Climate Change Causes Dramatic Ecological Changes

A new multi-year study has determined that reduced winter snowfall in mountainous regions as a result of climate change is causing cascading shifts in plant life and animal communities by allowing elk to stay through winter and consume the plants that would normally be home to a variety of bird life.

When Elk are Excluded, Aspen Growth Dramatically Increases

The study was published online on January 8 in the journal Nature Climate Change and was conducted by researchers from the U.S. Geological Survey and the University of Montana.

They showed that over the last 22 years in the mountains of Arizona the abundance of delicious deciduous trees and their associated songbirds have declined as the winter snowpack has declined. However, they also experimentally showed that declining snowfall indirectly affects plants and birds by allowing more winter browsing by the elk.

The authors of the study mimicked the effects of a more average snowfall by fencing off areas of forest so that the elk could no longer reach their favoured winter foods. This allowed birds and trees to grow and thrive as if the snowfall had driven the elk away. They compared bird and plant communities in the exclusion areas with areas outside the fences and found that over the six years of their study multi-decadal declines in plant and songbird populations were reversed in the exclusion zones.

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.

“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.

Source: U.S. Geological Survey

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