Forest ThreatNet

By Stephanie Worley Firley, EFETAC

In forests as in life, the only constant is change. Forest species are ever adjusting to changing conditions resulting from seasonal fluctuations in temperature and precipitation, disturbances like storms and wildfire, and interactions with other species. But typical temperature and precipitation patterns are now also changing; in some areas, changes are occurring rather rapidly. Many tree populations may be hard pressed to survive given the rate of climatic change. Whether tree populations adapt on site to changing habitat conditions, shift their ranges to new suitable locations, or simply die out, the forests we know today—and the genetic makeup of the species within them—could be very different by the middle of the 21st century. Now, researchers are asking the question: in a future with a different climate, where might the trees be?

With support from the USDA Forest Service Forest Health Monitoring program, EFETAC ecologist Bill Hargrove and North Carolina State University cooperating scientists Kevin Potter and Frank Koch are collaborating to develop Forecasts of Climate-Associated Shifts in Tree Species, or ForeCASTS. Using projections of future climate in combination with the concept of fine-scale ecoregions—land areas that share similar environmental characteristics, such as soils, topography, and climate variables—the researchers are developing maps depicting future suitable habitat ranges for North American tree species within the United States as well as across the globe. The maps can help scientists, land managers, and policy makers target tree species for monitoring, conservation, and management activities by pinpointing locations where climate change pressures are likely to be most intense. “The Forest Service has a long history of understanding that the seed source makes a huge difference in tree growth and performance, so the ForeCASTS maps can ultimately be used to assess the risk to genetic integrity of North American forest tree populations,” explains Hargrove.

Above: A ForeCASTS map shows the “minimum required movement” for northern red oak (Quercus rubra) to new suitable habitat under a lower greenhouse gas emissions climate scenario in 2050. Yellow areas are currently suitable and expected to be suitable in the future; green areas are expected to become suitable in the future; and red areas are currently suitable habitat areas expected to become unsuitable.

So far, maps have been developed for 213 tree species under varying climate models and scenarios for the years 2050 and 2100, including “minimum required movement” maps that quantify the distances between current habitat locations that may be unsuitable in the future and new suitable habitat ranges. “The general trend, as we would expect, is for tree ranges to expand at least a little bit to the north, and to drop off at least a little bit at their southern edges. Looking at species with ranges that include the Southern Appalachians, the ForeCASTS maps show nearly all species decreasing their overall suitable habitat area,” says Potter.

The ForeCASTS maps are still provisional. As the project unfolds, the researchers are refining the available map products and adding additional species to the queue. They plan to identify closest “lifeboat” areas for tree species that may migrate from multiple locations as well as add measures of performance to determine where species may thrive in future projected habitat ranges. Later, the methods used in ForeCASTS could be employed to explore future distributions of invasive species. Visit http://www.forestthreats.org/tools/ForeCASTS to learn more.


ForGRAS: Ranking Tree Species at Risk in the Southern Appalachians

Forest management and genetic conservation strategies must be as complex and diverse as tree species’ responses to threats like climate change and insect and disease infestation.

To help land managers and policy makers focus planning activities and thus make the most effective use of limited resources, Kevin Potter and Barbara Crane, Forest Service Southern Region regional geneticist, developed the Forest Tree Genetic Risk Assessment System (ForGRAS), a tool for ranking tree species’ relative risk of genetic degradation. ForGRAS considers ecological and life history traits, species-specific projections of climate change pressure, and predictions of pest and pathogen susceptibility for 131 native Southern Appalachian tree species.

The ForGRAS framework can account for multiple threats to forest health that may cause the most severe genetic impacts, and is flexible enough to be applied at multiple scales and areas where appropriate data exist for the species of interest. In fact, it is also being used in genetic risk assessments in the Pacific Northwest. Contact Potter at kevin.potter@usda.gov for more information.