Warming: A bad climate for endangered species?

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Warming: A bad climate for endangered species?

On Feb. 1, 2013, the U.S. Fish and Wildlife Service proposed adding the wolverine — a tough, reclusive carnivore that lives in the snow in the Rocky Mountains — to the endangered species list. About 300 of these weasel relatives survive amid the heavy snows and severe climate of the high mountains, but global warming is melting their habitat.


Stance and face give a wolverine the appearance of a small bear as it pads across snow.

Wolverine at an outdoor museum in Skansen, Sweden. Wolverines in the western United States are growing scarce, likely due to a warming climate that is decimating the snowy habitat they require.

The International Union for Conservation of Nature (IUCN) lists 10,820 animal species worldwide. The group’s “Red List” does not distinguish endangered from threatened species.

And now comes the accelerating threat of global warming, a planet-size problem that is sure to make matters worse for rare species in many places and cases. Polar bears and corals have already entered the list of species in danger due to the global changes wrought by greenhouse gases, and more species are doubtless coming, due to changes in precipitation, temperature, disease, ocean acidity, and the timing of flowering, fruiting, migration and the very seasons on our planet.

The Wolverine — no relative of the wolf — is perfectly adapted to the snow, with paws serving as natural snowshoes and dens deep below the snow that are warmed by the lack of wind and insulation from the snowpack. The animals “use snow as a natural refrigerator, caching their food in natural ice boxes,” to sustain them as they bear and nurse their young, says Jonathan Pauli, an assistant professor of wildlife ecology at the University of Wisconsin-Madison. “They are losing this natural refrigerator, which is really problematic because it affects this nutritional pinch point in early spring.”

The wolverine and other snow-dependent mammals are on a collision course with a warming climate, says Pauli. “The winter climate in particular in the Northern hemisphere is changing dramatically. In the last 100 years, we’ve seen an increase of three-quarters of a degree Celsius, and what’s especially relevant is the shortening of the duration and depth of the snow cover. The snow season is being compressed,” he says.


Furry brown animal, resembling a mix of small raccoon and large ferret, with long tail climbing tree trunk.

Courtesy Jim Woodford
The American marten is a carnivore that spends a lot of time under the snow. Efforts to reintroduce the marten in Wisconsin have faltered, possibly due to a changing climate.

The American Marten is another winter specialist that hunts mice under the snow, but some populations are in trouble. “They are a winter-adapted carnivore,” says Pauli. “They are light and their feet, like the wolverine, are a natural snowshoe” that saves energy. Sinking into deep snow is tiresome and “can put you on the nutritional redline. It’s not just exhausting, it can be deadly.”

Graph showing average global temperature rising since ~1910; rising above 1901-2000 average in 1970.

The signature of global warming can be traced to about 1980. All of the top 10 warmest years, including 2012, occurred after 1997.

The American marten was extirpated from Wisconsin in the 1920s, and reintroduced in the 1950s and again in the 1970s, but they are not prospering, and one possible explanation is the truncated snow season, Pauli says.

Turning turtles

It’s tough to pinpoint the role of a changing climate on endangered species. After all, as pioneering ecologist Barry Commoner said, the first law of ecology is that everything is connected to everything else; nothing exists in isolation. “I don’t know how much hard data there is on a lot of species relative to climate change,” says Scott McRobert, professor of biology at Saint Joseph’s University in Philadelphia. “Although it is probably causing dramatic effects to a large number, it’s hard to isolate climate change from other factors.”

That calculus is evident in the leatherback marine turtles which “have declined exponentially since we started studying them in 1989,” due to hunting of turtles, gathering of eggs, and fishing gear that snared turtles as “by-catch,” says James Spotila, professor of environmental science at Drexel University.

Changing climate is fueling more of the periodic warmings in the central Pacific called el Niño, Spotila says. “When the Pacific warms, there is less [nutrient-rich] upwelling, so the turtles have a harder time getting food,” which impairs growth and reproduction, he says. “Our studies and mathematical model show they will be gravely affected by a changing climate, and it’s starting now.”

