Are U.S. national parks in the Upper Midwest acting as refugia? Inside vs. outside park disturbance regimes

Abstract

AbstractLandscape disturbances such as forest harvest, blowdowns, fire, and development activities create patches on the landscape that modify the structure and integrity of ecosystems. Understanding the agents of change, where they occur, and how much of the landscape they are affecting will assist resource managers in making difficult decisions. To fulfill this goal, the National Park Service implemented a long‐term monitoring program to quantify landscape dynamics across 1.5 million ha within and adjacent to eight national parks in the Upper Midwest United States using an automated satellite‐based change detection program called LandTrendr (Landsat‐based detection of trends in disturbance and recovery). The disturbance agents detected inside parks included beaver, blowdown, development, fire, flooding, insect/disease, and forest harvest. Pictured Rocks National Lakeshore had the largest percentage of area affected inside a park (11.83%, 1.96% per yr), and Isle Royal National Park had the lowest percentage of land affected (0.03%, 0.05% per yr). Tree defoliation due to insect/disease affected the largest percentage of land inside parks (1.56%, or 0.26% per yr) but did not result in tree mortality. Adjacent to parks, disturbance agents detected included agriculture, beaver, blowdown, development, insect/disease, fire, flooding, and forest harvest. Lands adjacent to Pictured Rocks National Lakeshore experienced the highest rate of disturbance (8.75%, 1.45% per yr), largely due to forest harvests. The lands adjacent to the Mississippi National River and Recreation Area experienced the lowest percentage of change (0.62%, 0.10% per yr), with development activities being responsible for most of the change. Forest harvesting was the major change agent outside six of the eight parks, an indication of how important the wood products industry is in the region and the level to which this region is forested. These national parks are acting as integral buffers from adjacent lands that either do not have the ability or lack the capacity to allow the ecosystem to function without intensive management efforts.