Geography Reference
In-Depth Information
availability (Figure 12.5). All Water Availability Basins
had water at their outlets in 1990, but 8% of the WRB area
would have near zero stream flow at their outfall in 2050.
policies were based on methods and programs that existed
in 1990 but would be implemented more extensively
across the WRB. Future human growth was contained
largely within urban growth boundaries and existing
residential developments. Urban and residential devel-
opments retained more natural vegetation. By living in
higher densities, the doubled human population by 2050
required only an 18% increase in urban and rural resi-
dential land. Almost no farmland and forest was lost to
development (
12.5 Development 2050 scenario
Under the Development 2050 scenario, land use poli-
cies were relaxed and urban and rural residential land
was permitted over larger areas. Population densities in
urban growth boundaries (14.6 residents/ha) increased
by 55% relative to 1990. Urban and rural developed land
accounted for 10.4% of the total WRB area, in contrast
to 6.7% ca. 1990 and 8.3% in Plan Trend 2050. Most new
development occurred on agricultural lands in the halos
around existing towns and cities, often impacting prime
farmland. Almost a quarter of the prime farmland was lost
in the Development 2050 scenario. Though forestry prac-
tices included more clear-cutting and less stream protec-
tion than in Plan Trend 2050, major relaxation of natural
resource regulation of forest lands would be unlikely.
Terrestrial wildlife exhibited greater responses to
the practices and policies of the Development 2050
scenario than aquatic communities (Figure 12.4). Of
the 17 terrestrial wildlife species modeled for changes
in population abundance, nine experienced a 10% or
greater decline in abundance relative to 1990 and the
coyote, a habitat generalist, was projected to increase by at
least 10%. Aquatic resources modeled in the assessment
declined more than the Plan Trend 2050 projections
but only slightly more than resource conditions in 1990.
The major cause for the lack of major differences in
aquatic resource responses under the Plan Trend and
Development scenarios is the similarity of adverse effects
of agriculture and residential development in the resource
models. Stream habitats on agricultural land were not
projected to decline further with conversion to residential
use. Water consumption increased under Development
2050, though not as much as Plan Trend 2050. In a dry
summer in 2050, 230 km of 2nd to 4th order streams
and 5% of the WRB area would be dry. This surprising
difference in water use is a result of the conversion of
irrigated agricultural land to residential land.
2%), and conservation practices reduced
prime farmland and forest present in 1990 by only 15%.
Plausible future conservation actions included 30-m
riparian buffers along all streams, restoration of grass-
lands, wetlands, oak savannah, and bottomland forests,
establishment of field borders, protection of wildlife habi-
tat in environmentally sensitive areas, and a 10% increase
in irrigation efficiency. Side channels and sloughs along
the mainstem Willamette were reconnected and restored
at the same rate they have been disconnected or lost since
the 1930s. Floodplain forests along the Willamette River
were restored to meet the extent of bottomland forest
that stakeholders identified as plausible. Private forest
practices were modified to include 30-m riparian buffers
on all 2nd to 4th order streams, smaller clearcut sizes, and
green tree retention.
These modifications to agricultural and forest land uses
under the Conservation 2050 scenario increased the area
of conifer forests aged 80 years and older by 17% relative
to ca. 1990. In contrast, area of conifer forests aged 80
years and older decreased by 19% and 22% under Plan
Trend 2050 and Development 2050, respectively. The
conservation practices reversed the loss of older forests,
but the extent of these forests under Conservation 2050
would still be less than half of what occurred at the time
of EuroAmerican settlement.
Abundance and distributions of aquatic and terrestrial
wildlife increased under the Conservation 2050 scenario
(Figure 12.4). Aquatic resources responded positively to
conservation measures, particularly in lowland streams
where land conversion had altered the streams, rivers,
riparian forests, and floodplains to a far greater extent
than in the mountainous portions of the basin. Habi-
tat suitability for cutthroat trout throughout the WRB
improved as a result of riparian practices, and increased
channel complexity and extent of floodplain forest caused
fish community richness to increase in the mainstem of
the Willamette River (Van Sickle et al., 2004).
In the lowlands, changes in land use practices along
streams caused the index of biotic integrity for fish com-
munities and macroinvertebrate EPT richness to recover
<
12.6 Conservation 2050 scenario
The Conservation 2050 scenario assumed more extensive
conservation and restoration measures than are imple-
mented currently within the basin. These practices and
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