Leatherback sea turtles: from eggs to hatchlings

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Leatherbacks and other marine turtles face a second difficulty related to warming: The sex of hatchlings is determined by temperature while the egg develops; when it’s hotter, more females develop. The result is that most turtles developed from eggs laid in January and February are female, says Spotila.


Hand drawing of finch-sized lemon-lime birds with long, narrow, curved beaks.

Hemignathus procerus, or Kauai akialoa, is endemic to the island of Kaua’i, Hawai’i. The endangered honeycreeper eats insects and sucks honey from tube-shaped flowers. Over two centuries, Hawaiian honeycreepers have suffered many assaults and extinctions. According to a 2011 study, avian malaria is spreading as global warming expands the habitat of its mosquito vector.1 Looking at data on more than 3,000 bird species from seven decades, the authors linked a two- to three-fold increase in bird malaria to about 1°C temperature rise.

On Colombia’s Caribbean coast, 92 percent of leatherbacks are born female in some years, and the temperature anticipated for 2050 will make virtually all of them female. Indeed, a 2012 study.2 warns that “complete feminization could occur, as soon as the next decade.”

Without males, a population crash is inevitable.

Heat by itself is also a problem, says Spotila: “As the season progresses, the hatchlings become weaker and more heat stressed. In April [on Costa Rica’s Pacific Coast], there is very low hatchling success due to heat stress.”

Climate change is “a giant bummer,” Spotila says. “We spent 23 years setting up Las Baulas National Marine Park, protecting the beach, and getting a handle on fishing. … The overwhelming effect of global warming is going to make life even more difficult. We are going to see species after species getting these problems.”

Walking that long Amazonian road

In the vast tropical forests that survive in Amazonia, climate change will scourge many habitats, according to a new study.3 Kenneth Feeley, assistant professor of biology at Florida International University, asked how far residents of large ecological situations — biomes — would have to move to find suitable habitat by 2050. “The classic way has been to look at the effect of deforestation or fragmentation as almost one field of conservation biology, and a separate field of climate change ecology,” Feeley told us. “There hasn’t been that much study of both simultaneously.”

Feeley combined these threats. “We looked at the conditions you find in a spot in the Amazon, and asked where would you have go to find the same temperature and precipitation” in 2050, he explains.

And he then blocked off areas that would require traversing large, deforested areas. Already, he notes, many Amazonian animals “are really hesitant to cross a break, a trail, a road or a river,” so requiring animals to avoid deforested areas “shows the true distance that a species has to move.” Large-scale deforestation “creates environmental traps for species, because there is no way to reach the future climate area without crossing a deforested area,” Feeley says.

In many cases, he says, animals would have to travel “off the map.”

Minimum distance to suitable habitat in Amazonia, 2050

Left: Map of Amazon for 2050. most organisms will have to migrate at least 200 kilometers to find suitable habitat.
Right: Map of Amazon for 2050. Most organisms will have to migrate up to 1,000 kilometers to find usable habitat, some find no habitat.
Map at left shows how far species would have to move to find today’s climate after expected changes in temperature and precipitation. Map at right adds in effects of deforestation. Because most organisms cannot cross farm fields, they will have to travel much further to find livable habitat. Organisms now living in the black zones will be homeless.
Both maps used with permission; Feeley and Rehm. Amazon’s vulnerability to climate change heightened by deforestation and man-made dispersal barriers. Global Change Biology. Blackwell Publishing Ltd.

We commented that his maps were profoundly depressing, and Feeley cheerlessly reframed them as best-case scenarios. Organisms, he noted, are inter-dependent: If bird A is needed to pollenate flower B, “that just compounds the difficulties, because both have to arrive simultaneously. And they might depend on a third species. If they do not all arrive simultaneously, it might be impossible for each species to be there.

“The forecast for Amazon biodiversity is really grim,” says Feeley. “Our only hope is that we are wrong.”

