Conserving Freshwater and Coastal Resources in a Changing Climate

Table 2. Freshwater Wetlands: Impacts of Climate Changes
Climate Driven Change
Anticipated Effects on
Freshwater Wetland
Potential Response of
Wetland
• Lower summer water
levels
• More frequent
droughts
• Increase of isolation and
fragmentation within wetlands
• Drying of bogs
• Loss of habitat, migration corridors;
Organisms dependent on water for
mobility may be threatened
• Amphibian and fish reproduction fail
more often in drier years
• Loss of hydrologic connections to
riparian zones and groundwater systems
Decrease in precipitation
falling as snow, resulting in a
meager snow pack
Annual spring flood may occur earlier
and be weaker than current patterns
Vegetation shift as the less flood-tolerant
species out-compete those which need
predictable inundation
Warmer Temperatures
• Increase in evaporation
• Decrease in dissolved oxygen in
the water
• Exacerbates the already low
summer water levels
• Survival of species compromised
due to lack of oxygen
• Species at southern extent of their
range may become extinct
Increased winter storm
intensity
• Wetlands more vulnerable to
intense wind and rain activity
• Increase in storm-water run-off
carrying pollutants, sediment and
excess nutrients
• Wetlands may be compromised
or destroyed
• Increased pollution levels in
surrounding water sources as wetlands
ability to filter is compromised
Loss of Wetland Filtering Capacity
The combination of more frequent droughts and heavy
storms is likely to reduce the capacity of wetlands to
filter sediment and pollutants. Less filtering will yield
increased levels of sediments and toxins in the surrounding
waters. Additional pollution could enter the
ecosystem as water levels drop in rivers and lakes and a
greater amount of soil is exposed to the air. Increases in
oxygen concentration within the soil, especially when
coupled with acid deposition, may trigger the release of
metals such as cadmium, copper, lead and zinc into the
environment. These additional loadings could amplify
problems in areas where there are already an elevated
prevalence of heavy metal contamination such as near
industrial discharges (Kling et al., 2003).
The level of overall nutrients being delivered into
the wetlands may decrease in summer as the freshwater
Conserving Freshwater and Coastal Resources in a Changing Climate
sources, which typically provide the majority of nutrients,
are compromised by drought conditions (Kling et
al., 2003). Despite an increase in decomposition rates
from increasing temperatures, the warmer air and water
combined with fluctuating water levels are likely to
reduce the wetland’s capacity to assimilate nutrients
and other materials transported in stormwater runoff
(Kling et al., 2003).
Altered Flooding of Floodplain Forests
A key source of water for floodplain forests and wetlands
is the flood regime of the river, stream or lake along
which they exist (Sorenson et al., 1998). Water levels
fluctuate in time with the flooding, evaporation and soil
saturation (Moore et al., 1997; Department of Ecology,
2007). Floodplains also receive water directly from
rain, groundwater and surface run-off but are adapted
to the cycles of inundation and disturbance associated
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