Global warming is on track to cause a major wipeout of insects, compounding already severe losses, according to a new analysis.
Insects are vital to most ecosystems and a widespread collapse would cause extremely far-reaching disruption to life on Earth, the scientists warn. Their research shows that, even with all the carbon cuts already pledged by nations so far, climate change would make almost half of insect habitat unsuitable by the end of the century, with pollinators like bees particularly affected.
However, if climate change could be limited to a temperature rise of 1.5C - the very ambitious goal included in the global Paris agreement - the losses of insects are far lower.
The new research is the most comprehensive to date, analysing the impact of different levels of climate change on the ranges of 115,000 species. It found plants are also heavily affected but that mammals and birds, which can more easily migrate as climate changes, suffered less.
“We showed insects are the most sensitive group,” said Prof Rachel Warren, at the University of East Anglia, who led the new work. “They are important because ecosystems cannot function without insects. They play an absolutely critical role in the food chain.”
“The disruption to our ecosystems if we were to lose that high proportion of our insects would be extremely far-reaching and widespread,” she said. “People should be concerned - humans depend on ecosystems functioning.” Pollination, fertile soils, clean water and more all depend on healthy ecosystems, Warren said.
In October, scientists warned of “ecological Armageddon” after discovering that the number of flying insects had plunged by three-quarters in the past 25 years in Germany and very likely elsewhere.
“We know that many insects are in rapid decline due to factors such as habitat loss and intensive farming methods,” said Prof Dave Goulson, at the University of Sussex, UK, and not part of the new analysis. “This new study shows that, in the future, these declines would be hugely accelerated by the impacts of climate change, under realistic climate projections. When we add in all the other adverse factors affecting wildlife, all likely to increase as the human population grows, the future for biodiversity on planet Earth looks bleak.”
In the new analysis, published in the journal Science, the researchers gathered data on the geographic ranges and current climate conditions of 31,000 insect species, 8,000 birds, 1,700 mammals, 1,800 reptiles, 1,000 amphibians and 71,000 plants.
They then calculated how the ranges change when global warming means some regions can no longer support particular species. For the first time in this type of study, they included the 1.5C Paris target, as well as 2C, the longstanding international target, and 3.2C, which is the rise the world will experience by 2100 unless action is taken beyond that already pledged.
The researchers measured the results in two ways. First, they counted the number of species that lose more than half their range and this was 49 percent of insect species at 3.2C, falling to 18 percent at 2C and 6 percent at 1.5C. Second, they combined the losses for each species group into a type of average measure.
“If you are a typical insect, you would be likely to lose 43 percent of your range at 3.2C,” Warren said. “We also found that the three major groups of insects responsible for pollination are particularly sensitive to warming.”
Guy Midgley, at University of Stellenbosch, South Africa and not part of the research team, said the new work built on previous studies but is far more comprehensive. He said major impacts on wildlife would be expected given the potential scale of climate change: “Global average surface temperatures in the past two million years have rarely approached the levels projected over the next few decades.”
Warren said the new work had taken account of the ability of species to migrate, but had not been able to include the impact of lost interactions between species as ranges contract, or of the impacts of more extreme weather events on wildlife. As both of those would increase the losses of range, Warren said the estimates of losses made were likely to be underestimates.
Warren said that the world’s nations were aware that more action on climate change is needed: “The question is to what extent greater reductions can be made and on what timescale. That is a decision society has to make.”
Another study published in Science on Thursday found that one third of the world’s protected areas, which cover 15 percent of all land, are now highly degraded by intense human pressure including road building, grazing, and urbanisation.
Kendall Jones, at the University of Queensland, Australia, who led the work, said: “A well-run protected area network is essential in saving species. If we allow our protected area network to be degraded there is a no doubt biodiversity losses will be exacerbated.”