Annals of Global Warming: Dramatic Links Found Between Climate Change, Elk, Plants, and Birds

Understanding the physics of the Earth’s atmosphere poses great problems — it is an astonishingly dynamic, fluid environment.  Understanding the relationships between species in ecosystems is no less complex, and no less vexing.

Wise followers of science recognize that when findings in biology, chemistry and physics, point the same direction, something powerful creates the convergence, and is not to be ignored.

So it is with these findings from the University of Montana and the U.S. Geological Survey, demonstrating clear links between climate change and the changing life patterns of large animals like elk, small animals like birds, and the plants the animals live in and consume.  This study is so complex that climate denialists haven’t figured out which part to deny, yet.  (This press release came out in January.)

From the USGS, with no adornment from the Bathtub, a press release on a letter in Nature Climate Change:

Dramatic Links Found Between Climate Change, Elk, Plants, and Birds

Released: 1/9/2012 11:30:00 AM

U.S. Department of the Interior, U.S. Geological Survey
Office of Communications and Publishing

In partnership with the University of Montana

Missoula, MT – Climate change in the form of reduced snowfall in mountains is causing powerful and cascading shifts in mountainous plant and bird communities through the increased ability of elk to stay at high elevations over winter and consume plants, according to a groundbreaking study in Nature Climate Change.

Red-faced warblers are one of the species affected by climate change in the form of reduced snowpack in the Arizona Mountains, according to a USGS Montana Cooperative Wildlife Research Unit study. Photo by Tom Martin, USGS, May 1998, in the Coconino National Forest

The U.S. Geological Survey and University of Montana study not only showed that the abundance of deciduous trees and their associated songbirds in mountainous Arizona have declined over the last 22 years as snowpack has declined, but it also experimentally demonstrated that declining snowfall indirectly affects plants and birds by enabling more winter browsing by elk. Increased winter browsing by elk results in trickle-down ecological effects such as lowering the quality of habitat for songbirds.

The authors, USGS Montana Cooperative Wildlife Research Unit scientist Thomas Martin and University of Montana scientist John Maron, mimicked the effects of more snow on limiting the ability of elk to browse on plants by excluding the animals from large, fenced areas. They compared bird and plant communities in these exclusion areas with nearby similar areas where elk had access, and found that, over the six years of the study, multi-decadal declines in plant and songbird populations were reversed in the areas where elk were prohibited from browsing.

Hermit thrushes are a songbird species that was strongly affected by plant community changes in mountains because of reduced snowpack and cascading ecological effects, according to a USGS Montana Cooperative Wildlife Research Unit study. 2005 photo by Tom Martin, USGS, in the Coconino National Forest

“This study illustrates that profound impacts of climate change on ecosystems arise over a time span of but two decades through unexplored feedbacks,” explained USGS director Marcia McNutt. “The significance lies in the fact that humans and our economy are at the end of the same chain of cascading consequences.”

The study demonstrates  a classic ecological cascade, added Martin. For example, he said, from an elk’s perspective, less snow means an increased ability to freely browse on woody plants in winter in areas where they would not be inclined to forage in previous times due to high snowpack. Increased overwinter browsing led to a decline in deciduous trees, which reduced the number of birds that chose the habitat and increased predation on nests of those birds that did choose the habitat.

When elk are excluded, aspen growth dramatically increases - Climate change in the form of reduced snowfall in mountains is causing powerful and cascading shifts in montane plant and bird communities through the increased ability of elk to stay at high elevations over winter and consume plants. Here, you can see an example of the difference in aspen growth inside versus outside a fence that excludes elk. Photo by Tom Martin, USGS, in Coconino National Forest

“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,” Martin said.

The study, Climate impacts on bird and plant communities from altered animal-plant interactions, was published online on Jan. 8 in the journal Nature Climate Change.

Elk in winter at Camp Creek Feed Ground, Northwestern Wyoming - USGS photo

More:

• Abstract of the letter at the Nature Climate Change site:  Nature Climate Change 2, 195–200 (2012)  doi:10.1038/nclimate 1348; Published online 10 January 2012
• Interview with Maron and Martin about the study from MTPR (Montana Public Radio) (tip of the old scrub brush to the Clark Fork Coalition)
• Billings Gazette story on the study, “UM study links climate change, decline in songbird populations”