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Seals, birds, and alpine plants suffer under climate change

The number of species identified by scientists as vulnerable to climate change continues to rise along with the Earth’s temperature. Recent studies have found that a warmer world is leading to premature deaths of harp seal pups (Pagophilus groenlandicus) in the Arctic, a decline of some duck species in Canada, shrinking alpine meadows in Europe, and indirect pressure on mountain songbirds and plants in the U.S. Scientists have long known that climate change will upend ecosystems worldwide, creating climate winners and losers, and likely leading to waves of extinction. While the impacts of climate change on polar bears and coral reefs have been well-documented, every year scientists add new species to the list of those already threatened by anthropogenic climate change.



Ice Troubles



A new study in PLoS ONE has found that harp seal pups are dying en masse due to a decline in winter sea ice.



“The kind of mortality we’re seeing in eastern Canada is dramatic. Entire year-classes may be disappearing from the population in low ice years—essentially all of the pups die,” explains David W. Johnston with the Duke University Marine Lab in a press release. “It calls into question the resilience of the population.”


Harp seal. Photo by: Matthieu Godbout.
Harp seal. Photo by: Matthieu Godbout.

Harp seals require old stable sea ice for birthing and nursing their pups. Mother harp seal can nurse a pup in an incredibly brief period: 12 days. However given rapid melting and low ice cover, even 12 days may be asking too much.



“As a species, they’re well suited to deal with natural short-term shifts in climate, but our research suggests they may not be well adapted to absorb the effects of short-term variability combined with longer-term climate change and other human influences such as hunting and by-catch,” Johnston said.



The study found that harp seal populations in eastern Canada fluctuated with sea ice cover in the region. Little ice cover and a weak North Atlantic Oscillation (NAO), which also impacts seasonal ice, were found to correspond to a high level of dead pups.



“Regardless of NAO conditions, our models show that sea ice cover in all harp seal breeding regions in the North Atlantic have been declining by as much as 6 percent a decade over the study period,” Johnston said, adding that “the losses in bad years outweigh the gains in good years.” The study’s findings correspond to observations: seal hunters and conservationists have reported seeing seal pups drown during low ice years.



Despite the perils of climate change to their ecosystem, harp seals are currently listed as Least Concern by the IUCN Red List due to a large population of around 8 million animals. They are the most heavily hunted of the world’s seal species.


Earlier Springs



While some people may be happy to see Spring arrive a little earlier, it can wreak havoc on migrating species that depend on nature’s seasonal rhythms. A recent study in Global Change Biology links climate change to the mystery of missing migrating ducks in Canada. Two types of migrating ducks, scaups and scoters, incorporating a number of species, have seen populations drop to around half in Canada since the 1970s, but researchers have had little luck explaining why. Now, however, they believe they know the cause: earlier Springs mean the ducks are missing out on prime feeding time.



“Because of climate change, the ducks don’t have the food that they need when they need it,” Stuart Slattery, a research scientist with Ducks Unlimited Canada, told CBC News.


Greater scaup (Aythya marila). Photo by: Calibas.
Greater scaup (Aythya marila). Photo by: Calibas.

According to the study, Spring is arriving around 11 days earlier than it did 35 years ago in the ducks’ breeding grounds. But scaups and scoters have not adjusted to this; by the time they arrive they miss out on some of the best feeding days, ruining the chance to nest twice.



“As this mismatch gets worse, the ducklings are impacted the most,” says Slattery. “The food just simply isn’t there in the amounts that it was historically.”



Slattery adds that not all ducks are arriving late: mallards appear to have adjusted to the changing rhythms, but there is no certainty that the scaups and scoters will eventually learn. It may be that the change is simply happening too quickly for them.



“We are experiencing climate change in a very real way,” he concluded.


Alpine Meadows



Some plant species are also finding it difficult to adapt. A recent study in Nature Climate Change, found that mountain vegetation across Europe, covering 867 sites over 60 different summits, has suffered from drastic climatic changes in just seven years: between 2001 and 2008.



“We expected to find a greater number of warm-loving plants at higher altitudes, but we did not expect to find such a significant change in such a short space of time,” lead author Michael Gottfried from the Global Observation Research Initiative in Alpine Environments (GLORIA) program said in a press release.


This alpine species (Nevadensia purpurea) could disappear from some European mountains in the next few decades. Photo by: Harald Pauli.
This alpine species (Nevadensia purpurea) could disappear from some European mountains in the next few decades. Photo by: Harald Pauli.

The study, the largest of its kind yet conducted worldwide, found that some alpine meadows could vanish entirely within just a few decades. Higher summer temperatures in the mountains are pushing alpine species upward and allowing lower altitude species to colonize new areas. Researchers have dubbed this process “thermophilization.”



