Climate Change Has Been Killing Rainforest Trees For Longer Than We Realized

The lifespan of trees in the rainforests of Australia has halved in the last 35 years, and it appears to be due to the effects of climate change.

With these forests acting as significant carbon sinks, the consequences for the planet could be devastating, creating a feedback loop that is caused by global warming and contributes to it.

The signs of the increased death rate go back to the 1980s, suggesting that Earth's natural systems have responded to shifts in temperature and atmosphere for longer than we might have thought.

It was a shock to detect such a marked increase in tree mortality, let alone a trend consistent across the diversity of species and sites we studied.

Carbon stored in trees returns twice as fast to the atmosphere if there is a doubling of mortality risk.

Researchers collected more than 70,000 data points from existing records to put together the study. The team was able to track tree deaths over an extended period thanks to the earliest information.

The researchers think that global warming is to blame for the increase in tropical tree mortality.

The authors compared the stress that rainforests have experienced to what the Great Barrier Reef is going through.

The increasing drying power of the atmosphere caused by global warming may be the reason for an increase in tree death rates in tropical forests.

If that is the case, tropical forests may soon become carbon sources, and the challenge of limiting global warming well below 2 degrees C becomes more urgent.

The amount of carbon that the region is able to pull out of the atmosphere and store is being reduced by a similar increased rate of tree death. The worry is that the forests will contribute carbon to the atmosphere instead of taking it out.

The new study uses a large pool of data gathered over many years to help scientists spot long-term trends.

It is difficult to put together research projects that last decades, but more studies across a similar timescale are needed to better understand the strain that the natural world is under.

Susan Laurance, an ecologist from James Cook University in Australia, says long-term datasets like this one are very rare and important for studying forest changes in response to climate change.

This is because rainforest trees can have long lives and that tree death is not always immediate.

The research has been published.