Biogeography of the Greater Portland-Vancouver ... - The Intertwine

egional conservation strategybiodiversity guideChapter 2 Biogeography of the Greater Portland-Vancouver RegionTable 2-1Subbasins Used for Analysis of Vegetation ChangeNumber Basin Acres1 Abernethy Creek-Willamette River 87,1052 Cathlamet Channel-Columbia River 21,9443 Chehalem Creek-Willamette River 78,1574 Clackamas River 158,2385 Johnson Creek 60,1106 Lewis River 220,7367 Molalla River 180,8668 Salmon Creek-Frontal Columbia River 137,3419 Sandy River 67,12310 Scappoose Creek-Frontal Columbia River 125,28711 Tualatin River 452,98112 Washougal (City)-Columbia River 47,69613 Washougal River 102,12814 Willamette River-Frontal Columbia River 89,032Total 1,828,745runs roughly east through the southern portionof the region and then turns north after passingWilsonville, before joining the Columbia northof Portland. The foothills of the Cascade Rangedefine the eastern portion of the region, whilethe Coast Range foothills define the northwest.The Tualatin Mountains form a forested spinethrough the city of Portland, running southeastnorthwestfrom Lake Oswego to the Coast Rangeabove Scappoose. The Chehalem Mountainsextend west and then northwest from Sherwoodto Forest Grove. A series of geologically recentvolcanic cones collectively named the East Buttesdot southeast Portland and the lower Clackamaswatershed.Near the end of the last ice age (approximately12,000 years ago), the Missoula Floods carvedout the Columbia River Gorge, flooded what isnow the Portland-Vancouver area, altered rivercourses, and deposited rocks and rich sedimentsonto the valley floor.The greater metropolitan areas of Vancouver,Washington, and Portland, Oregon, are hometo the lion’s share of the region’s residents: 2.1million, as of 2010, with approximately 1 millionmore residents expected over the next 25 years.Although urban areas extend throughout theregion, development is densest near its center,roughly at the confluence of the Willametteand Columbia rivers. The population generallybecomes sparser toward the perimeter. Oregoncities include Beaverton, Canby, Estacada, ForestGrove, Gresham, Hillsboro, Lake Oswego,Milwaukie, Newberg, Portland, Scappoose, St.Helens, Sherwood, Troutdale, Wilsonville, andWoodburn. Washington cities include BattleGround, Camas, La Center, Ridgefield, Vancouver,Washougal, and Woodland.As in much of the Willamette Valley, butin contrast to much of the rest of Oregon andWashington, the region’s land base has littlefederal land ownership. However, 239,352 acres(13.1 percent of the region) are in public ownership,with significant areas owned by Metro,the states of Oregon and Washington, and localjurisdictions (see Figure A-5). Federal ownershipis restricted mostly to three wildlife refuges andsome areas on the fringe of the region, such as thewestern end of the Columbia River Gorge ScenicArea. Some important natural areas are listedin Table 2-2. In addition, the states of Oregonand Washington manage substantial forestedareas—in the Coast Range foothills and Cascadefoothills, respectively—for income for schooltrusts and other public benefits.The south/southwest portion of the region ispart of the Willamette Valley proper. Like most ofthe valley, this former prairie and savanna area isdominated by agriculture, with significant acreagein grass seed. The lower, flatter, undevelopedareas of the Tualatin Basin also are predominantlyagricultural, as are the Columbia River lowlands(excluding Vancouver and other urban areas) andmuch of Sauvie Island. Vineyards have extendedthe reach of agriculture to steeper slopes inwarmer microclimates, especially in the rainshadow of the Coast Range at the western edge ofthe Willamette Valley. Nurseries occupy significantareas in the mid-elevation portions of ruralMultnomah, Clackamas, and Clark counties andelsewhere. Forests and forestry dominate undevelopedlandscapes elsewhere, particularly abovethe 1,000-foot level.With this unique geographic and culturalsetting, the region understandably hasunique and diverse flora and fauna, andcorrespondingly unique conservation challengesand opportunities.Habitat Change in the Region,1850-2010John