watervulnerability

Chequamegon-­‐Nicolet National Forest Watershed Vulnerability Assessment, Eastern Region (R9)
Changes to predicted available habitat for the five warm water fishes under a moderate warming scenario
vary significantly. Two were predicted to increase by 468 to 973 percent two were predicted to remain
about the same, and one was predicted to decline by 79 percent.
These results indicate that cold and cool water fish on the CNNF are very vulnerable to moderate and
major warming. Such warming could cause large declines in these fish, which could substantially impact
stream ecology throughout the CNNF.
The predicted fish distributions for the current climate and moderate warming were analyzed to determine
the percent change in cold and cool water fish habitat in each HUC-6 on the CNNF. These results were
used to place each watershed into one of four vulnerability classes. The most vulnerable HUC-6s are
those predicted to contain a substantial amount of habitat under the current climate but which also had
substantial declines in predicted habitat with moderate warming. The least vulnerable HUC-6s are
primarily those with little or no predicted habitat given the existing climate.
The increase of 0.8 o C for each 1.0 o C increase in air temperature used by Lyons et al. (2010) in their
study was an oversimplification necessitated by the statewide study that did not take into account how
groundwater input, land uses, or changes in flow might alter the response of streams to air temperature
increases.
Composite Watershed Vulnerability
Watersheds with very low composite vulnerability were exclusively or predominantly groundwater
recharge zones. These were rated very low because they support low densities of the water resource
values (wetlands, stream crossings, cold and cool water stream fisheries). They also contain highly
permeable soils, in which adverse effects to groundwater recharge from climate changes are least likely.
The vulnerability of other watersheds depended on the combined occurrence of wetlands, runoff potential,
road-stream crossing density, and the presence of cold and cool water fisheries. As the occurrence of
these attributes increased, so did overall watershed vulnerability to climate changes.
RECOMMENDATIONS
Wetlands
There is a need to conduct much more comprehensive wetland modeling with downscaled data from
additional GCMs, scenarios, and locations to verify and refine the preliminary results described above.
Modeling should also be conducted for a variety of bogs with different wetland and contributing
watershed areas.
Other wetland types, including vernal ponds, fens, and weak fens, should be modeled and evaluated for
their vulnerability to climate change.
Existing mapping that includes wetland units, such as Wisconsin Wetland Inventory, WISCLAND and
Forest Service stand inventory, is inadequate to fully evaluate the potential impacts of climate change on
wetlands because it does not adequately characterize water source and flow regimes. In addition, this
mapping frequently does not include vernal ponds, does not incorporate watershed divides through
wetlands, and may have inaccuracies due to limited field verification. National Forest ecological land type
inventory mapping provides the most accurate information, but is limited to areas within the National
Forest boundary. Wetland inventories and mapping should be upgraded as soon as to solve these
shortcomings and to allow more accurate determination of wetland vulnerability to climate change.
262 Assessing the Vulnerability of Watersheds to Climate Change