Nightmare Study Says A Third Of Animals Could Go Extinct In The Next 50 Years
Some of the world's most stunning plants and animals could simply disappear according to mind-boggling projections that up to half the natural world might become extinct by 2070.
Rapidly-rising temperatures are heating the world faster than animals and plants can adapt, a startling university study from the University of Arizona has laid out.
The paper -- published in the Proceedings of the National Academy of Sciences journal -- is thought to be the first to estimate global extinction projections based on current trends already occurring.
"If humans cause larger temperature increases, we could lose more than a third or even half of all animal and plant species," said author John J. Wiens, of the university's Department of Ecology and Evolutionary Biology.
"In a way, it's a 'choose your own adventure'."
The global Paris Agreement on climate aims to limit average global temperature rises to below 1.5 degrees. Wiens said even if that happens, the Earth could still lose up to 20 percent of plant and animal species by 2070 -- but if temperatures rise by three degrees, which is predicted under current emissions trends, then the extinction numbers could be far greater.
Australia already has an ignominious climate extinction honour, being the (former) home of what is recognised as the first mammal to be wiped out by climate change. The Bramble Cay melomys, a small brown rat, disappeared from its native habitat on an island off the Great Barrier Reef, with rising sea levels blamed.
The Arizona researchers came to their frightening findings by looking at data around recent climate-related extinctions which have already occurred, rates of species movement, adaptation and resilience of more than 500 plant and animal species. and climate change modelling.
By looking at a set of 538 species from 581 locations across the globe, the researchers modelled how organisms had already been affected by climate change over the past 10 years, such as whether they adapted, changed or moved to different areas -- finding that "44 percent of the 538 species had already gone extinct at one or more sites".
"When we put all of these pieces of information together for each species, we can come up with detailed estimates of global extinction rates for hundreds of plant and animal species," co-author Cristian Román-Palacios said.
The biggest factor in climate-related extinction, the researchers found, was the maximum annual temperature, or the hottest temperatures in summer.
Previous studies showed some species could 'disperse' or move to more favourable locations to escape the changing conditions, but that climate was actually changing too quickly for the plants and animals to adapt or move.
"They found that about 50 percent of the species had local extinctions if maximum temperatures increased by more than 0.5 degrees Celsius, and 95 percent if temperatures increase by more than 2.9 degrees Celsius," the University of Arizona said of the research.
Last November, the United Nations reported that even if all Paris Agreements commitments are met, the world will still likely see a 3.2 degree rise in temperatures -- which the U.N. warned would have "even wider-ranging and more destructive climate impacts", including mass extinctions and making huge swathes of the planet "uninhabitable".
While the Arizona study said species worldwide would be affected, it would be those living in the tropics of the globe -- home to some of the most beautiful and stunning animals and plants -- which would be the hardest-hit.
Extinctions would be two to four times more common in the tropics than in temperate areas, the researchers said.
"This is a big problem, because the majority of plant and animal species occur in the tropics," Román-Palacios said.
Animals already in danger from climate change -- including risks around loss of habitat, loss of food or susceptibility to temperature changes -- include polar bears, green sea turtles, monarch butterflies, cheetahs and African elephants, according to the World Wildlife Fund.
Animals such as polar bears are considered 'habitat specialists', with the WWF saying they "rely almost entirely on the sea-ice environment", so changing ice levels or sea temperatures are feared to impinge on their resilience.
Green sea turtles are "very sensitive" to temperature changes in the oceans, with the gender of baby turtles determined by the temperature of the sand they are laid in.
Frogs, penguins and sea coral are also among those considered vulnerable to temperature-related climate risks.