A. Christy, Oregon Biodiversity InformationCenter, Portland State University 1Analysis of changing land cover in the greaterPortland-Vancouver region since 1850 indicateswhich habitats have sustained the greatestimpacts from settlement, and by proxy, whichTable 2-2Important Natural Areas in the Greater Portland-Vancouver Region409 species of native wildlife, including at least 47fish species, 18 amphibians, 14 reptiles, 219 birds,AreaOwner/Manager66 mammals, and 59 types of butterflies. TheseTualatin, Ridgefield, Steigerwald Lake, Franz Lake, U.S. Fish and Wildlife Servicenumbers exclude thousands of other invertebrateand Pierce Lake National Wildlife Refugesspecies (see Appendices E, G and H).The region is blessed with several major rivers—theClackamas, Columbia, Lewis, Molalla,Sauvie Island, Multnomah Channel, and Palensky State Oregon Department of Fish and Wildlife,Wildlife Areas (Palensky Wildlife Area isMetro, and Bonneville Power AdministrationSalmon, Sandy, Tualatin, Washougal, and Willamette—andwithin Burlington Bottoms)many smaller rivers, creeks, andsloughs. Lakes are few and mostly have beenForest ParkCity of Portlandaltered for water supply and flood control; theyinclude Sturgeon, Smith, Bybee, Vancouver,Molalla River State Park, the Lower Sandy River Gorge, Multiple ownersLacamas and Hagg lakes; Lake Oswego; andthe Lower Clackamas RiverKellogg, Merwin and Scroggins reservoirs. Thesewater bodies support at least two dozen nativeWillamette NarrowsMetro and Oregon Parks andfish species, including iconic runs of salmon andRecreation Departmentsteelhead.Shillapoo Wildlife AreaWashington Department of Fish andThe Willamette and Columbia rivers divideWildlifethe region roughly into thirds (see Figure A-1).The Columbia runs west, dividing Oregon andWashington before heading north as it passes1 This section is abstracted from the report Changing Habitats in the Portland-Vancouver Metro Area, 1850-2010, produced by Johnthrough Portland and Vancouver. The WillametteA. Christy of the Oregon Biodiversity Information Center for the Regional Conservation Strategy and Biodiversity Guide project.Details on analytic methods are found in the full report, which is available on request from Metro’s Natural Areas Program).16 171

egional conservation strategybiodiversity guideChapter 2 Biogeography of the Greater Portland-Vancouver RegionPre-settlement mappingefforts did not map orgrossly under-representedhabitats that existedas smaller patches(non-matrix types).As a result, data foremergent wetalnd,riparian forest, shrubswamp and shrublandlikely grossly under-estimate the degree ofloss since 1850.Table 2-3Acreage, Percent of Total Area, and Percent Change for 11 Land Cover Types in the Regionspecies assemblages are most at risk. In orderto provide information at both the regional andsubwatershed scales, data were analyzed for theregion as a whole and for 14 separate subbasins(HUC 4 and HUC 5 and Table 2-1). The mainsources of data were General Land Office landsurvey data from the 1850s, U.S. Forest Servicemaps of forest type from the 1930s, and— for2010 vegetation—ecological system life form datacreated for the U.S. Geological Survey’s gap analysisprogram. Eleven land cover types(Table 2-3) were used to analyze changes inhabitat. (For methods, see “Data Sources andMethods,” below.)Results indicate that agriculture and urbandevelopment have caused the greatest changesin land cover in the region, and oak, prairie,and savanna habitats have sustained the greatestlosses. Changes at the subbasin level vary widely,depending mostly on the location of subbasinrelative to urban development and farmland.Extensive areas of commercial forest at the edgesof the region keep overall forest cover high;1850 2010Land Cover Type Acreage % of Total Acreage % of Total % ChangeAgriculture 0 0.00 500,174 27.35 n/aEmergent wetland 7,164 0.39 21,457 1.17 199.50Mixed forest 1,205,245 65.90 778,118 42.55 -35.44Oak 198,995 10.88 49,244 2.69 -75.25Prairie and savanna 266,296 14.56 1,494 0.08 -99.44Riparian and wet forest 80,016 4.38 83,046 4.54 3.79Shrub swamp 7,721 0.42 6,562 0.36 -15.02Shrubland 428 0.02 3,265 0.18 662.94Unvegetated 669 0.04 1,573 0.09 