Study Links Shorter Spring "Greenup" Periods, Hotter Summers To Fall In Y-Stone Elk Populations

A study commissioned to find out why there are fewer elk in Yellowstone National Park ended up shedding light on the longterm effect climate change is having on the park’s famed wildlife.

Researchers have found that the green-up period – the time from mid-April through late July when snow finally melts and meadows start to fill with wildflowers – is gradually becoming shorter, leading into the brown doldrums of summer earlier. (Updated: A link to a website about the study is here.)

The study, conducted by Wyoming Game and Fish and the Cooperative Fish and Wildlife Research Unit at the University of Wyoming, found that between 1989 and 2010, the green-up period has been compressed by 40 percent, or by about 27 days over the past 21 years. At the same time, July temperatures, which used to average about 66 degrees, have increased 8 degrees since 1989, which coincides with times of drought and reduced snowpack.

This shortening of the green-up means lower quality food for ungulates such as elk and deer, which have an appetite for and receive the most nutritional benefit from plants when they first start to emerge. As the summer continues, the plants tend to lose some of their nutrition and appeal. The shorter season gives ungulates less time to build the necessary fat reserves that get them through harsh winters. Additionally, it may help to explain why elk numbers are sagging in the area, says Arthur Middleton, a Ph.D. student based in the Cooperative Fish and Wildlife Research Unit at the University of Wyoming and coordinator of the Absaroka Elk Ecology Project.

EDIT

http://www.newwest.net/topic/article/yellowstone_elk_study_points_to_lasting_effects_of_a_hotter_longer_summer/C41/L41/