Forest Refugia

Forest Refugia

 
 

Warmer temperatures, changing drought patterns, increasing pressure from pests and pathogens, and altered fire regimes associated with climate change, threaten many important natural and cultural resources in the northwestern U.S. However, not all places on the landscape are changing in the same way. Climate change refugia are areas relatively buffered from contemporary climate change over time that enable persistence of valued physical, ecological, and socio-cultural resources (Morelli et al. 2016). Across the Northwest, many different types of refugia are being defined, mapped, and evaluated. These diverse approaches to studying refugia provide the scientific foundation for meeting regional management needs such as preserving old-growth forests, protecting high priority species (e.g., marbled murrelet), and conserving the threatened whitebark pine ecosystem. Here we highlight recent climate change refugia research efforts and discuss their importance to developing a regional climate change adaptation strategy.

  Iconic white bark pine trees are keystone species in high elevation forests, providing critical habitat for wildlife.

Iconic white bark pine trees are keystone species in high elevation forests, providing critical habitat for wildlife.

Refugia may promote conservation of whitebark pine forests

Of all Northwest forests, whitebark pine (Pinus albicaulis)-dominated forests are one of the most threatened due to interactions between white pine blister rust (Cronartium ribicola), bark beetles, drought, changing fire regimes, and climate change. Scientists at the US Forest Service and University of Idaho have developed new methods for mapping “genetic refugia” in whitebark pine forests. By using spatial datasets of white pine blister rust resistance, drought tolerance, late winter cold hardiness, and genetic diversity, they are able to identify populations with favorable genetic attributes that are more likely to persist despite changing environmental conditions. The areas, identified as genetic refugia, are priorities for active conservation and restoration efforts. However, only 1% of the mapped refugia currently exist in protected wilderness areas.

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Fire refugia are integral to fire management in Northwest forests

With an average of 4,100 wildfires burning nearly 758,000 acres annually, fire is a common element of the Northwest landscape. In every fire, there are islands of vegetation that remain unburned or burn at a lower severity—i.e., fire refugia. These fire refugia serve as important resources in the post- fire forest environment. Scientists at the University of Idaho have employed remote-sensing techniques to identify unburned islands by examining 2300 fires occurring between 1984 - 2014 in the interior Northwest. New research at Oregon State University has resulted models predicting fire refugia by classifying areas  dependant on their fire weather conditions and topographic complexity.These new models suggest that many fire refugia are created by area of a landscape that endure through repeated fire events and assist in the development and maintenance of forest ecosystems, including old-growth. However, current fire management aiming to reduce diversity in burn severity may be altering or removing fire refugia needed for the establishment, persistence, and movement of organisms. Identification and management of fire refugia needs to be an integral part of maintaining ecosystem resilience to future fire conditions.

 
  Researchers at OSU have developed a conceptual and modeling framework for predicting refugia as a function of these persistent landscape features. (Krawchuk et al. 2016)

Researchers at OSU have developed a conceptual and modeling framework for predicting refugia as a function of these persistent landscape features. (Krawchuk et al. 2016)

 

Hydrologic refugia buffer Northwest forests from intensifying disturbances

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As with other types of refugia, wetter microenvironments that maintain relatively high water availability—i.e., hydrologic refugia—may help species persist in the face of changing climate conditions. Hydrologic refugia may be especially important at buffering forest species from interacting disturbances like drought and insect outbreaks. USGS and University of Washington researchers are developing new methods of identifying hydrologic refugia. These methods have recently been applied to identify potential refugia in dry mixed-conifer forests in southern Oregon by studying recent drought events in the region. The persistent landscape features that create hydrologic refugia, allow their continued functioning in the face of climate change. Therefore, their identification and management is an important strategy for conserving old-growth forests and other high priority forest resources.

  Preliminary identification of refugia from drought and mountain pine beetle mortality in the Gearhart Mountain Wilderness in southern Oregon in 2009. Refugia were identified using a novel remote sensing approach based on the Normalized Difference Moisture Index.

Preliminary identification of refugia from drought and mountain pine beetle mortality in the Gearhart Mountain Wilderness in southern Oregon in 2009. Refugia were identified using a novel remote sensing approach based on the Normalized Difference Moisture Index.

Refugia are complex, connected landscapes

The Nature Conservancy (TNC) is taking a different approach to mapping climate change refugia in the Northwest. By focusing on two persistent landscape factors —topoclimate diversity and connectedness of the landscape —TNC has developed maps of areas that are likely to be resilient to climate change (Buttrick et al. 2015). These resilient landscapes maps are available for the entire Northwest region and offer a starting place for developing adaptation strategies and guiding future conservation investments in the face of uncertain future conditions.

Refugia as a regional climate adaptation strategy

The research presented here is an important part of developing a regional climate adaptation strategy that manages climate change refugia in order to encourage persistence of valued ecological and sociocultural resources. Managers and scientists can work together to identify and prioritize refugial areas in Northwest forests. Such a strategy can allow managers to focus efforts and limited resources on areas that are likely to provide the largest return on investment. To encourage this, the Northwest Climate Science Center has created the Refugia Research Coalition (RRC). The RRC is an interdisciplinary working group of regional managers and scientists that aims to synthesize new refugia research, create opportunities for the co-production of new, actionable science, and build partnerships that encourage the translation science into management decisions. These efforts will provide a foundation for incorporating refugia research into a regional climate adaptation strategy

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A framework for integrating refugia into a climate change adaptation approach (adapted from Morelli et al. 2017).