What to do?

Scientists are starting to test some tentative fixes for the biodiversity ravages blamed on a changing climate. Many proposals favor preserving more habitat, while choosing more selectively. “We can envisage ways to manage land cover that would mitigate or reinforce the changes we expect,” says Pauli. For example, “Different land-cover types can have a strong effect on ambient conditions in winter; areas with forest cover can have much more moderate temperature than open areas.”

Here are some other ideas we culled from a survey of the changing landscape of hot-world biodiversity preservation:

✻ Mapping migration

The new maps of Amazonia could help in designing migration corridors so species can move as climate changes, says Feeley. “If we know this area will be lost to agriculture, can we plan to place corridors in the most effective places? A lot of the focus in conservation has been on preserving parks, assuming static conditions. Now we are talking more about the need to protect areas to allow species to respond to climate change,” he says.

✻ Change the habitat

Since temperature controls the sex ratio in leatherbacks, Spotila and others are testing whether fresh-water sprinklers and sunshades can cool the beach in Costa Rica to stabilize the male-female ratio and improve hatching success. “We are doing the experiment now, trying to determine which of those options will work,” he says.

Aided by the Climate Adaptation Fund, the Grand Canyon Trust is reintroducing beavers into 87 stream segments in Southern Utah. Rollover to see the change one year later: the new beaver pond has already drowned invasive plants while creating habitat for native plants and animals. Check the video.
First: July 2011, photo by Natalie Jamerson, Whitman College; second: September 2012, photo by Allison Bolgiano, Whitman College

✻ Put wildlife to work!

Beaver dams naturally store water, replenishing aquifers and restoring wetlands for wildlife, while reducing floods and the effects of drought. Now, after centuries of trapping, beavers are returning (via foot or truck) to various landscapes, including the arid Southwest, faced with drought and highly erosive floods in the changing climate.


With brown-scaled body stretching behind, lizard turns face to the camera with open mouth and outstretched dark blue tongue.

Photo by Peter Shanks
The beautiful blue-tongued lizard, under threat from habitat disturbance and a changing climate, could be moved to better habitat around its native range in southern Australia.

✻ Trucking to a better home?

Moving animals to habitat that remains hospitable in the new climate may be a last resort for animals like the endangered blue-tongued lizard, whose native grasslands in South Australia have been transformed by farmers and now climate change. Some scientists have proposed building artificial burrows for the lizards, and even moving them to new locations where the future’s climate should be more benign. “Although we recognize the importance of conservation efforts to improve the quality, connectivity and permeability of the species’ current habitats, the rapidity of climate change will continue to exceed the ability of some species to adapt or disperse to more climatically favorable regions,” wrote the authors of a 2012 relocation study.4

✻ More shelter from the storm

Captive breeding has been used to sustain whooping cranes and other animals threatened with extermination in the wild, and McRoberts keeps several endangered turtles from Asia or South America in “assurance colonies” in his lab. “At least we can keep some of them alive in the hope that there might be places where they could live in the wild,” he says. As McRoberts recognizes, captive breeding could deflect time and energy from habitat conservation. “Even as someone who does it, I am not saying it’s an optimal way of saving species, but I don’t see it detracting from survival in the wild,” he says. “It’s best to approach any conservation issue from as many different points of view as you can.”


Two tiny turtles side by side, legs retracted into shells and spotted faces peering out.

Geoclemys hamiltonii, AKA black pond turtle or black spotted turtle, in the McRoberts lab. These threatened turtles eat snails and fish in rivers and ponds with abundant aquatic vegetation in India, Pakistan and Bangladesh.
Courtesy Scott McRoberts, Saint Joseph’s University

Endangered Species Act to the rescue?

Our story started with the potential listing of the wolverine under the Endangered Species Act, a pioneering law premised on the avoidance of extinction. But a 2012 study5 of ESA plans for endangered species in the American West found that “few [climate] adaptation projects have made it to the implementation phase,” due to budget constraints and lack of specific direction from the government agencies involved.

