watervulnerability

Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10)
• Restoring riparian vegetation to maintain cooler water temperatures.
There are many other tasks, but the underlying theme is that fixing existing problems can go a long way
toward mitigating climate change effects. However, to be most effective, the current engineering or
biological standards should also be reviewed and adjusted in view of the predicted changes.
One other area where managers can be effective is through reviews of their Forest Plans. As an example,
one of the biggest issues in the past, for the Chugach National Forest, has been winter recreational use.
The Plan is up for review and managers might consider the possibility of reduced recreational
opportunities from shorter winters and higher snowlines. There may be a need to open new winter
recreation areas, rewrite management prescriptions for existing uses, or improve access to higher
elevation areas.
If managers wish to be proactive about climate change, a committee could look at each component of the
Forest Plan to see how it might be affected by predicted changes. Some areas may need little or no
adjustment, and monitoring baseline conditions might be sufficient. The Chugach plan has a Monitoring
and Evaluation Strategy, which would be the best place to establish a climate-change monitoring design.
In any case, the Forest Plan is one place where managers can establish policy and show commitment
toward addressing climate change.
Biological Issues
The biggest lingering question is how species, particularly the highly valued salmon species, will respond
to climate changes. Unlike areas in the lower 48 states, the freshwater changes in coastal Alaska are less
likely to have direct lethal effects to salmonids, but life-cycle timing and changes to food source species
could occur. Although Haufler et al. (2010) state that a risk assessment needs to be made for Alaska
salmon, knowing how salmon will respond to the predicted changes and trying to assign risk appear to be
difficult tasks at this point.
As mentioned in the Eyak Lake watershed discussion, part of the salmon response will depend on the
response of other organisms, especially whether the life cycles of prey species change in synchrony with
newly emerged fry. This is not presently known. The other part of this situation is how well a species
itself can adapt to changing conditions. If, for example, warmer temperatures cause fry to hatch too early
in the spring, does the species have the innate capacity to adjust its spawning to a time later in the fall to
compensate?
It would appear that this capacity does exist for some salmon species that have a diverse life history. One
example is a groundwater-fed spawning channel near Cordova used by coho salmon. The adults spawn
over a wide period of time, from October well into December, with fry emerging from May to mid-July
(unpublished Forest Service data). If warmer groundwater temperatures cause faster development, but the
optimal hatching time continues to be in June, the progeny of late-December spawners could still sustain
the run and adapt over time. Such diversity may make these species more resilient to change, assuming
that food chains or other conditions are not totally disrupted by climate change.
Another part of this question is how well species will survive climate changes, given the highly variable
weather conditions that already exist in an area like Cordova. From 1949 to 2004, the mean annual
temperature at the Cordova airport has been 39.1 °F, but the extreme annual temperatures have ranged
from 34.3 to 41.4 °F. Annual precipitation has averaged 96 inches, but has ranged from 54 to 139 inches.
There is no certainty that species will be able to cope with extended years of the predicted higher
temperatures and precipitation, but the species of the area have survived conditions similar to what is
296 Assessing the Vulnerability of Watersheds to Climate Change