Building resilience: Vulnerabilities and adaptation strategies for national forests in southern California
A new bridge over Trabuco Creek in the Cleveland National Forest designed to withstand flooding and debris flows.
By Cristina Winters
On a hot summer weekend in southern California, it seems every city-dweller is looking for a cool escape to the mountains or water. Higher elevations offer cool breezes and fresh air, and going for a dip can provide an immediate break from the heat. Although these natural areas provide important relief from urban heat and opportunities for recreation, future hazards may threaten the infrastructure that makes these trips possible.
The Forest Service, which manages many of the most popular recreation sites in southern California, is working to preserve and enhance public benefit by integrating the best available scientific understanding of various risks to recreation and recreation sites into management. Researchers from the Forest Service’s Pacific Northwest and Pacific Southwest Research Stations and Western Wildland Environmental Threat Assessment Center worked with an interdisciplinary team of resource specialists, recreation managers, and engineers with the Forest Service’s Pacific Southwest Region to assess potential risks to visitors’ outdoor experiences and determine actions to address those risks.
Change in risk to recreation
The assessment focused on the Angeles, Los Padres, San Bernardino, and Cleveland National Forests as well as the Santa Monica Mountains National Recreation Area. Popular and regionally iconic sites such as the Mount Wilson Observatory, San Gorgonio Mountain (the highest peak in southern California), and the Big Sur coast are within these areas. These popular sites offer quick escapes from the summer heat and are predicted to become even more popular in the future.
As areas become more popular and temperatures increase, there are increased risks. Researchers are concerned about more instances of heat illness, poison oak spread, tick-borne diseases, and harmful algae blooms in lakes and streams. Campgrounds and trailheads near streams may also be vulnerable to flooding and landslides. Decreased availability of fresh water sources along backpacking trails, more air pollution, and smoke from wildfire are among the drawbacks that may override the traditional benefits associated with spending time outside.
Although warm-weather activities comprise most of the recreation in the southern California assessment area, the future of winter activities is also uncertain because of changes in temperature and precipitation. More precipitation is falling as rain instead of snow at higher elevations, threatening the skiing and snowboarding season. Increased droughts may limit the amount of any form of precipitation some years. Shorter winter seasons will change the economic reality in popular areas like the Big Bear Mountain resorts in the San Bernardino National Forest and Mountain High Resort in the Angeles National Forest.
Burdens on recreation infrastructure
Extreme precipitation events can damage roads and other structures. More frequent atmospheric rivers stress critical drainage features and may cause them to fail, devastating roads and trails. Extreme precipitation events are expected to increase under future climate conditions, and years of deferred maintenance contribute to a higher risk of infrastructure failure.
Understanding the potential effects of these changes allows recreation managers and engineers to better prepare recreation sites to withstand extreme weather events. For example, managers can use insights about expected changes to hydrology and flood regimes over the coming decades to design more resilient roads and bridges.
Learn more about how climate-induced events are expected to affect recreation, infrastructure, and ecosystem services in this new publication, Vulnerability of recreation, infrastructure, and ecosystem services to climate change in southern California.