Projected Thermal Habitat Impacts to Brook Trout from Land Use and Climate Change in the Kezar Lake Watershed, Maine

In the Northeast, intact stream populations of brook trout (Salvelinus fontinalis) exist in only approximately 5 percent of subwatersheds. Some of the last remaining, native, wild and intact populations of brook trout exist in northern and western Maine in headwater streams. Over the next several decades, air temperatures in the Northeast are projected to increase between 0.8 to 1.7°C in the summer from climate change. Based on a regression between paired air and stream temperatures in the White Mountain National Forest (WMNF), this could result in an increase of 1.0 to 2.2°C for instream temperatures over the same time period. Forest harvesting and headwater stream buffer treatments in western Maine have resulted in observed increases in stream temperatures ranging between 1.0 and 4.4°C for buffer widths ranging between 0 and 36 feet. Annual in-stream monitoring was conducted in a tributary of Kezar Lake that contains brook trout. Based on a synthesis of available temperature tolerance metrics for brook trout, projected temperature increases, and planned timber harvests adjacent to headwater streams, we analyzed instream temperatures and identified areas of concern for potential thermal impacts to brook trout within the watershed from land use and climate change.