SAVING MOUNTAINTOP SPECIES FROM WARMING
Mountains provide some of the world’s most spectacular landscapes and host an amazing diversity of species and habitat types. Within just a couple of miles on a mountain, one can travel through the kinds of ecosystems that are otherwise separated by many degrees of latitude on the earth’s surface. These high-elevation areas provide islands of suitable habitat that many species depend on for survival. And humans depend on mountain ecosystems, too — for recreation, spiritual renewal and a wide range of resources. In fact, half the world’s human population directly depends on the freshwater resources that mountains provide.
Unfortunately, global warming is a grave threat to the health of mountain ecosystems, which in some cases are projected to experience early and magnified effects of climate change. Mountains can act as refuges from environmental change, but mountain species that have narrow habitat tolerance and limited dispersal abilities — particularly those confined to the highest elevations — are at a frightening risk of being lost because of climate change. Mountain-dwelling animals and plants are already seeing their habitats shift and shrink as a result of climate-change-induced temperature increases, which force many species to move upslope. High alpine zones are at risk of disappearing completely, leaving species that live there trapped on the summits until they’re pushed to extinction. In some regions, temperature change is magnified at mountaintops. Studies in the European Alps have shown as much as a fivefold temperature increase on peaks compared to the global average. Temperature increases on mountains are also changing the global hydrological cycle. In the western United States, for example, snowpack is declining and snowmelt-driven streamflow is shifting to earlier in the year, leading to greater water stress in summer months.
The white-tailed ptarmigan, a unique ground-nesting bird, lives entirely in alpine environments. This bird will see its alpine habitat constricted by a rising tree line, and without the ability to travel long distances to more suitable mountain ranges further north, the white-tailed ptarmigan faces a grim future in the conterminous United States. Other species, such as the Sierra Nevada bighorn sheep, depend on alpine and subalpine meadows for food during part of the year — as meadows shrink, this iconic symbol of western wilderness may go hungry. The cold-adapted American pika can die from overheating in the summer and from cold stress in the winter as diminished snowpack leaves it vulnerable to cold snaps. More than a third of documented pika populations in the Great Basin mountains of Nevada and southern Oregon have gone extinct in the past century amid rising temperatures. Species that live downslope will also be hurt by changes on mountaintops; the Sierra Nevada mountain yellow-legged frog, for example, depends on runoff from snowpack year-round to support its three-to four-year life stage as a tadpole, and earlier spring snowmelt runoff caused by global warming may leave this hardy, once-abundant creature high and dry in the summertime.
The Center has long been a leader in protecting species from global warming, and mountaintop species are no exception. We’ve been working for the Sierra Nevada mountain yellow-legged frog since 2000, for the Sierra Nevada bighorn since 2005 and for the American pika since 2007. As the stakes continued to rise exponentially for mountain species, in summer 2010 we stepped up our campaign by filing simultaneous scientific petitions to protect the white-tailed ptarmigan, Bicknell’s thrush, i’iwi and San Bernardino flying squirrel under the Endangered Species Act.
The terrible damage to mountaintop wildlife and ecosystems due to global warming should stand as a warning to humanity. Endangered Species Act protection is necessary to safeguard warming-threatened mountain species from all threats, as well as protecting their habitats — and the planet — from runaway global warming by helping spur strong measures to reduce greenhouse gas emissions on the local, national and international scale. And because humans depend on mountaintop ecosystems for elements essential to our survival, swift, decisive action on global warming is for our own sake as well as for the sake of other species that share our earth.