Climate change is threatening the survival of plants and animals around the globe as temperatures rise and habitats change.
Some species have been able to meet the challenge with rapid evolutionary adaptation and other changes in behavior or physiology. The dark dragonflies are getting brighter to reduce the amount of heat they absorb from the sun. Mustard plants are flowering earlier to take advantage of earlier snowmelt. Lizards are becoming colder to handle the great diversity of our new climate.
However, scientific studies show that climate change is happening much faster than species are changing.
What is an evolutionary adaptation?
Climate scientists use the word “adaptation” in many ways, but it has a very specific meaning for biologists: It refers to genetic changes that are passed down from generation to generation and improve a species’ ability to survive in its environment. .
These genetic modifications make evolutionary adaptation different from “acclimatization” or “acclimatization,” which involves advantages that are not passed on to offspring. For example, when people move to high altitude cities, they start producing more red blood cells as they get used to the low oxygen.
Around the world, plants and animals have adapted to many different hot and dry habitats, prompting scientists to question whether species might also adapt to our rapidly changing climate, too.
So far, the answer seems to be no for most species.
Developing, fast and slow
A recent study of populations of 19 species of birds and mammals, including owls and deer, points to one potential barrier to adaptation.
In animals that take several years to reach breeding age, the climate has already changed by the time their offspring are born. The genes that gave the parents an advantage – such as hatching at the right time or growing to optimal size – are no longer as beneficial to the offspring.
Populations of these slowly maturing animals are adapting to climate change, but not enough during each generation to thrive in the changing conditions. In fact, the rate of evolution is so different from the rate of global warming that the authors of the study estimate that almost 70% of the local populations they studied are already at risk of extinction due to climate in the coming years.
Small-bodied animals, such as many fish, insects and plankton, tend to mature quickly. However, recent research on small fish and a fast-maturing type of plankton called copepods has revealed another barrier to rapid genetic adaptation to climate change.
Many species have genes that allow them to survive in environments that are 1 to 2 degrees Celsius (about 2 to 4 Fahrenheit) warmer than today, but new genetic mutations must emerge to survive if climates reach 4 to 5 C (about 7 to 9). F) warmer, and possible in some regions, especially if greenhouse gas emissions continue at a high rate.
To test the resilience of species, the scientists warmed to populations of these rapidly maturing species over the next few generations to observe their genetic changes. They found that both copepods and small fish were able to adapt to the first few warming stages, but populations soon became extinct beyond that. This happened because genetic mutations that increased their ability to survive in warmer conditions occurred at a slower rate than the temperatures rose.
Cold-blooded species, such as lizards, frogs and fish, are particularly vulnerable to climate change because their ability to regulate their own body temperature is limited. Their ability to evolve in response to climate change is expected to be critical to their survival.
However, rapid adaptation to climate change often comes at a cost: populations become smaller due to the deaths of individuals unable to tolerate new, warmer temperatures. Therefore, even if species evolve to survive climate change, their smaller populations may become extinct due to problems such as inbreeding, new harmful mutations or bad luck, such as disease epidemics.
In a now-classic study, researchers studying lizards in Mexico found that the high death rates of heat-sensitive individuals—which represent only a subset of the total population—caused 12% of lizard populations in Mexico went extinct between 1975 and 2009. Even with some adult refractory lizards surviving in each population under the warmer conditions, the researchers estimated that climate change would kill so many heat-sensitive adults within each population that -54% of all populations would disappear by 2080.
Evolutionary adaptation is not just a species choice
Another way in which species adapt to elevated temperatures is through adaptation, sometimes called “phenotypic plasticity”. For example, great tits in the UK – small birds common in yards and forests – lay their eggs earlier in warmer years so that their nests hatch just as the winter weather ends, no matter when that happens.
However, a recent analysis of more than 100 species of beetles, grasshoppers and other insects around the world found that acclimation may not help those species enough. The study authors found that the species they reviewed gained an average of only 0.1 C (about 0.2 F) more heat tolerance when adapting to 1 C (about 2 F) warmer air temperatures with during their development. Thus, it appears that the rate of global warming is outpacing the ability of species to adapt, too.
Plants and animals could escape the effects of global warming by moving to cooler habitats. A global analysis of more than 12,000 different species of plants and animals recently showed that many species are migrating to the poles fast enough to keep up with rising temperatures, and that many tropical species are moving up the slope to higher altitudes as well.
However, migration has its limits. Research shows that tropical birds that already live high in the mountains may be lost because there is no room for them to migrate further up. Tropical species, therefore, could be what the authors call a “stairway to extinction”.
High latitude and high altitude habitats also present many challenges for species to overcome other than temperature. Our own research on 800 species of insects around the world shows that butterflies, bees and other flying insects in particular are prevented from migrating to higher altitudes because there is not enough oxygen to survive.
Many species lack clear climate strategies
Overall, evolutionary adaptation appears to help reduce the impacts of global warming, but the evidence so far shows that it is insufficient to overcome current rates of climate change. Acclimation and migration provide faster solutions, but research shows that these may not be enough, either.
Of course, not all evolution is driven by warming temperatures. Plant and animal species appear to be gradually adapting to other types of environment, including human-made environments such as cities. But the rapid pace of global warming makes it one of the major threats to which species must respond immediately.
The evidence shows that humanity cannot accept that plants and animals will be able to save themselves from climate change. To protect these species, people will have to stop the activities that encourage climate change.
This article is republished from The Conversation, a non-profit, independent news organization that brings you facts and analysis to help you make sense of our complex world.
It was written by: Michael P. Moore, University of Colorado Denver and James Stroud, Georgia Institute of Technology.
The authors do not work for, consult with, or own shares in, or receive funding from, any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.