Climate Change and Herbivores: Forty Years in a Bunchgrass Prairie

Area of Science:

• Ecology
• Climate Change Biology
• Wildlife Management

Background:

• Anthropogenic climate change is expected to alter wild herbivore distribution and abundance due to impacts on forage.
• Species presence/absence is often the primary focus when projecting herbivore responses to climate change.

Purpose of the Study:

• To investigate wild herbivore population dynamics in response to climate-driven vegetation changes.
• To assess if observed herbivore trends align with climate change projections at the National Bison Range.

Main Methods:

• Long-term monitoring (since 1978) of herbivore abundances (grasshoppers, microtine rodents, ungulates) using various census techniques.
• Concurrent measurement of climate data, vegetation quantity (biomass), and forage quality (nitrogen content, chemical solubility).

Main Results:

• Contrary to warming/drying expectations, forage biomass and quality (solubility) increased.
• Herbivore abundance increased by 18%, with grass-dependent species (bison, elk, etc.) increasing, while others declined.
• Grasshopper populations, historically significant consumers, did not increase as predicted, altering trophic dynamics.

Conclusions:

• Wild herbivores exhibit rapid responses to climate-induced vegetation shifts, not solely through range shifts.
• Observed changes indicate a complex alteration of trophic dynamics rather than simple species loss or addition.
• Further research into ecosystem dynamics is crucial for understanding these complex herbivore responses to climate change.