Do Climate Models Underestimate Extinctions?
“We have really sophisticated meteorological models for predicting climate change,” says ecologist Mark Urban, the lead author of a study that looks at whether the current climate models properly understand species competition and movement and, therefore, the impact the future climate will have on animals.
“But in real life, animals move around, they compete, they parasitize each other, and they eat each other. The majority of our predictions don’t include these important interactions.”
Urban, who is assistant professor of ecology and evolutionary biology at the University of Connecticut, notes that while there have been plenty of studies that have shown species moving in response to climate change, often looking for higher altitudes where temperatures are cooler in which to survive, the models do not always recognise the fact that some species simply cannot disperse fast enough. Additionally, even if a species of animal or plant can disperse fast enough, they may be outcompeted by the species that already live in those higher altitudes, or those that have beaten them to it.
“When a species has a small range, it’s more likely to be outcompeted by others,” Urban says. “It’s not about how fast you can move, but how fast you move relative to your competitors.”
The Bad News
Along with coauthors Josh Tewksbury and Kimberly Sheldon of the University of Washington, Urban created a mathematical model that takes into account the varying rates of migration and the the different intensities of competition seen in ecological communities. Their goal was to put themselves in a position to predict the success of migration to completely new habitats.
Unsurprisingly, their model showed that flora and fauna with the ability to adjust to climate change will have a competitive advantage over those species unable to, leaving animals with small geographic ranges, specific habitat needs, and difficulty dispersing to go extinct.
Urban likens this scenario to a train traveling up a mountain on a track. If each boxcar – representing a species – travels at the same speed, they will likely all reach the top eventually. But, in reality, each car can move at a different speed, creating a collision course.
“There’s always a car in front of you and a car behind,” explains Urban. “When you introduce the ability to move at different speeds, they’re constantly bumping into one another, even running each other over. It’s a recipe for disaster.”
The Really Bad News
The bad news out of this, and yes it’s still to come, is that the authors of the paper, published in the January 4th online edition of the journal Proceedings of the Royal Society B: Biological Sciences, believe that the current predictions of biodiversity loss as a result of climate change could be vastly underestimating species extinction. The authors note that tropical communities could be among the hardest hit in a changing climate, due in part to the fact that many species often live within a very confined location.
Urban says this is a first step toward making climate change predictions of biodiversity more sophisticated.
“This is a first step – to include in our models things that we know are true, like competition and dispersal,” says Urban. “Knowing these things, can we predict which species might be most at risk?”