PARENT SESSION
Session #2: Local ecosystem effects of climate change: The interaction between climate, societal decisions, and ecosystems. Organized by: J.S. Baron, D.S. Ojima, N.T. Hobbs, and A.C. Covich.
Monday, August 6, 2001. Madison Ballroom A
Impacts of climate changes on elk population dynamics in Rocky Mountain National Park, Colorado.
HOBBS, N.1, WANG, GUIMING1, SINGER, FRANCIS1, OJIMA, DENNIS1, LUBOW, BRUCE2, 1 2
ABSTRACT- The impacts of global climate change on species will be manifest in changes in the dynamics of populations at local scales. These local impacts are likely to be seen in national parks and conservation areas. We evaluated the strength of evidence for alternative models relating population dynamics of elk to historic weather data in Rocky Mountain National Park (RMNP), Colorado. Using the best approximating population models and projections based on the Hadley and Canadian Climate Center climate models, we examined the potential impact of future climate on the elk population. All models with support in the data revealed density-dependent effects of population size on growth rates. The best-approximating logistic population model suggested that elevated summer precipitation accelerated elk population growth, but summer minimum temperatures slowed growth. The best approximating non-linear matrix model indicated that elevated mean winter minimum temperature enhanced recruitment of juveniles, while elevated summer precipitation enhanced the survival of calves. Warmer winters and wetter summers predicted by the Hadley model would double the equilibrium population size. Warmer winters and drier summers predicted by the Canadian Climate Center model would raise the equilibrium population by about 50%. Managers of national parks have relied on effects of weather to regulate populations of native ungulates to prevent the elk population from overabundance. Our results suggest that these regulating effects may weaken if climate changes occur as widely predicted.
KEY WORDS: model selection, density dependence, climate effects, population dynamics