While protected areas generally have stable geographic boundaries, conditions within them change reflecting shifts in land use, species invasions, altered disturbance regimes, and climate change. Climate change has emerged as a serious threat to United States National Parks. Climatic conditions in these parks are already beyond their historic range of variability and plants in 76% of U.S. parks are experiencing earlier onsets of phenological events like leaf-out and first-flowering. In the Great Lakes Region, temperatures will likely increase an additional 3-5 °C over the next century, straining the ability of many plant species to cope with such rapid climate change. Our primary goal was to project the extent to which habitat suitability for understory flora in the nine national parks of the Great Lakes Inventory and Monitoring Network will be affected by climate change. To do so, we first used boosted regression tree models to fit current distributions of the 30 most common understory species in these parks using data on climates, soils, and topographic variables. We then used these models to predict how climatic suitability for these species will likely change by the year 2085, by projecting future climates using two emissions scenarios and four global circulation models.
Results/Conclusions
Climatic changes in the nine Great Lakes national parks are occurring at a rapid pace, with climate velocity between 4.5 and 13.1 km/year under RCP 8.5. Our projections indicate that climatic niches currently present in national parks may shift well beyond park boundaries by 2085, a situation that could lead to dramatic changes in the distributions of the 30 most abundant species in the Great Lakes national parks. Species with northern distributions in our region may decline drastically across most parks, while probabilities of occurrence for many southern species may increase. For instance, Clintonia borealis (bluebead lily) could lose 90-100% of its climatically suitable habitat in these national parks by 2085. In contrast, the more southerly species, Arisaema triphyllum (Jack-in-the-pulpit), is projected to gain suitable habitats in northern parks. The rapidity of predicted climate change in this region will likely challenge the ability of many cool-adapted and currently common understory species to persist in these parks. Park managers can integrate these results into existing climate adaptation plans as they seek to resist, accommodate, or direct the changes resulting from future climate change.