A study, reported in February 2020, presents detailed estimates of global extinction of planet and animal species from climate change by 2070. By combining information on recent extinctions from climate change, rates of species movement and different projections of future climate, the study estimates that one in three species of plants and animals may face extinction. The results are based on data from hundreds of plant and animal species surveyed around the globe.
The study, published in the Proceedings of the National Academy of Sciences, is perhaps the first to estimate broad-scale extinction patterns from climate change by reviewing data from recent climate-related extinctions and from rates of species movements.
The study presents a bleak picture of future biodiversity on Earth, even as scientists have warned of human activities affecting species’ presence and loss.
Scientists from the Department of Ecology and Evolutionary Biology, University of Arizona, examined local extinctions that have already happened, based on studies of repeated surveys of plants and animals over time to estimate the rates of future extinctions from climate change. Data from 538 species and 581 sites around the world were studied, with the emphasis on plant and animal species that were surveyed at the same sites over time, at least a decade apart. Climate data was produced from the time of the earliest survey of each site and the more recent survey. They then concluded that around 44 per cent of the 538 species they had studied, had already gone extinct at the sites considered for the study.
The scientists have mentioned the variables that drove local extinctions and commented on how much change a population can tolerate without going extinct and how quickly populations can move to try and escape rising temperatures. This has been done by analysing the change in 19 climatic variables at each site. Based on that information, they tried to come up with detailed estimates of global extinction rates for hundreds of plant and animal species.
According to the study, maximum annual temperatures, i.e., the hottest daily highs in summer, is the key variable that best explains whether or not a population will go extinct. It found that average yearly temperatures showed smaller changes at sites with local extinction. This is even though average temperatures are largely used as a proxy for overall climate change. They said that using changes in mean annual temperatures to predict extinction from climate change could be positively misleading.
Studies before this one had emphasised dispersal, or migration to cooler habitats, as a means for species to escape from warming climates. But this study found that most species would not be able to disperse quickly enough to avoid extinction, based on their past rates of movement. Instead, they found that many species were able to tolerate some increases in maximum temperatures, though this was only up to a point. About 50 per cent of the species had local extinctions if maximum temperatures increased by more than 0.5 degrees Celsius, and 95 per cent if temperatures increase by more than 2.9 degrees Celsius.
The paper’s projections of species loss, based on how much climate would warm up in the times to come, are similar for plants and animals, but extinctions are projected to be two to four times more common in the tropics where the majority of plant and animal species occur than in temperate regions.