Newer habitat conservation plans should pay more attention to climate, says study author Paola Bernazzani, of the Ohio consulting group ICF International. “There are some good plans coming out in the future, but since we looked retrospectively, there was not anything that did a good job,” she says.

The inability to pinpoint the details of future climate and habitat should not excuse the failure to plan for changes, Bernazzani says. “We admittedly don’t know everything we would like to know to plan for 30 or 50 years, but … the Endangered Species Act was written to anticipate flexibility by calling for adaptive management.”

In a forthcoming plan, Bernazzani says, her company is using computer modeling to explore how fish will move through hydroelectric dams: “We are able to alter the scenarios to fit different climate-change assumptions, and we’ll test them. It’s like a fire drill — you know before implementation what are some potential outcomes.”

Habitat plans may also require establishing preserves to buffer against climate change, Bernazzani says, but the reality is that “we are talking about species that are already rare, and adding one other pressure on top, and I am not sure all the conservation planning in the world is going to solve that.”


Columns of usually rusty orange coral faded to bright white.

Coral “bleaching” was one of the first recognized biological damages of global warming: When water warms, the coral animals expel the symbiotic partners that feed them, and the coral turns white. Unable to eat, the coral can die if temperatures stay too warm. Bleaching has started in the center of this coral in Indonesia, but coral remains alive around the edges.

The bottom line

Back in the 1980s, climate change was tomorrow’s trouble. Not any more. “There is no question that climate change poses an unprecedented challenge to biodiversity,” says Pauli, the mammologist at the University of Wisconsin-Madison. “It’s one of the biggest conservation crises we are facing.”

To a specialist in winter ecology such as Pauli, the truncation of the snow season “is challenging and frustrating, but it does provide an opportunity to understand the winter system; it’s an experiment that unfolds in real time.”

The reality is that the disruptions due to climate change are seamlessly connected to everything else, says McRoberts. “It’s always very difficult to say a species is encountering difficulty from one direction, and every endangered species is also encountering other problems, habitat destruction being the primary one,” he says.

McRobert agrees that it can be daunting for people who have worked for decades to preserve biodiversity to gird themselves to combat a threat with a global reach. “There are so many issues that you can be overwhelmed easily,” he says. “If you are worried about habitat for endangered species, you should keep working on that” instead of worrying specifically about climate change. “It’s hard to address everything at once.”

David J. Tenenbaum


Terry Devitt, editor; Emily Eggleston, project assistant; S.V. Medaris, designer/illustrator; David J. Tenenbaum, feature writer; Amy Toburen, content development executive


  1. Climate change increases the risk of malaria in birds, Laszlo Garamszegi, Global Change Biology (2011) 17, 1751–1759, doi: 10.1111/j.1365-2486.2010.02346.x
  2. A potential tool to mitigate the impacts of climate change to the Caribbean leatherback sea turtle, Juan Panito-Martinez et al, Global Change Biology (2012) 18, 401–411, doi: 10.1111/j.1365-2486.2011.02532.x
  3. Amazon’s vulnerability to climate change heightened by deforestation and man-made dispersal barriers, Kenneth J. Feeley et al, Global Change Biology (2012) 18, 3606–3614, doi: 10.1111/gcb.12012
  4. Managed relocation as an adaptation strategy for mitigating climate change threats to the persistence of an endangered lizard, Damien Fordham et al, Global Change Biology (2012) 18, 2743–2755, doi: 10.1111/j.1365-2486.2012.02742.x
  5. Climate change and western public lands … K.M. Archie et al, Ecology and Society, 17:(4) 20, 2012
  6. Slideshow:Great extinctions and great species recoveries featured at the Natural History Museum in London
  7. USGS Scientists answer questions about climate change in the mountains
  8. Who fades first? Pikas: the climate change sentinel species
  9. Worried about trout? See how they fare under climate change preditictions
  10. Hungry for more leatherback facts?