Introduction: Climate Change in the Mountains of Maine and the Northeast

Mountains in the Northeast are critical for maintaining biodiversity, recreational opportunities, and freshwater resources, and as potential refugia for cold-dependent flora and fauna. The mountain regions of Maine, the rest of northern New England and New York’s Adirondacks, and eastern Canada (Fig. 1) are within a day’s drive of the largest metropolitan areas in the US and Canada, yet are recognized as being largely unfragmented and intact. Many mountain ecosystems are protected from local pressures such as human development, agriculture, and other anthropogenic change via conservation efforts or de facto due to inaccessible terrain, but other stressors such as climate change are affecting these fragile and unique systems. The northeastern US is warming faster than most other regions of the world, and these trends are projected to continue (Karmalkar and Bradley 2018). Although detailed data are lacking from Maine’s mountains, research has shown that midto high-elevation areas, as well as more northerly regions, are experiencing the largest climate changes (Pepin et al. 2015). These changes are affecting biodiversity and ecosystem services at all levels (Weiskopf et al. 2020). Thus, mountain ecosystems are of great interest for scientific research that tests hypotheses about species interactions, landscape ecology, physical processes (hydrology, geochemistry), climate-change refugia and tipping points, and physiological response of biota in an extreme environment. These issues were explored in several regional events over the past 5 decades. On April 29, 1972, the first Maine Mountain Conference convened in Augusta, ME, “for the purpose of discussing the nature of the Maine mountain environment and also the present and future uses of these areas” (Maine Mountain Committee 1972).