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Global heating a serious threat to the world's climate refuges, study finds | Environment


Biodiversity hotspots that have given species a safe haven from changing climates for millions of years will come under threat from human-driven global heating, a new study has found.

Species that have evolved in tropical regions such Australia’s wet tropics, the Guinean forests of Western Africa and the Andes Mountains will come under increasing stress as the planet warms, the study finds.

Experts reacted to the study with shock, saying it was depressing that some of the Earth’s “most critical real-estate for saving nature” could be under threat.

Published in the journal Nature Climate Change, the study modelled global land and ocean temperatures and rainfall for the past 21,000 years.

The study then examined the impact of adding greenhouse gases to the atmosphere under two scenarios – one considered to represent very high emissions and another with much lower levels of emissions.

Places that are rich in biodiversity tend to overlap with places in the tropics that have experienced relatively stable climates in the past, providing a refuge for species when other regions have warmed, the paper explains.

Assoc Prof Damien Fordham, a global change ecologist at the University of Adelaide and a co-author of the research, told Guardian Australia this had allowed ancient species to survive, causing a “stacking” of biodiversity.

He said: “We had hoped that what we would find was that these places would continue to have stable climates. But what’s extremely worrying is that we see a shift from stable to unstable.”

He said while the study looked closely at the past 21,000 years, the areas impacted were known to have supported stable climates for millions of years.

Fordham said species in these areas tended to be adapted to survive within very narrow temperature and climate boundaries. But human-caused climate change would happen too fast for species to evolve or move, so even small shifts would have large impacts.

“Here we see really strong direct evidence of how climate change could have really adverse affects in the tropics that harbour the highest places for biodiversity on the planet.”

He said the higher and lower emissions scenarios used to project changes to the end of this century showed similar impacts.

He added: “We see this as a further reason for action on climate change, and also in considering these hotspots in our plans for climate change mitigation and adaptation.”

Global expert on conservation management Prof Hugh Possingham, of the University of Queensland and chief scientist at the Nature Conservancy, said the study was “depressing”.

He said there had been a common assumption that places that had acted as “climate refugia” of the past would carry out the same function in the future.

He told Guardian Australia: “If this is true, and they do provide compelling arguments, it is more bad news for nature.

“What I would like to see is some work on picking landscape scale actions that could ameliorate these predicted effects.

“What actions could we conceivably take that would facilitate climate adaptation at these critical locations? Habitat restoration? Reducing human pressures like hunting?”

Prof Bill Laurance, director of James Cook University’s centre for tropical environmental and sustainability science, who was not involved in the study, said it was “the scariest paper that I’ve read in the last couple of years”.

He said: “The idea that our global biodiversity hotspots – Earth’s most critical real-estate for saving nature – will be intensely vulnerable to future climate change is enough to scare the bejesus out of anyone with a lick of common sense.

“These tiny vestiges of native vegetation – essentially living arks of unique species – are going to be repeatedly body-slammed by highly fluctuating temperatures as this century progresses, according to this study. Wildfires, killer droughts, intense storms, flooding rains, the list of calamities goes on.”

But he said it was important that people did not fall into the trap of feeling helpless, adding: “This work is alarming but it’s akin to being warned that there’s a massive sinkhole in the highway ahead.

“We have a chance to dodge it if we start changing direction now.”

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