‘Sensing system’ spots struggling ecosystems

A new “resilience detection system” can identify ecosystems at risk of collapse, research shows. The system uses satellites to spot problem areas — including those at risk of “tipping points” — and can also measure the success of conservation and restoration efforts.

Resilient ecosystems have a greater capacity to absorb shocks such as droughts, fires and floods, so a decrease in resilience makes an ecosystem more vulnerable. The research team, led by the Global Systems Institute (GSI) at the University of Exeter, has developed a prototype detection system. Early results indicate that global average resilience has declined over the past 20 years.

“By identifying regions that are losing resilience, this system shows us which places we should be most concerned about,” said GSI Director Professor Tim Lenton. “It could raise a red flag and lead to action to restore resilience.”

“This is especially important in places with a tipping point (a threshold that causes irreversible change), such as the Amazon rainforest.”

A recent study by the GSI team showed that the Amazon rainforest is losing resilience — a situation “consistent” with an approaching tipping point that could lead to dieback and turn much of the forest into savanna.

The new paper draws on regular measurements of the Normalized Difference Vegetation Index (NDVI) to see how ecosystems respond to changing conditions.

The results, based on 20 years of NDVI data, include:

“Pronounced” loss of resilience in the Eastern Mediterranean, Central America and the Caatinga (northeast Brazil), all of which have suffered from prolonged drought.
The strongest trends of declining resilience occur in tropical and subtropical dry broadleaf forests, mountain grasslands and scrubland.
The study “zoomed” in South and East Asia, picking out sample regions where resilience has been lost: dry deciduous forests in India, coniferous forests in China and a “large portion” of Mongolian steppe grasslands.

Professor Lenton said the measurement system can measure the effectiveness of projects such as TIST, which has seen thousands of farmers plant and protect millions of trees in four countries. “You can see if these projects are returning resilience to an ecosystem,” he said.

The system now needs to be developed further, and Professor Lenton said incorporating marine ecosystems (not just those on land) would be a big step forward.

The article was published in the magazine Philosophical Transactions of the Royal Society B.