With the world's humid tropical forests under threat due to changing land use and climate change, scientists have created a new technique to monitor which are at most risk.
A new "tropical forest vulnerability index" (TFVI) could help researchers to monitor forests via satellite data – allowing researchers to focus their efforts on the most-threatened areas.
Tropical rainforests are hovering on the edge of a deadly "tipping point", Nasa experts believe.
Sassan Saatchi of Nasa's Jet Propulsion Laboratory said: "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.
"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 policymakers plan for conservation and restoration of these forests."
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Saatchi and his colleagues set out to develop a unique vulnerability index that could work across all rainforests based on observations of climate and vegetation from satellites.
The new index combines numerous measurements and indicators of forest ecological functions and services, including carbon and water fluxes and biodiversity.
It also allows researchers to identify and monitor areas with increasing vulnerability or potential threats before it's too late.
Their studies have shown that different regions of the tropics are responding differently to climate threats, with some regions showing more apparent resilience than others.
For instance, forests in the Americas appear to be more vulnerable to stresses than those in Africa, where they are showing relative resilience to changing climate.
In Asia, tropical forests appear more vulnerable to land use and fragmentation.
Saatchi said: "The findings show that the vulnerability of rainforests is much larger than predicted in the past, and areas that are disturbed or fragmented have almost no resilience to climate warming and droughts.”
"In addition, the results of our study suggest that rainforests are losing their capacity to cycle carbon and water as before. This is occurring gradually at the continental scale and more rapidly at the regional scale, with significant implications for the global carbon sink and climate."
The TFVI was developed by many scientists and conservationists assembled by the National Geographic Society and Rolex and therefore represents a consensus approach from the broader community, Saatchi notes.
The hope is that a larger global community of scientists and policymakers, particularly in tropical countries, will now make use of the index to systematically assess the vulnerability of rainforest resources.
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