Introduction
We don’t know exactly how climate change will affect Oregon’s forests. Scientists are confident that temperatures will continue to rise, but the outlook for precipitation is less clear. Taken alone, we know warmer temperatures will reduce snowpack, decrease summer streamflow, and increase water loss from trees and other plants.
Overall, climate change is leading to more frequent, larger, and more severe droughts and wildfires across the Western United States. These changes will affect how forests grow, develop and respond to disturbance. However, the speed and extent of climate change are uncertain, and we don’t know precisely how forests will respond. Thus, climate change makes long-range planning particularly challenging for today’s forest landowners.
This series on managing forests in a changing climate takes a broad look at the topic, examining when change may occur and how we can manage forests to cope with it. In this fact sheet, we start with a big-picture view, providing a conceptual framework that details two potential strategies:
- Mitigation and adaptation
- Resist-accept-direct
Mitigation and adaptation
The United Nations Intergovernmental Panel on Climate Change describes two main strategies to limit climate change and its effects:
- Mitigation involves human intervention to a) reduce greenhouse gas emissions, and b) enhance the ability of natural systems to absorb and store greenhouse gases. Forest managers might use longer rotations that help remove carbon dioxide from the atmosphere, for example.
- Adaptation is the adjustment by humans to actual or expected changes in climate and their effects. For example, people can help forests cope by changing species composition, reducing forest density, using assisted migration or pursuing other activities that enhance resistance or resilience to disturbance.
Resist-accept-direct
Land managers may utilize resist, accept, or direct strategies to help forests cope with climate change:
- Resist — Forests can be managed to withstand the impacts of climate change, such as increasing their resistance to drought or wildfire. Alternatively, managers can enhance forest resilience, which is the capacity to return to pre-existing conditions after a disturbance. The goal is to minimize long-term changes to the forest.
- Accept — Foresters might allow forests to transition to new conditions, if they still meet landowner objectives. Transition refers to a directional change in forest conditions. If allowed to happen naturally, this would be an “accept” strategy.
- Direct — Foresters might guide how forests respond to climate change. If forest management activities are intentionally used to promote transition to new desired forest conditions, this would be considered a “direct” strategy.
This fact sheet focuses on the resist-accept-direct, or RAD, approach to managing forest ecosystems. Other fact sheets in this series provide more examples of the RAD approach in Oregon forests.
Resist
- Maintain forest structure and composition that is resistant or resilient to wildfire, drought, insects, diseases or the loss of biodiversity.
- Potential activities include using thinning to alter stand structure or using prescribed fire to reduce surface and ladder fuels.
- Resistance is mostly viable as a short-term strategy (10–30 years) to conserve existing forests and associated natural resources. In contrast, landowners may need to adopt other strategies to meet their objectives over the long term.
Accept
- Allow forests to change in response to increases in temperatures and changes in precipitation, particularly at the margins of forest types or species distributions. These changes might include transitions from:
- Dry forest, woodland or savanna to grass-dominated or shrub-dominated ecosystems.
- Pine to juniper or sagebrush steppe.
- Dry mixed-conifer to pine woodland.
- Moist mixed-conifer to dry mixed-conifer.
- Allow conifer regeneration at upper elevations and movement of conifers above the historical treeline.
- Potential management actions include monitoring to ensure that changes in forest conditions promote adaptation to climate change and continue to meet objectives.
Direct
- Assist the transition to new forest conditions (for example, stand structure and species composition) that are better able to cope with future climates (Figure 3). Activities that may facilitate desirable changes include:
- Replacing Douglas-fir forests on the dry margins of the Willamette Valley with Oregon white oak, Willamette Valley ponderosa pine, or a mixture of oak and pine stands.
- Transitioning forestland to novel grassland or shrub-dominated ecosystems.
- Planting new species to achieve species-level and population-level assisted migration.
- Thinning stands or planting to promote the conversion of forests to species that are more resistant to wildfire, drought, insects and disease.
Climate change and forest ecosystem services over time
Figure 3. Change can occur abruptly or gradually. The actions you take as a manager can impact the rate of change.
Summary
Landowners can do many things to prepare their forests for climate change. A good start is to assess where your property sits along temperature and moisture gradients, categorize the forest types you have and learn expectations for climate change in your region.
Are you already seeing increased tree mortality or wildfire on your property? Given the uncertainties of climate change, the RAD framework can help guide your management activities in the near and distant future. Whatever course you choose, it’s important to monitor the changes in your forest and adapt accordingly.
Resources
U.S. Department of Agriculture Northwest Climate Hub
Climate Adaptation Frameworks: RAD and RRT
Vulnerability assessments for forests in Oregon and elsewhere
Reference
Millar, Constance I., and Nathan L. Stephenson. 2015. Temperate forest health in an era of emerging megadisturbance. Science, Volume 349, Issue 6250: 823-826.
About the authors
