To understand biodiversity loss, look at the whole globe

On June 16, the US Fish and Wildlife Service proposed that the eastern cougar be removed from the federal endangered species list. The reason: It’s extinct.

Different from western cougars and Florida panthers, the eastern cougar was federally listed in 1973, when Service biologists believed it was possible that a few of these animals still survived. They have since concluded that the last known eastern cougar died in Maine in 1938. It was trapped and stuffed, and is now on display at a museum in Saint John, New Brunswick—a testament to human short-sightedness.

“Once the most widely distributed land mammal in the Western Hemisphere, cougars have been eliminated from about two-thirds of their original range,” according to the service. But you wouldn’t know that from most news stories about cougars, which frequently leave their audiences with the impression that the animals are more numerous and dangerous than they really are. (You’re far more likely to be killed by a pet dog or a honeybee.)

A biologist studying one patch of Maine forest in the early 1930s might not have noticed that the eastern cougar was on the brink of extinction. But looking at the big picture—say, all the forests in the world—would have told a very different story. It is human nature to pay more attention to immediate threats and surroundings than to the world at large and its long-term prospects. But this narrow-minded view of the world makes it difficult to recognize global problems such as biodiversity loss and climate change, or to embrace global solutions that are the best hope for our own species as well as others.

The sixth extinction. More than 1,500 animals and plant species are federally listed as endangered or threatened. The protections afforded by listing have saved species such as the bald eagle and California condor from extinction, but only 30 species have been delisted during the past four decades because of recovery. Focusing on success stories, which represent less than 2 percent of the total species listed, gives a misleading picture of American biodiversity. Ten species on the US federal list (not yet counting the eastern cougar) have gone extinct in the meantime, and many more are candidates for listing.

The situation is much worse in many other parts of the world. A paper just published in the journal Science Advances reported that, even by a conservative estimate, the average rate of vertebrate species loss since 1900 is as much as 100 times higher than the natural rate. The authors wrote: “Although biologists cannot say precisely how many species there are, or exactly how many have gone extinct in any time interval, we can confidently conclude that modern extinction rates are exceptionally high, that they are increasing, and that they suggest a mass extinction under way—the sixth of its kind in Earth’s 4.5 billion years of history.”

Counting species is, to be sure, a tricky business. Clear-cutting a virgin forest, for example, can sometimes increase biodiversity at a specific site by creating a different kind of habitat that is hospitable to a greater number of species. But “alpha biodiversity”—the number of species within a local area or habitat—is only one measure of biodiversity.

“Gamma biodiversity”—the total species diversity across many local habitats, within an ecosystem, region, or the entire globe—can give a different picture. The world’s overall forest cover is declining markedly, for example, and while that may be a boon to species that can colonize a clear-cut, it leaves many other plants and animals homeless. The end result could be an oversupply of stump-loving species and the extinction of forest-dependent species.

Can nuclear energy save biodiversity? Deforestation and hunting are just two of the many factors contributing to the extinction of species. Experts agree that climate change is also exacerbating biodiversity loss (and will increasingly do so), and some are making a case that biodiversity should be considered along with factors such as greenhouse gas emissions and cost when choosing among future energy sources. (In fact, biodiversity is not the only consideration that should be included in such decisions. “Gamma thinking” that is global in scope would also include factors such as human health and social justice.)

A December 2014 open letter signed by 75 conservation scientists supported the conclusions of a paper published in the journal Conservation Biology, which argued that nuclear energy can play a key role in conserving biodiversity. Nuclear and wind energy, the authors argued, have the highest benefit-to-cost ratio as replacements for fossil fuels when land use is considered along with emissions and economics. This wasn’t the first letter from scientists supporting nuclear power as a low-carbon energy source, but the focus on biodiversity was unusual.

Insisting on an all-renewables approach because of “preconceived notions and ideals,” the authors wrote, could be bad for biodiversity. Hydroelectric dams, for example, “can wreak havoc on local biodiversity through flooding and by obstructing migration,” and the quest for biofuels can level fields and forests. “We have come to the evidence-based conclusion,” the authors of the journal paper wrote, “that nuclear energy is a good option for biodiversity conservation (and society in general).”

The paper is not without problems. It touts advanced nuclear reactor designs that are not yet in commercial operation and won’t be for at least another five years. Also, although the authors note that fresh water usage should be a factor in choosing the energy options least harmful to biodiversity, they fail to mention that existing nuclear power plants typically consume more water than comparable natural gas or coal plants. Because they require so much cooling water, nuclear power plants are adversely affected by both drought and sea level rise, which are expected to worsen as the planet warms.

A “gamma” climate approach. Focusing too narrowly on individual aspects of a problem—water consumption or land use, for example—is not likely to produce the best solutions to climate change. Although these factors definitely need exploration and evaluation, it’s crucial to look at the big picture, however complex it might be.

Like biodiversity, climate solutions must be studied and tackled at all levels. At the household level, for example, actions such as recycling and bicycling make sense. But focusing only on households or even individual nations isn’t enough. There may be a “war on coal” in the United States, but coal use worldwide is still growing faster than any other energy source. And Europe’s “green” climate policies are felling forests in the southern United States to make wood pellets for European power plants. Sometimes we can’t see the deforestation for the trees.

We need gamma thinking about global warming to understand what is happening in the atmosphere, oceans, and on land—and what to do about it. The danger of alpha thinking is that focusing on a particular place or time can obscure a larger truth. Temperature data for only a few years, for example, may not reveal a long-term warming trend. “Think globally, act locally” makes a nice slogan, but global action and local thinking are essential, too.

Gamma thinking about eastern cougars reveals multiple reasons for their decline. Extensive deforestation in the East played a key role by reducing habitat for deer—the cougars’ main food source. Simultaneously, overhunting of deer pressured cougars to prey more heavily on domestic livestock. This, in turn, put cougars in the crosshairs of farmers and bounty hunters.

Trees have grown back in the East, and deer have returned in numbers so large that vehicle collisions with deer kill more humans than cougars ever did. It would be useful to have a predator that could help control the population of white-tailed deer now running amok in the gardens and forests of the eastern United States. But the eastern cougar, alas, is gone forever.