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Who Might Inherit the Earth?

words by liana demasi

Evolution has seen species adapt along with their environment for millennia. But the inconsistent and rapid effects of climate change are making it difficult for some to keep up.

With eyes peeled toward the future, climate change discourse has long considered what a ravaged world might look like. The speculation wavers between a saved utopia, in which communal living is made possible by the eradication of capitalism and the reliance on fossil fuels; a semi-livable planet shrouded by destruction, mass migration, carnage, and death; or a dismal wasteland, run rampant with vultures, rats, raccoons, and cockroaches. As more and more IPCC reports are released, in combination with actions like the roll-out of 180 million reserve barrels of oil by the Biden Administration and the stagnated efforts to elevate clean energy, the prospect of a utopia—or rather, a world saved —grows smaller in the rear view mirror. What’s more likely is a mixture of a semi-livable planet and a wasteland.


But are we destined for a world where scavengers reign superior? Or might some species evolve and adapt to this changing world?


“Generalist species have an advantage in times of rapid change,” says conservation biologist and author, Thor Hanson. “When things are stable over periods of time, the advantage goes to specialization because of the steady competition.” Hanson goes on to describe a phenomena called ‘niche partitioning’ in which multiple bird species eat and nest in separate, designated parts of a tree. Every species has shelter and a food supply, making for a healthy, reliable cycle. However, if that environment rapidly changes, it’s the specialist species that would suffer. Their habitats or food supply rapidly decline, and since they have become accustomed to their specialization, their bodies are less likely to withstand the demands of their new environment or process alternative food options. By contrast generalist species are able to eat nearly anything and adapt quickly.


The Anthropocene has become synonymous with mass extinction, leaving the world’s species on a spectrum of safety. Environmental shifts have long triggered evolutionary and adaptive changes in animals, but the swiftness of this crisis has left many species teetering on the edge of extinction, with some pushed over that edge. As evolution has indicated, species can shift along with their environment, but with the inconsistent and rapid effects of climate change, the window of time is minimal, making it difficult for many species to keep up.


“The first mammal to go extinct, that we know of, because of climate change were the Bramble Cay melomys in Australia, because its habitat is now completely flooded due to sea level rise,” says Hanson. “If the melomys were able to develop gills in three or four generations, they would have been able to survive. If we could stretch out the changing climate over several million years, there would be more opportunity for major evolutionary adaptations. But those massive changes are not possible in the time frame we’re working with.” In other words: the amount of time it would take for land dwellers to evolve into sea creatures, or animals to achieve a processing power strong enough to withstand plastic, will most likely surpass the amount of time these species have to evolve under the deteriorating circumstances.

Are we destined for a world where scavengers reign superior? Or might some species evolve and adapt to this changing world?

Liana DeMasi

According to evolutionary biologist and retired Cornell professor, Nelson Hairston, “Populations that have many more individuals and short generation times are going to be the most likely to adapt. Algae have a generation time of a day, and crustaceans are a few weeks or a month, while larger fish are at a year or more with much smaller populations. The chances of a favorable mutation occurring are much lower in those species.” This is why the phrase “Mass Extinction” is used—and why it’s so potent. But, while the time required for mass changes takes many generations, there are recent studies that indicate smaller evolutionary shifts are possible.


“We saw inherited genetic change driven by climate change with the Anole lizards,” says Hanson, referring to the subject of his book, Hurricane Lizards and Plastic Squid. Hanson is speaking to a study that measured the Anole lizards before and after hurricanes Irma and Maria hit Turks and Caicos in 2017. After the storms, those that survived were found to have had 10% larger toe pads than those who perished. This discernible change was made to increase their grip on trees, which in turn increased their chances of survival. The others were whisked away by high winds. “They had measured survival of the fittest playing out in a short time frame,” Hanson adds.


By studying hurricane patterns in other regions over many generations, these scientists saw that this evolutionary change persisted. Meaning, other lizards that were exposed to more frequent hurricanes had grown larger toe pads, while others that were not exposed did not. These types of changes typically happen at a much slower pace, but the swiftness at which the environment is changing has enabled these shifts to happen much sooner. It’s for this reason Hanson believes that we can expect to see more of such changes in other species.


But, these evolutionary successes don’t overshadow the conditions of other locations that make evolution less probable.

“If species keep getting pushed to colder climates, eventually they’ll have nowhere else to go because those places will no longer exist.”

Tess Grainger
Postdoctoral Fellow at the University of British Columbia

The majority of living creatures inhabit places gravely impacted by human activity. Not only are they combatting a human-caused climate crisis, they also face a number of other adversaries that are adding to the issue at hand, including the more immediate destruction of their food supplies and shelters. From mass construction to deforestation, travel, and the overconsumption of resources, many habitats and spaces are becoming unliveable at faster rates than they would from just climate change alone.


In the case of diminishing habitats, migratory species have higher chances for survival. Take the salmon, a fish that depends on cold water for oxygen. As water temperatures rise, salmon naturally seek colder water. This ability and proactivity to move around will likely prolong their survival—at least for some time. Because as temperatures continue to rise, the cooler spots they search for dwindle. And these rising temperatures combined with the building of dams and transportation systems on freshwater rivers where salmon spawn, brings the long-term survival of this species into question. Might there be another river in which to spawn? Perhaps. But human-made blockades and a larger existential crisis doesn’t make for easy living.


“The most immediate, two degree shift in temperature has much more micro-impacts on species and adds risk of extinction,” says Tess Grainger, a postdoctoral fellow at the University of British Columbia.  “If species keep getting pushed to colder climates, eventually they’ll have nowhere else to go because those places will no longer exist.”


We find adaptation admirable, especially within our own species. But should we be forced into it? And should we force others with less agency to do the same? In a simulated study, Tess Grainger found evolutionary changes in fruit flies, discovering that they “evolved…to be larger, lay fewer eggs and develop faster” when exposed to a predatory, invasive species over the course of one summer and the subsequent fall. These types of rapid evolutionary changes are documented, as are the adaptational qualities of generalist species. However, these changes are not equal in likelihood to the survival of animals like vultures, rats, or cockroaches. Some species are predisposed for survival under extreme conditions, whereas others can migrate to more inhabitable places. It’s too soon to say which of us might still wander the planet in many decades to come if climate change continues its course.


So, the question remains. Who might inherit a desecrated Earth? According to Thor Hanson: “A species cannot adapt to a habitat that is no longer there.”

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