John Muir said that, “when we try to pick out anything by itself, we find it hitched to everything else in the Universe”.

“sky island” in Arizona of cooler pine forest surrounded by desert

That is exactly what ecologists from the University of Montana found during a 6 year study in high elevation areas of Arizona. In the picture on the right you can see a “sky island” comprised of high elevation snow-dusted pine forest surrounded by lowland desert. These areas are hotspots of biodiversity and endemism (areas with species that are found nowhere else).

It was in high elevation Arizona that researcher’s Thomas E. Martin and John L. Maron discovered an intricate connection between climate change, the behavior of elk (Cervus canadensis), local plant life, and the fate of songbirds. They documented how climate change is effecting all of these players in the food web.

Less snow pack at high elevation means that elk hang around and eat the songbird habitat

Martin and Maron discovered that declining winter snow pack at high elevations means that elk do not feel as much pressure to migrate to lower elevations during winter. Moreover, the lack of snow leaves deciduous tree species, such as aspen, vulnerable to being eaten.  This results in a much more open landscape, and is detrimental to the habitat of migratory songbirds. The presence of thick deciduous vegetation at high elevation is essential for many songbirds to breed and raising offspring successfully.

Essentially, winter snow pack in this system acts as a habitat preservation mechanism for songbirds.

The Red-faced Warbler is one species affected by the climate driven changes in elk behavior

When the snow does  not arrive, it has a cascade of non-intuitive effects via altering the behavior of elk that can be detrimental for avian biodiversity. This is a good example of the indirect and hard-to-predict effects of climate change on ecosystem functioning.

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Full citation of the original scientific article:

Martin, T. E., & Maron, J. L. (2012). Climate impacts on bird and plant communities from altered animal-plant interactions. Nature Clim. Change, 2(3), 195–200. Retrieved from http://dx.doi.org/10.1038/nclimate1348

photo credit: sky island- Brambleshire via wikipedia; featured image (redfaced warbler)- Tom Benson via flikr; elk- Michael Jefferies via flikr