Right now, we are on track to be living in a world that is, on average, 3.2°C warmer than pre-industrial levels by 2100. That would lead to widespread devastation for human civilization, brought about in the form of things like drought, floods, extreme storms, and sea-level rise.
But for the majority of animals and plants, 3.2°C of warming would mean having most of their habitat wiped out entirely. In a paper published today (May 16) in the journal Science, researchers at the University of East Anglia in Norfolk, UK, and James Cook University in Australia looked at how the projected temperature rise would impact 31,000 insect species, 8,000 bird species, 1,700 mammal species, 1,800 reptile species, 1,000 amphibian species, and 71,000 species of plants.
They found that 3.2°C of warming would cause half of all insect species to lose 50% or more of their geographical ranges, which would be a devastating blow to those species and to everything that relies on them. Bees are a classic example: If a bee species important to pollinating specific crops lost 50% of their range, for example, those crops would also perish across half of the land where that species of bee normally roams.
Meanwhile, 26% of all species of mammals, birds, reptiles, amphibians, and fish as well as 44% of plants would lose more than half their geographic ranges in a 3.2°C-warmer world.
The good news is that most of the world agrees a 3.2°C rise in temperature would be unacceptable. Most countries are attempting to make changes designed to limit warming to 2°C above pre-industrial levels. If the world manages that, it would mean a saving the majority of the species from the threats connected to climate change. In a 2°C-warmer world 18% of insects, 16% of plants, and 8% of mammals, birds, reptiles, amphibians, and fish would lose more than 50% of their range by 2100, the researchers found.
Of course, losing less than half of your habitat isn’t great either, but at least in this scenario, far more species would stand a chance.
The researchers argue that the world should be trying to track towards 1.5°C of warming instead of 2°C. In a 1.5°C scenario, 6% of insects, 8% of plants, and 4% of mammals, birds, reptiles, amphibians, and fish would lose more than half their habitat range.
That means limiting warming to 1.5°C as compared with 2°C would cut the risks that climate change poses to invertebrate animals and plant species’ ranges by half. For insects, keeping to 1.5°C cuts the risks by two-thirds. A half-degree makes all the difference.