Climate change could wipe out one-third of all the plant and animal species on Earth within half a century, scientists have warned.
In a new study, University of Arizona researchers analysed data on recent extinctions and compared it against weather predictions for the next 50 years.
Cristian Román-Palacios and John J. Wiens from the university’s department of ecology and evolutionary biology surveyed data from 538 species and 581 sites around the world.
They found that 44% of the 538 species had already gone extinct at one or more sites – which is known as local extinction.
‘By analyzing the change in 19 climatic variables at each site, we could determine which variables drive local extinctions and how much change a population can tolerate without going extinct,’ Román-Palacios said.
‘We also estimated how quickly populations can move to try and escape rising temperatures. 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.’
The study identified maximum annual temperatures – the hottest daily highs in summer – as the key piece of information that ‘best explains whether a population will go extinct’.
Researchers found that many species were able to tolerate some increases in maximum temperatures, but only up to a point.
They found that about half of the species experienced local extinctions if maximum temperatures increased by more than 0.5 degrees Celsius – but a 95% extinction rate if temperatures increase by more than 2.9 degrees Celsius.
The academics said that ‘projections of species loss depend on how much climate will warm in the future’.
‘In a way, it’s a “choose your own adventure,”‘ Wiens said.
‘If we stick to the Paris Agreement to combat climate change, we may lose fewer than two out of every 10 plant and animal species on Earth by 2070.
‘But if humans cause larger temperature increases, we could lose more than a third or even half of all animal and plant species, based on our results.”
The paper’s projections of species loss are similar for plants and animals, but extinctions are projected to be two to four times more common in the tropics than in temperate regions.
‘This is a big problem, because the majority of plant and animal species occur in the tropics,’ Román-Palacios added.
Humanity is about to reach the climate change ‘point of no return’ and our attempts to save the planet have been ‘utterly inadequate’, UN Secretary-General Antonio Guterres warned last year.
Speaking before the start of a two-week international climate conference in Madrid, the UN chief said rising temperatures are already causing chaos around the world.
He suggested the world has the scientific knowledge and the technical ability to tackle global warming, but ‘what is lacking is political will.’
‘The point of no return is no longer over the horizon,’ Guterres told reporters in the Spanish capital.
‘It is in sight and hurtling toward us.’
Guterres said there was mounting scientific evidence showing the impact man-made emissions of greenhouse gases are already having on the planet, including record temperatures and melting polar ice.
But he insisted that his message was ‘one of hope, not of despair’.
He added: ‘Our war against nature must stop and we know that that is possible.’
‘What is still lacking is political will,’ he added.
‘Political will to put a price on carbon. Political will to stop subsidies on fossil fuels. Political will to stop building coal power plants from 2020 onwards. Political will to shift taxation from income to carbon. Taxing pollution instead of people.’
The warning came after scientists said nine climate change ‘tipping points’ have now been crossed and the ‘cascade of changes’ could spell doom for humanity.
They called for the establishment of a ‘state of planetary emergency’ and urged governments to take urgent action to stop the production of greenhouse gases and said global warming risked creating a ‘hothouse Earth’ that ‘could threaten the existence of human civilisations’.
‘A decade ago we identified a suite of potential tipping points in the Earth system, now we see evidence that over half of them have been activated,’ said Professor Tim Lenton, director of the Global Systems Institute at the University of Exeter and lead author of a new paper in the respected journal Nature.
‘The growing threat of rapid, irreversible changes means it is no longer responsible to wait and see. The situation is urgent and we need an emergency response.
‘We might already have crossed the threshold for a cascade of inter-related tipping points.
‘However, the rate at which they progress, and therefore the risk they pose, can be reduced by cutting our emissions.’
Countdown to doomsday: If these nine natural
The collapse of major ice sheets on Greenland, West Antarctica and part of East Antarctica would cause roughly 10 metres of irreversible sea-level rise.
If rainforests, permafrost and boreal forests die off, huge amounts of greenhouse gases will be released into the air and amplify global warming.
We could stave off this disaster by reducing emissions, but this would only ‘allow more time for low-lying populations to move’ to another part of the world.
And once we’ve reached several tipping points, a cataclysmic ‘cascade’ could begin which accelerates climate change to terrifying proportions.
‘If damaging tipping cascades can occur and a global tipping cannot be ruled out, then this is an existential threat to civilization,’ the scientists wrote.
‘No amount of economic cost-benefit analysis is going to help us. We need to change our approach to the climate problem.’
Co-author Johan Rockström, director of the Potsdam Institute for Climate Impact Research, said: ‘It is not only human pressures on Earth that continue rising to unprecedented levels.
‘It is also that as science advances, we must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming.
‘This is what we now start seeing, already at 1°C global warming.
‘Scientifically, this provides strong evidence for declaring a state of planetary emergency, to unleash world action that accelerates the path towards a world that can continue evolving on a stable planet.’
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