The ultimate goal of the Paris climate agreement is to limit human-caused global warming to “well below” two-degrees Celsius, while pursuing efforts to keep it lower than 1.5 degrees. A new, large-scale study suggests that if we can keep the mercury from rising above the 1.5 mark, many of the Earth’s plants and animals—especially insects that form the base of many ecosystems—may be spared the more extreme consequences of climate change.
Prior to the adoption of the Paris agreement, most research had focused on the benefits of hitting a two degree Celsius warming target. But with the explicit inclusion of an aspirational 1.5 degree warming limit in the agreement’s text, the scientific community has spent the last two years studying the additional benefits of that more ambitious target.
Additional research now shows vast differences in the climatic consequences of restricting warming to 1.5 versus two degrees. But impacts on plants and animals still weren’t well-understood. That’s where a team from the University of East Anglia and James Cook University in Australia came in, illustrating just how important that half a degree is for literally tens of thousands of species.
The team used data from the Global Biodiversity Information Facility (GBIF), which contains observational records of precise geographical locations for over 200,000 species. After filtering for species with particularly good records, they were left with about 115,000 species, including 71,000 plants, and 31,000 insects, making this the largest scale study of its kind.
The team then looked at the climatic characteristics in each of the observed locations, generating a statistical relationship between climate and species presence. This gave them a model that could predict whether or not a species would live somewhere based on climate information. Rachel Warren, professor of global change and environmental biology at the University of East Anglia and lead author on the study, describes this predicted zone of habitability as a “shadow on the surface of the Earth.”
“As the climate changes, you can see this shadow moving,” Warren told Earther. “In the Northern Hemisphere, it will move slowly towards the North Pole, or if it’s in a valley, it will move up a mountain range.”
This moving “shadow” is produced by taking the climate-based location prediction model, and applying it to twenty one different future climate scenarios, with differing levels of warming by the year 2100.
The team’s results, published today in the journal Science, show that the impacts of 1.5 and two degrees Celsius are worlds apart.
By restraining warming to 1.5 degrees instead of two, overall, the number of species that are predicted to suffer more than 50 percent range loss is reduced by about half.
Insects, it seems, are particularly sensitive to warming. If current emissions pledges are met (resulting in an estimated 3.2 degree Celsius rise), half of all insect species are projected to lose half their range. At two degrees, that proportion is 18 percent, and at 1.5 degrees, it’s only six percent.
“There are very large ecological benefits from limiting warming to 1.5 degrees Celsius because of the protection of insects, which are at the bottom of the food chain,” Warren told Earther.
It’s very likely that these stark results are actually conservative, since the models don’t account for species interactions that might be impacted by climate change.
Land use change and resource overexploitation are also key factors in range loss, notes Alejandra Morán-Ordóñez, a landscape ecologist at the Forest Sciences Centre of Catalonia, who was not involved in this study. Neither are incorporated into climate-based models (like in Warren’s study or in general), which means that the dire predictions surrounding two and 3.2 degrees of warming are likely only capturing a portion of the full consequences.
The immense benefit to insects in keeping temperature rise at 1.5 degrees is a crucial message for humans. Among insects, the risks for crop pollinator species like bees and flies are greatly reduced at 1.5 degrees. This benefit could prove critical, says Warren, since it appears as though insect populations may already be experiencing a significant global decline. Last year, a study showing that populations of insects in Germany had mysteriously plunged by three-quarters in three decades provided a new source of anxiety about the future state of Earth’s ecosystems. But it appeared climate change had contributed little to this drop.
“The concern, then,” Warren said, “is that the findings we have is on top of what has already been observed.”
For Morán-Ordóñez, highlighting the ecological significance insects is a major strength of the study.
“I think we generally underestimate the role that these little creatures play in our lives,” she said. “It is important to raise awareness of this importance and the potential consequences of their loss.”