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Modeling wolf-moose forest interactions at Isle Royale National Park

Photo of Figure 1. Isle Royale National Park (upper left) is home to populations of wolves and moose (upper right, data from Vucetich and Peterson 2015). Simulated trends (+/- 90 percent confidence intervals) in moose population density (lower left), and available forage biomass/moose carrying capacity (lower right) for the three predation scenarios. Actual moose population estimates for Isle Royale from 2006-2015 (black) are provided for reference.
Figure 2. Simulated changes in forest types at Isle Royale after 100 years of no predation vs strong predation rates.
Figure 1. Isle Royale National Park (upper left) is home to populations of wolves and moose (upper right, data from Vucetich and Peterson 2015). Simulated trends (+/- 90 percent confidence intervals) in moose population density (lower left), and available forage biomass/moose carrying capacity (lower right) for the three predation scenarios. Actual moose population estimates for Isle Royale from 2006-2015 (black) are provided for reference. Figure 2. Simulated changes in forest types at Isle Royale after 100 years of no predation vs strong predation rates. Snapshot : The loss of top predators may have unintended consequences for forest composition and function. Forest Service scientists partnered with the U.S. Geologic Survey and National Park Service to investigate the effects of alternative wolf predation scenarios on the moose and forest dynamics at Isle Royale National Park near Michigan’s border with Canada. Will the impending loss of wolves from the park affect the future state of the forest ecosystem?

Principal Investigators(s) :
Sturtevant, Brian R.Miranda, Brian R.
Research Location : Isle Royale National Park
Research Station : Northern Research Station (NRS)
Year : 2017
Highlight ID : 1252

Summary

Loss of top predators may induce a “trophic cascade” within forested ecosystems by releasing browsing ungulate populations that may in turn impact future forest dynamics. Forest Service scientists and their research partners applied a landscape disturbance and succession model (LANDIS-II) to investigate how the moose population could interact with the forest ecosystem of Isle Royale National Park in Michigan over the next century under three different wolf predation scenarios: no predation, weak (long-term average predation rates), and strong (higher than average rates). Increasing predation rates led to lower peak moose population densities, lower biomass removal rates, and higher estimates of forage availability and landscape carrying capacity, especially during the first 40 years in the simulations. Thereafter, moose population density was similar for all predation scenarios, but available forage, moose carrying capacity, and forest composition continued to diverge among predation scenarios. High browsing rates led to reductions in aspen, birch, and balsam fir, and increases in white and black spruce, especially after the simulation year 2050, when existing aspen-birch stands at Isle Royale are projected to naturally decline. The research results support the concept of a trophic cascade in this system, and can help inform alternative predator management strategies as they may affect ungulate populations and forest succession.

Forest Service Partners

External Partners

 
  • National Park Service
  • U.S. Geological Survey

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