135.14Urban 0 0.00 328,838 17.98 n/aWater 62,205 3.40 54,976 3.01 -11.62TOTAL 1,828,740 100 1,828,745 100although more urbanized subbasins have lostsubstantial forest cover.Limitations of the DataSource data are generally accurate for large-scalefeatures but commonly misclassify or underestimatethose types occurring in small areas. Consequently,less emphasis should be placed on figuresfor small-patch cover types, including emergentwetland, riparian forest, shrub swamp, shrubland,and unvegetated land. The use of small-patchcover types here is limited to analysis of whathistorical types were converted to agriculture andurban cover.Vegetation Change over the RegionHistorically, about 50 percent of the region wascovered by conifer/mixed forest and 16 percentwas burned forest, with most of the remainingarea covered in prairie or savanna (14.6 percent),and oak (10.9 percent). By 2010, nearly half of theregion had been converted to either agriculture(27.4 percent) or urban and suburban development(18 percent). Prairie, savanna, and burnedforest had essentially disappeared, and oak wasreduced to 2.7 percent. Combined non-oak forestcover declined about 35 percent. Changes in thesix small-patch cover types (Table 2-3) in thestudy area are difficult to explain and to a largedegree represent differences in classification inthe underlying data sets.More detailed vegetation change by subbasinis presented in each subbasin description (seeAppendix I).Vegetation Change by SubbasinThe 14 subbasins vary greatly in size, historicaland current species composition, and relativeamounts of agricultural and urban development(see Table 2-3). Changes in the subbasins largelyreflect differences in the history of settlementand development. Basin-by-basin changes in thefour cover types of greatest conservation concernare shown in Figure 2-2. Prairie/savanna andoak showed consistent losses across all subbasinsexcept the Sandy River (this exception probablyis attributable to misclassification in the data set),averaging 85 percent and 63 percent, respectively.Mixed forest declined an average of 35percent in all subbasins except for the Chehalem,where it showed an 81 percent gain, presumablybecause—in the absence of fire—Douglasfir and other upland forest trees invaded prairie/savanna and oak habitats. Water showed declinesin the Cathlamet, Salmon, Scappoose, and Willamettesubbasins but increases in the Clackamasand Molalla subbasins. Losses in the formerpresumably are due to drainage and diking foragriculture, while the gains in the Clackamasand Molalla subbasins may be attributable to thecreation of gravel pits. The large increase in waterin the Lewis River subbasin is attributable to theconstruction of flood control reservoirs after1931. Agriculture and urban forest were excludedfrom Figure 2-1 because they were not presentin 1850.Historically, the following basins consisted ofmore than 20 percent prairie or savanna habitat:Molalla River (37 percent), Chehalem Creek(29 percent), Clackamas River (27 percent), AbernethyCreek (26 percent), and Cathlamet Channel(25 percent). With the exception of the CathlametChannel subbasin, prairies in Washington weresmall and scattered but relatively numerous. Veryfew are left today in the region, and prairies are ofgreat conservation concern. Oak habitat coveredmore than 20 percent of two subbasins—Chehalem Creek (60 percent) and Tualatin River(20 percent)—but never was extensive in theWashington portion of the region.Today, urbanized land represents more than20 percent of the following subbasins: JohnsonCreek (69 percent), Willamette (62 percent),Salmon Creek (32 percent), Abernethy Creek(26 percent), and Tualatin River (21 percent). Innine basins, agriculture represents more than 20percent of the land; these basins are ChehalemCreek (67 percent), Molalla River (51 percent),FIGURE 2-3Relative Percent Change of Major Land Covers, 1850-2010,forfigurethe Region2-1Excludes Relative Emergent Percent Wetland Change and of Shrubland Major Land Because Covers, of Differences 1850-2010, in Data Setsfor the RegionExcludes Emergent Wetland and Shrubland Because of Differences in Data Sets18 191000-100AgricultureMixed forestOakPrarie andSavannahRiparian andWet ForestShrub swampUnvegetatedUrbanWater

