It has long been thought that species previously exposed to more variable weather and climate conditions are more likely to survive extreme events. However, this study challenges that assumption.
“It is difficult to predict how organisms will respond to changes in extreme events because these events tend to be, by definition, quire rare,” said study lead author Professor Carlos Botero of Washington University in St. Louis. “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 climactic regime it has experienced in the past.”
Botero worked with his former student, Thomas Haaland, now a postdoc at the University of Zurich in Switzerland, to develop an evolutionary model of how populations respond to rare environmental extremes—for example, 500-year floods. These events can obviously be tricky for evolution because it’s hard to adapt to hazards that are almost never encountered.
Through computer simulations, Haaland and Botero found certain traits and experiences emerged as key indicators of vulnerability—and you might be surprised at the results.
It turns out that species that breed a single time in their lifetime tend to evolve conservative behaviors or morphologies, as if they were expecting to experience extreme climate events or other environmental extremes every time.
However, species in which a single individual can reproduce multiple times and in different contexts (for example, birds or cats), evolution favors behaving as if those extremes just never happen.
What that means is that species belonging to the “conservative” category are actually more easily able to adapt to more frequent or widespread extremes, but they have trouble adjusting when those extremes become more intense. For the “care-free” category of species, the opposite is true.
Furthermore, the researchers found that factors speeding up trait evolution are more likely to hinder, rather than favor, adaptation to what they refer to as rare selection events. High mutation rates facilitate the process of adapting to normal conditions during the long intervals between extreme climate or environmental events.
“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 said. “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.”
The model gives conservation organizations and wildlife professionals some insight into different species’ vulnerability to extreme climate events based on assessments of their natural histories and historical environments.