"Some have read this paper and believe that we are discounting the information gained from palaeo-ecological research but we think this is still very important," Scott Stephens of the University of California, Berkeley told environmentalresearchweb. "However, I believe some new ideas should be considered as we move into a novel climate with forests that have many novel stressors such as invasive species, fragmentation, air and water pollution, and land development."
Along with Constance Millar and Brandon Collins of the USDA Forest Service, Stephens has assembled a list of adaptive management options for forests in Mediterranean regions. The team reckons that aiming for species persistence on a broad eco-region scale is the most appropriate goal under climate change, rather than hoping to keep current species ranges constant or populations at their existing levels.
Mediterranean climates – warm, dry summers and cold, wet winters – occur around the Mediterranean Basin, across California, parts of Western and South Australia, south-western South Africa and some of central Chile.
The team studied mixed conifer forest and subalpine and alpine vegetation in the Sierra Nevada mountains of southern California and the Sierra San Pedro Martir mountains in Mexico. The California forests have experienced logging and fire exclusion for roughly the last century, whereas those in Mexico have undergone little harvesting and fire-suppression regimes only since the 1970s.
The researchers found that the Mexican forest was particularly resilient, recovering well from a severe drought from 1999 to 2002, and a wildfire in 2003. They believe that this resilience was because of the heterogenous spatial structure of the forest and surface fuels – a feature that could well be worth replicating in other forests.
Current management practices do not tend to promote such heterogeneity. With this in mind, the team recommends the use of longer burning periods with less intense ignition patterns to boost variability in fire behaviour and effects. At the moment burning windows tend to be a week or less because of air-quality limits.
"The costs of conducting prescribed fires or managing wildland fires from a public health standpoint should be weighed against the benefits of avoiding the exacerbated, and often prolonged effects associated with large and intense wildfires," write the researchers in ERL.
Climate change is predicted to boost the frequency and severity of forest fires so restoring the patterns of burning and forest structure that were in place before fire-exclusion management regimes began should help to boost resilience. It may also be useful to set up refugia for species such as the Sierra Nevada yellow-legged frog (Rana sierrae), which is suffering declines throughout its range, by introducing them to a network of high-elevation lakes from which non-native trout have been removed.
Other measures could include assisting species migrations, creating porous landscapes through which it is easy for species to move, and using more diverse planting mixes.
The researchers stress, however, that the most appropriate solutions will depend on the specific site and conditions. And managers of forests in non-Mediterranean regions that are mainly disturbed by insects, disease or wind-throw, rather than fire, will need to develop a different set of management tools.
"Another idea is the concept of increased uncertainty; we are not going to be able to forecast the future with high precision or accuracy," said Stephens. "This will stress political institutions and other policy makers in ways that are unforeseen at this point."
Stephens hopes that the study could create more critical thinking regarding what forest managers are proposing. "There is no silver bullet in this paper but some [of the] ideas coupled with strong Adaptive Management Programs are probably the best way to move forward," he said.
The researchers reported their work in ERL.