After a more than a century of fighting to keep fire out of forests, reintroducing it is now an important management goal. Yet changes over the past century have left prescribed burning with a big job to do. Development, wildfire suppression, rising global temperatures, extended droughts, exotic species invasions, and longer fire seasons add complexity to using this practice.
Managers must consider how often, how intensely, and what time of year to burn; for insights they often look to how and when fires burned historically. However, attempting to mimic historical wildfires that burned in hot, dry conditions is risky. Burning in fall or spring when temperature and humidity are low reduces the risk of prescribed fires becoming uncontrollable, but does it have the intended effects? How do forest ecosystems that historically were adapted to fire respond when fire is reintroduced after so much time without it?
Forest Service researchers Becky Kerns and Michelle Day conducted a long-term experiment in the Malheur National Forest, Oregon, to assess how season and time between prescribed burns affect understory plant communities in ponderosa pine forests. They found that some native plants persisted and recovered from fire but didn’t respond vigorously, while invasive species tended to spread. These findings may help forest managers design more effective prescribed-fire treatments and avoid unintended consequences.
The last 50 years or so have seen a steady increase in the rate of destructive wildfires across the world, partly as a result of climate change and partly as a result of encroachment of human settlement on fire-based ecosystems (Russell et al. 2004; Westerling et al. 2006). Years of active fire suppression in such areas has inevitably led to the build-up of hazardous fuel loads, creating ideal conditions for destructive wildfires (Johnson et al. 2001). Recently, serious wildfires have occurred in Australia, southeast Asia and the Mediterranean, as well as those occurring in the USA in California, Montana, Idaho and Alaska. Current thinking on fire management is very much focused on re-instating natural fire regimes and allowing fire, as nearly as possible, to function in its natural ecological role (Miller 2006), thereby reducing the occurrence of destructive fires. Mechanical fuel treatments (e.g. thinning) and prescribed burning are being used to reduce fuel loads to near natural conditions, after which natural fire regimes can be allowed to operate. There are two main types of thinning that either remove selected trees to create a more widely spaced forest consisting of trees of different sizes/ages or remove all smaller trees and brush within the understory to leave a more uniform forest of more widely spaced older trees. Prescribed burning uses small managed fires, rather than mechanical means, to achieve the latter. This is a long and involved process and often has the potential to create conflict between the different management regimes associated with adjacent lands and between the different inhabitants and stakeholders affected in the short to medium term. This requires a high degree of collaboration and participatory planning if acceptable fuel reduction strategies and management plans are to be developed.
The Fire Severity Mapping System (FIRESEV) project is an effort to provide critical information and tools to fire managers that enhance their ability to assess potential ecological effects of wildland fire. A major component of FIRESEV is the development of a Severe Fire Potential Map (SFPM), a geographic dataset covering the contiguous United States (CONUS) that quantifies the potential for wildland fires to burn with higher severity should they occur (Dillon et al 2011a). We developed this map using empirical observations and statistical models to relate biophysical conditions at the time and location of a fire to the resulting severity. For our purposes, burn severity refers to the degree to which aboveground biomass has been altered as expressed in the change between pre- and post-fire satellite imagery (Lentile et al 2006). Our aim in creating the SFPM is to explore the relationships between site characteristics and burn severity (Dillon et al 2011b) and to provide land managers with a tool that can forecast the potential severity of future fires.
Surface fuels data are of critical importance for supporting fire incident management, risk assessment, and fuel management planning, but the development of surface fuels data can be expensive and time consuming. The data development process is extensive, generally beginning with acquisition of remotely sensed spatial data such as aerial photography or satellite imagery (Keane and others 2001). The spatial vegetation data are then crosswalked to a set of fire behavior fuel models that describe the available fuels (the burnable portions of the vegetation) (Anderson 1982, Scott and Burgan 2005). Finally, spatial fuels data are used as input to tools such as FARSITE and FlamMap to model current and potential fire spread and behavior (Finney 1998, Finney 2006).
Land management agencies need to understand and monitor the consequences of their fire suppression decisions. We developed a framework for retrospective fire behavior modeling and impact assessment to determine where ignitions would have spread had they not been suppressed and to assess the cumulative effects that would have resulted. This document is a general guidebook for applying this methodology and is for land managers interested in quantifying the impacts of fire suppression. Using this methodology will help land managers track the cumulative effects of suppression, frame future suppression decisions and costbenefit analyses in the context of past experiences, and communicate tradeoffs to the public, non-government organizations, land management agencies, and other interested parties.
Adult salmon sense when the time is right to leave the ocean and head for fresh water to spawn. But how do they know this? And how will climate change affect this cycle? Rebecca Flitcroft, a research fish biologist with the USDA Forest Service, Pacific Northwest Research Station, and colleagues took a closer look at the connection between migration patterns and stream conditions.
They found that water temperature and the rate of streamflow appear to be two of the environmental conditions that precipitate the migration of salmon to their freshwater spawning grounds. This doesn’t bode well for salmon, given that these stream conditions are being altered by climate change.
The researchers used hydrologic data collected at dams in Oregon and Washington and linked them with data showing the timing of migratory fish passing those dams. The findings are displayed visually in ichthyographs, a newly developed graphic tool that shows the precise conditions under which fish move upstream.
This research provides a current baseline for understanding the connection between hydrologic conditions and fish movement. It also highlights ways in which the effects of climate change potentially could be mitigated by managing streamflows at critical times of the year to benefit salmon migration.