“Many cold-loving species are literally running out of mountain. In some of the lower mountains in Europe, we could see alpine meadows disappearing and dwarf shrubs taking over within the next few decades,” Gottfried warned.



What’s the solution? Given that cold-loving plants will not adapt to a warmer climate, there’s only one answer according to Gottfried: “we must concentrate on mitigating climate change in order to preserve our biogenetic treasure.”


Indirect Impacts



Climate change is also having an indirect impact on species. Ecosystems are by their nature complex, and one change, such as warmer temperatures, is likely to drive unexpected shifts. Scientists in the U.S. were particularly surprised to see mountain plants and birds in the U.S. hurt not only by higher temperatures directly, but by the elk that took advantage of them.



Elk are considered “apex consumers,” in other words they have an inordinately large impact on their ecosystems. The presence of elk can change plant communities, which in turn impact species all down the line.



In the case of climate change, researchers writing in Nature Climate Change found that higher temperatures and precipitation changes have resulted in reduced snowfall in some U.S. mountain ranges. This decline in snow cover has meant that elk herds have stayed longer in mountain ecosystems browsing to their heart’s content. But this overbrowsing by elk decreased deciduous tree survival and degraded prime habitat for songbirds. Researchers mimicked the impact of longer elk-browsing versus elk-absence in controlled fenced areas to measure how songbirds and trees fared.



“This study demonstrates that the indirect effects of climate on plant communities may be just as important as the effects of climate-change-induced mismatches between migrating birds and food abundance because plants, including trees, provide the habitat birds need to survive,” explained U.S. Geological Survey (USGS) director Marcia McNutt in a press release.


Climate change and extinction



Climate change is caused by burning fossil fuels, such as oil, gas, and coal, and other activities that emit carbon like deforestation. Global temperatures are currently 0.8 degrees Celsius (1.44 degrees Fahrenheit) higher since the Industrial Revolution. The 13 warmest years on record have all occurred in the last 15 years with the 2000s being the warmest decade to date. Scientists have argued for decades that the only way to mitigate climate change is to cut greenhouse gas emissions.



Past studies have projected that a warmer planet will likely hurt everything from lizards to African apes, and clown fish to koalas. While it is not surprising that a warmer world will cause drastic changes to the Earth’s ecosystems, scientists have been continually alarmed at how quickly these changes are occurring. In an age when many species already struggle against the onslaught of human societies on nature—including habitat loss, deforestation, pollution, overexploitation for food or medicine, and invasive species—many biologist fear climate change could be the last straw, leading to a mass extinction.



“Ordinary people are not powerless to stop these tragic losses,” Simon Stuart, Chair of IUCN’s Species Survival Commission, said in 2009 related to the threat of climate change to the world’s biodiversity. “They can cut down on their own CO2 emissions and voice their support for strong action by their governments to change the dire climate prognosis we are currently facing.”








Four different global temperature records show the Earth is warming. Graph courtesy of the IPCC. Click to enlarge.






CITATIONS:



Drever, M.C., R.G. Clark, C. Derksen, S.M. Slattery, P. Toose, and T.D. Nudds. 2011. Population vulnerability to climate change linked to timing of breeding in boreal ducks. Global Change Biology AIP.



Michael Gottfried, Harald Pauli, Andreas Futschik, Maia Akhalkatsi, Peter Barancok, José Luis Benito Alonso, Gheorghe Coldea, Jan Dick, Brigitta Erschbamer, María Rosa Fernández Calzado, George Kazakis, Ján Krajci, Per Larsson, Martin Mallaun, Ottar Michelsen, Dmitry Moiseev, Pavel Moiseev, Ulf Molau, Abderrahmane Merzouki, Laszlo Nagy, George Nakhutsrishvili, Bård Pedersen, Giovanni Pelino, Mihai Puscas, Graziano Rossi, Angela Stanisci, Jean-Paul Theurillat, Marcello Tomaselli, Luis Villar, Pascal Vittoz, Ioannis Vogiatzakis & Georg Grabherr (2012). Continent-wide response of mountain vegetation to climate change.
Nature Climate Change. DOI:10.1038/nclimate1329.



Johnston DW, Bowers MT, Friedlaender AS, Lavigne DM (2012) The Effects of Climate Change on Harp Seals (Pagophilus groenlandicus). PLoS ONE 7(1): e29158. doi:10.1371/journal.pone.0029158



Thomas E. Martin, John L. Maron. Climate impacts on bird and plant communities from altered animal–plant interactions. Nature Climate Change, 2012; DOI: 10.1038/nclimate1348.








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