Even minor changes in extreme weather could spell doom for many species

Extreme weather events can deal severe blows to wildlife and plants alike. That’s hardly news. But here’s something that might come as a surprise: even relatively minor changes in weather patterns can create havoc with ecosystems and drive species into extinction.

So say Thomas Haaland, a postdoctoral fellow at the University of Zurich in Switzerland, and Carlos Botero, an assistant professor of biology at Washington University in St Louis. For a study, published in the journal Ecology and Evolution, they devised a computer model aimed at predicting how different organisms, from bacteria to mammals, will cope with a changing climate and longer-lasting changes in their environments.

Species that breed only once in a lifetime tend to evolve “conservative” behaviors or morphologies, which better equip them to deal with environmental extremes. However, in species in which a single individual can reproduce multiple times (such as birds that nest repeatedly and on different trees in a season), evolution has favored behavior that does not take into account environmental extremes.

This means that “conservative” species can easily adapt to more frequent or widespread weather extremes but not so much when extremes become more intense. The opposite is true of species in the second “care-free” category, Haaland and Botero say. “Factors speeding up trait evolution are generally likely to hinder, rather than favor, adaptation to rare selection events,” they say. Part of the reason for that is that high mutation rates often facilitate the process of adaptation to normal conditions during intervals between environmental extremes.

“Our results challenge the idea that species that have been historically exposed to more variable environments are better suited to cope with climate change,” Botero says. “We see that simple changes in the pattern and intensity of environmental extremes could be lethal even for populations that have experienced similar events in the past. This model simply helps us better understand when and where we may have a problem.”

Climate change is expected to worsen extreme weather events both in their intensity and duration. More intense and longer-lasting heatwaves could decimate animals and plants, for instance. “Regions in which heat waves used to be rare and patchy are likely to host primarily species that do not exhibit conspicuous adaptations to extreme heat,” Botero notes.

“Our model indicates that the biggest threats of extinction in these particular locations will therefore be more frequent or widespread heat waves, and that the species of highest concern in these places will be endemics and species with small geographic distribution,” he adds. “Conversely, areas in which heat waves were historically common and widespread can be expected to host species that already exhibit adaptations for extreme heat. In this case, our model suggests that the typical inhabitants of these places are likely to be more vulnerable to hotter temperatures than to longer or more widespread heat waves.”

Computer models are approximations of reality and their accuracy can vary. “It is difficult to predict how organisms will respond to changes in extreme events because these events tend to be, by definition, quite rare,” Botero concedes. “But we can have a pretty good idea of how any given species may respond to current changes in this aspect of climate if we pay attention to its natural history and have some idea of the climatic regime it has experienced in the past.”

By understanding better how various species might respond to environmental changes, we’ll be better equipped to tailor-make conservation efforts.