Human-caused greenhouse gases are causing the world to warm, and with this warming, stress is increasing for many plants and animals on the planet. This stress is so great that many scientists believe we are now in the middle of the “sixth extinction”; meanwhile all species are disappearing 10,000 times faster than in the industrial age. However, scientists aren’t sure which ecosystems and which species are most at risk. New research published recently Nature Climate Changeis the first study to show that a focus on risk at the species level hides wide variation in temperature tolerance even within the same species, and that this variation is greater for marine species than terrestrial species. The findings have immediate implications for management and conservation practices and offer a window of hope in an effort to adapt to a rapidly warming world.
“One of the most important biological discoveries in the past century is that evolution can happen much faster than previously thought,” says Brian Cheng, professor of marine ecology at the University of Massachusetts Amherst and the paper’s senior author. “One of the consequences of this is that different populations of the same species are more easily able to adapt to their local environment than traditional biology thought possible.”
It turns out that this rapid, localized adaptation could help ensure survival in a warming world.
Conducting a meta-analysis of 90 previously published studies in which Cheng and his co-authors collected data on 61 species, the team was able to establish a set of “upper thermal limits”—specific temperatures above which each species cannot survive. However, by zooming in further and looking at 305 different populations from this pool of 61 species, we can see that the different populations of the same marine species often had very different thermal limits. This suggests that some populations have evolved different abilities to tolerate high temperatures. The key, then, is to keep different populations of the same species interconnected so that populations adapted to higher temperatures can transfer this advantage to populations with lower thermal limits.
In other words, imagine a vast marine species such as the tiny Atlantic killifish, which ranges from the warm northern Florida coast of the United States to the cold waters of Newfoundland, Canada. Northern killifish populations may be better able to withstand warming waters if some of their southern relatives can naturally shift their range north.
“Scale matters,” says marine biologist and evolutionary ecologist Matthew Sasaki, who completed this research as part of a postdoctoral fellowship at the University of Connecticut and is the paper’s lead author. “The patterns you see across genres are not the same as what you see within genres, and the big picture story doesn’t necessarily match what’s happening at the local level.”
In yet another variation, the National Science Foundation-funded team of biologists specializing in terrestrial and marine ecosystems discovered that such intra-species variability is primarily a feature of animals that live in the ocean and tidal zones. . Populations of common terrestrial or freshwater species exhibit much greater homogeneity in their thermal limits and may therefore be more sensitive to increased temperatures. However, on land plants and animals can take advantage of microclimates to cool off and avoid temperature extremes, for example, by moving to shady places.
Taken together, the research suggests that no one-size-fits-all approach to conservation and management won’t work. Instead, the authors write, we must understand how populations adapt to their local conditions if we are to predict their vulnerability to changing conditions. A more effective approach involves ensuring that marine species can find large, undamaged habitats throughout their entire habitat so that different populations of the same species can mix and transfer adaptations that help them survive in warmer waters. And on land, we need to protect large chunks of cool ecosystems, such as old forests that terrestrial species can use as shelters.
“The glimmer of hope here,” says Cheng, “is that with conservation policies tailored to individual populations, we can give them time to adapt to a warming world.”
materials provided by University of Massachusetts Amherst. Note: Content can be edited for style and length.