0856 GMT July 22, 2018
This lower warming threshold, compared with warming of 2°C, will preserve much larger swaths of the geographic ranges of tens of thousands of land-based species of plants, vertebrates and insects living on the planet, sciencenews.org wrote.
Using a combination of climate simulations and data on the distribution of more than 115,000 terrestrial species worldwide, scientists saw distinct differences in future biodiversity depending on how much warming the planet experiences.
At 2°C of warming by 2100, 18 percent of insect species, 16 percent of plant species and eight percent of vertebrate species saw their geographic ranges shrink by more than half.
Under 1.5°C of warming, those numbers fell to six percent of insects, eight percent of plants and four percent of vertebrates, the team reported in the May 18 Science.
Study coauthor Rachel Warren, an environmental scientist at the University of East Anglia in Britain, said, “Losing half the range is a pretty big impact, because that means [the organisms] stop contributing as much to the ecosystem.”
These ecosystem contributions include air and water purification, plant pollination and nutrient cycling.
Warren said, “Until a few years ago, 2°C was the magic number. If the planet’s nations could limit global warming to just 2°C, scientists thought, the world would be relatively ‘safe’ — with little change to sea levels, species habitats or climate conditions.
“But over time, concerns began to arise that that target would still incur too great a cost.”
Many small island nations and less-developed countries, which are likely to be hit hardest by the effects of climate change, have lobbied for a more stringent reduction in greenhouse gas emissions to hold global warming to just 1.5°C by 2100.
The Paris Agreement on climate change reached in 2015 reflected that concern, as delegates agreed to limit warming to ‘well below’ 2°C.
Warren said, “But the scientific literature contained little information about the effects of a lower warming target.
“The scientific community has really been playing catch-up since the agreement.”
As part of the Paris agreement, the United Nations’ Intergovernmental Panel on Climate Change is expected in late 2018 to finalize a special report on the impacts of 1.5°C of warming.
For their study, Warren and her colleagues used species distributions from the international Global Biodiversity Information Facility database.
The inclusion of insects — a first for such a study, Warren said — is particularly important because they are at the base of many food chains and because of their contributions to ecosystems, including cycling nutrients in soils and pollinating plants.
Based on the current geographic range of each species, the team determined statistically what climatic niche each species preferred.
Then the researchers projected how climatic conditions would change globally under three warming scenarios: 1.5°C, 2°C and 3.2°C, which represents the amount of warming expected by 2100 under nations’ current pledges to limit greenhouse gas emissions.
The final step was to track the movement of those niches around the globe in response to climate change, and measure by how much they grew or shrank.
Warren said, “Overall, as the warmer the planet got, most species’ ranges got smaller. That’s for three basic reasons.”
Some climatic niches migrated right into the sea and vanished. Others crept up mountain slopes until they could go no higher. And for some species — such as many plants — the pace of climate change was too rapid for the species themselves to migrate.
So, how much of an improvement is the lower warming target?
Lauren Buckley, an ecologist from the University of Washington in Seattle, said, “It’s very much the right question to be asking.
“The study is a great first approximation of the difference in these warming scenarios.”
However, she noted, the work’s broad-brush approach means it can’t take into account some the physiology of these species or how each might respond to changing climates.
She said, “Some organisms will be winners and some losers with climate change.
“Hopefully, a lot of biologists will start to ask this question, too.”