Assessing the vulnerability and conservation potential of old growth forests in British Columbia, Canada.

Description

Abstract

Climate change is predicted to have widespread effects on the distribution of many species and ecosystems, including old growth forests. Because of the slow development time of old growth forests, it is especially important for their management to map and understand areas of relative climatic stability, or “climate-change refugia”. British Columbia (BC), Canada, holds globally significant areas of old growth forests with varying levels of climate change threat. To better understand these threats, we used Maxent to model climate niches of BC’s ecosystem types, as represented by Biogeoclimatic Ecosystem Classification units. We then projected ecosystem changes for the 2050s climate period and overlaid them with current and potential future old growth forests (old forests projected to become old growth in absence of fire) to identify where these forests are likely to persist (“old growth refugia) and develop a Provincial Refugia Probability Index. Finally, we assessed to what extent BC’s current protected areas network represents current and future old growth forest. Our analysis identified 110,545 km² of current old growth in BC, which has the potential to increase via natural succession by up to an additional 69,410 km² by 2055, barring future wildfires or other disturbances. We also showed that up to 54% of the province and 63% of current old growth fell within the projected area of maximum total refugia for the 2050s climate period. Less than 12% of these forests were within refugia and already conserved, with <0.2% protected in areas with “high” probability of refugia. Thus, we demonstrate that almost all old growth in BC is susceptible to climate change, human development, or both, highlighting the continued vulnerability of these forests into the middle of the century. Overall, over 51% of BC’s old growth was identified as susceptible to human development and within the projected area of maximum total refugia. We suggest future planning to focus on conserving elements of these areas, as their projected climate stability potentially translates into efficient, long-term protections. We provide a framework for forest and conservation managers to assess the future effects of climate change on old growth forests in BC, or beyond.