Not so fast: Modeling shows ecosystems can survive environmental change—up to a point
A Skoltech researcher and her colleagues from Canada and Chile experimented with mathematical evolutionary models to explore how well ecosystems can keep up with changing environmental conditions—a question all too relevant in our current ecological situation. They found that the speed of this change ultimately holds the key to species survival, so just slowing down climate change, habitat degradation and other similar processes can already lead to better outcomes for the ecosystems. The paper was published in the journal Ecology and Evolution.
The expansion of human civilization and its increasing pressure on ecosystems, primarily through global climate change and destruction of natural habitat, may likely drive many species to the brink of extinction. But the extent to which wildlife can adapt to this pressure, as well as any potential limits to the resilience of ecosystems, remain a widely discussed topic.
"An ability to survive under changing conditions is a key feature of all living creatures, it includes both an extension of habitat area and adaptation to changes in the environment. As a result, we are surrounded by such an amount of biodiversity. An adaptation to changing environment is occurring not only over long time periods producing important macroevolutionary events such as massive species diversifications or extinctions, it is also a formation of new traits in already existing populations—adaptation to rising ocean temperature that prevents coral bleaching or development of antibiotic or drug resistance—which can be fast enough," says Iaroslav Ispolatov from Universidad de Santiago de Chile (USACH), a coauthor of the paper.
He notes that, to choose the best strategy to deal with these ecological or medical problems, we need to better understand the mechanisms behind adaptation. Since studying evolutionary processes on a laboratory timescale is quite hard, numerous theoretical studies, based on models and various scenarios, have pointed, among other things, to factors that can increase or decrease the likelihood of survival under changing conditions. In their new paper, Skoltech Ph.D. student and first author Evgeniia Alekseeva and her colleagues decided to focus on the rate of this change, given that recently a lot of the crucial environmental variables have been moving at an unprecedented pace.
Researchers performed their simulations, based on the logistic competition model (a class of models where competition from similar individuals limits population growth). They ran simulations where abiotic, that is, external parameters would change at various rates over time, and observed the outcomes, such as existing species expanding, new species forming, or life in the model going extinct.
Alekseeva and her coauthors concluded that, while generally any adverse environmental changes cause a reduction in the number of species, in total population size, and in phenotypic diversity, the most important factor determining the outcome is indeed the rate of this change. In other words, there seem to be certain "tipping points," or thresholds, in terms of how fast the conditions can move, beyond which none of the species in the model would survive.
"We wanted to find critical factors which affect the survival of the community in the most dramatic way. We found that ecological stress on the community may vary depending on its features and some ecological systems are now at a greater risk of extinction than others. Systems with high-organized species turn out to be the most vulnerable ones, and some of them have indeed already suffered due to climate change. This seems to be true, for example, for Arctic ecosystems with their beautiful and unique mammals, such as polar bears and foxes, seals, beluga whales and others, whose survival is already of great concern," Alekseeva says.
However, the main conclusion of their theoretical study, per Alekseeva, is "that the range of rates of environmental change, when only some communities suffer and many others are able to adapt, is relatively narrow, and above a certain rate many communities will dramatically decrease their diversity or go fully extinct."
"Thus, since the current rate of environmental change increases each year, the problem is not limited by few suffering ecosystems, but is absolutely global," she says.