Which tree species and biome types are most vulnerable to climate change in the US Northern Rocky Mountains?

Andrew J Hansen,Linda B Phillips

doi:10.1016/j.foreco.2014.11.008

Abstract

The goal of this study was to assess components of vulnerability of tree species and biome types to projected future climate within the Great Northern Landscape Conservation Cooperative (GNLCC) in the US Northern Rockies and the ecosystems surrounding Glacier and Yellowstone/Grand Teton National Parks. We drew on the results of five published studies and analyzed current and projected future climate suitability for 11 tree species and 8 biome types under two IPCC emissions scenarios. We assessed components of vulnerability based on four metrics of current and projected future climate suitability. Results for biome types indicated largely a shift from climates suitable for alpine and subalpine conifer to climates suitable for desert scrub and grassland types. Results from the four studies of tree species indicated substantial loss of area of climate suitability for the four subalpine species by 2100. This was especially true for Whitebark pine (Pinus albicaulis). Suitable climate for this species dropped from just over 20% of the study area in the reference period to 0.5–7.0% by 2070–2100 under the A2 scenario. The studies agreed in projecting expansion of climate suitability for some montane tree species but disagreed on expansion of climate suitability of west-side mesic tree species to eastside locations such as Yellowstone National park. Importantly, the rankings of tree species vulnerability were similar among studies, scenarios, and geographic areas and indicated highest vulnerability for Whitebark pine and Mountain hemlock (Tsuga mertensiana). The results should help federal managers in the GNLCC prioritize tree species for climate adaptation strategies. Moreover, our methods for using published data as a basis for climate vulnerability assessment can be applied within other LCCs across the US and other management units internationally.

Highlights

Federal land managers are increasingly concerned about how climate change affects natural resources and ecosystem services within their jurisdictions
The projected biome shifts in Greater Yellowstone were more extreme that for Great Northern Landscape Conservation Cooperative (GNLCC) with conifer forest types dropping from 82% of the area to 26% and scrub types increasing from 0% to 48% of the area
As a component of the climate adaptation planning framework adapted by the US Department of Interior (DOI) (Glick et al, 2011; Stein et al, 2014), the results of this study can serve as measures of potential impact of climate change on tree species and biome types

Summary

Introduction

Federal land managers are increasingly concerned about how climate change affects natural resources and ecosystem services within their jurisdictions. Climate warming and drying have been pronounced within western states, resulting in increased frequency of severe fires, widespread forest pest outbreaks, and drought-induced forest mortality (Westerling et al, 2006; Allen et al, 2010). These factors in combination have led to large scale forest die-off especially in the southwestern deserts, the Rocky Mountains, and the Sierra Nevada (Breshears et al, 2005) and include keystone tree species such as Whitebark pine (Pinus albicaulis) ( Logan et al, 2010) and Joshua tree (Yucca brevifolia) ( Cole et al, 2011). Understanding forest response to climate change within local and regional management jurisdic-tions is vital to designing locally relevant strategies to cope with pending changes

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Conclusion