the vulnerability and stresses on tropical forests vary considerably depending on their geographical location, and over time. The levels of stress which forests can tolerate before they face a tipping point are poorly understood. This paper highlights that climate change and land-use pressures have slowed the recovery ate of forest carbon cycling. 

The findings of this study show that the vulnerability of rainforests is much worse than previously predicted. And it is clear that areas of greatest disturbance or fragmentation have the least resilience, often none at all, to climate warming and droughts.

If climate change and land-use activities continue to escalate as projected, the forests may even become a source of carbon to the atmosphere. Widespread tree deaths or transition to drier, savanna-like woodlands could devastate the wildlife of these regions and, of course, exacerbate climate change since these humid tropical rainforests would no longer be providing their carbon sequestration services. While some shifts will likely happen gradually, researchers warn that some forests, particularly the Amazon, could transform far more rapidly. 

The Tropical Forest Vulnerability Index

To create their new vulnerability index (TFVI), researchers utilized satellites and other models and measurements to track land temperature, above-ground photosynthesis and production, and shifts in biodiversity and species abundance. They also looked at the loss of tree cover from deforestation and fire. And noted changes in carbon and water transfer between plants and the atmosphere. The scientists took advantage of a body of knowledge from satellite observations made for the past few decades. 

Researchers have applied their vulnerability index to forests in different areas of the globe. And have noted that forests in the Americas exhibit extensive vulnerability to the stresses involved. While those in Africa show relative resilience in the face of climate change, and those in Asia reveal more vulnerability to land use and fragmentation. 

The Amazon is most at risk. Widespread deforestation in the region, along with a rapidly changing climate, are notably impacting ecosystem function across a number of metrics. Deforestation continues to rise. Fast-growing drought-tolerant trees are now outcompeting species that do best in wet conditions. When rains come, they come hard, causing flooding. But drought periods are increasingly common and serious. Wildfires are burning more wildly. And trees are dying at unprecedented rates. A tipping point could be on the horizon–if it is not already too late. 

By putting together all the data and metrics for the first time, scientists have painted a worrying picture for the Amazon and elsewhere. But it is not too late for humanity to change course. This new vulnerability index helps us see things very starkly and clearly. It can also help monitor future changes and make sure that the right resources are directed in the right ways to halt catastrophe and aid in the recovery of tropical forests. 

View Article Sources
  1. Saatchi, Sassan, et al. "Detecting Vulnerability of Humid Tropical Forests to Multiple Stressors." One Earth, vol. 4, no. 7, 2021, pp. 988-1003., doi:10.1016/j.oneear.2021.06.002

  2. Vancutsem, C., et al. "Long-Term (1990–2019) Monitoring Of Forest Cover Changes In The Humid Tropics." Science Advances, vol. 7, no. 10, 2021, p. eabe1603., doi:10.1126/sciadv.abe1603