Ecology: The collapse of large ecosystems modelled

The collapse of large vulnerable ecosystems, such as the Amazon rainforest and Caribbean coral reefs, may only take a few decades once triggered suggests a modelling study in Nature Communications.

In ecology, regime shifts are large, persistent, and often unexpected changes in stable ecosystems, which may be driven by feedback loops once a ‘tipping point’ has been reached. The frequency of regime shifts is expected to increase as a result of climate change and environmental degradation; however, the relationship between the speed of an ecosystem’s collapse and its size is not clearly understood. This information could help identify opportunities to implement adaptive management strategies to reduce ecological damage.

John Dearing and colleagues analysed data from reports of 4 terrestrial, 25 marine and 13 freshwater ecosystem shifts and found that larger ecosystems tend to undergo regime shifts more slowly than smaller ones. However, as the size of the ecosystem increases, the additional time taken to collapse decreases, and so their collapse occurs relatively more quickly. The authors used statistical relationships backed up by computer models to estimate that an ecosystem the size of the Amazon (approximately 5.5 million km2) could collapse in approximately 49 years once initiated. For a system the size of the Caribbean coral reefs (around 20,000 km2), the time taken to collapse could be as little as a 15 year period once triggered.

The authors conclude that humanity needs to prepare for changes in ecosystems that may take place faster than previously envisaged.