egional conservation strategybiodiversity guideChapter 2 Biogeography of the Greater Portland-Vancouver Regiontable 2-4Regional Biodiversity Assessments Conducted since 1990Plan or Project Geography and Project Leader and CommentsPurposeKey ParticipantsPlan or Project Geography and Purpose Project Leader and CommentsPurposeKey ParticipantsClark County Legacy Lands Greater VancouverClark County and a coalition of public Expert opinion-based effort; for informationWashington Conservation Washington stateOregon Department of Fish and No specific conservation opportunity areasabout projects and data contact pat-Strategy, 2006Washington Department of Fish and are identified. Scale is too large to provideProject, 1992 and onward metropolitan regionagencies, nonprofit conservationIdentified priority species andorganizations, private landowners, rick.lee@clark.wa.gov or see http://www.Wildlife and many stakeholders the level of detail needed in the greaterIdentify and implementhabitats; conservation opportunityareas as in Oregon’sand the communityco.clark.wa.us/legacylands/index.htmlPortland-Vancouver region.actions to protect, conserve,and restore the system ofstrategy were not mappednatural areas, trails, andopen spacesNature Conservancy Pacific Oregon and Washington The Nature Conservancy withThe Biodiversity Guide links to theseNorthwest Coast Ecoregional Coast Rangestakeholders and expert review by assessments, for the most part notOregon Biodiversity Project, Oregon statewideDefenders of Wildlife and many Identified about 18% of the state. TheAssessment, 2006Identified focal area formany agencies and organizations overlapping with them.1993-1999stakeholdersvalue of urban areas largely is overlookedHigh-priority conservationbiodiversity conservationat that scale.areas in OregonNatural Features Project, Addressed much of the Coalition of government agency and Expert opinion-based effort, polygonsWillamette Basin Alternative Willamette BasinPacific Northwest EcosystemDoes not include Washington portions of2006greater Portland-Vancouver nonprofit organizations under the are not delineated, and there are noFutures: Conservation andResearch Consortium, led by the the greater Portland-Vancouver regionregion (excluding Washington) auspices of Metro Greenspaces Policy attributes.Presented an achievableRestoration Option, 2002University of Oregon and OregonAdvisory Committeevision of conservation andState University, with many partnersrestoration opportunity areasand many stakeholders providingNature Conservancy East Oregon, Washington, and The Nature Conservancy with stakeholdersand expert review by many assessments, for the most part notThe Biodiversity Guide links to thesethat would still allow forfeedbackand West Cascade Mts. EcoregionalAssessment, 2007agencies and organizationsoverlapping with them.Northern Californiaanticipated growthIdentified focal areas forMetro Title 13 Regionally Extends to one mile outside Metro staff, jurisdictions, Department Focused on a smaller watershed-specificbiodiversity conservationSignificant Fish and Wildlife the urban growth boundary of Land Conservation and Development,scale. Oregon portion of the region only.and stakeholder steeringWillamette Synthesis Project, Willamette BasinThe Nature Conservancy with stake-Provides a good starting point; however,Habitat Inventory, 2005Used to provide scientificcommittee2009holders and review by many agencies as with the state conservation strategies,context for meeting Oregon’sIntegrated previous assessmentsand updated state ofand organizationsthe scale is too large to provide the levelland use Goal 5 requirementsof detail needed in our region.Oregon conservation opportunityActions for Watershed Health: City of PortlandCity of Portland Bureau ofCity of Portland boundary.areas with better dataPortland Watershed ManagementPlan, 2005Oregon and Washington Lower Columbia watersheds ODFW in Oregon and Lower Columbia Information from this plan is used in theEnvironmental ServicesGuides City decisions andprojects by providing aRecovery Plans for Lower of Oregon and Washington Fish Recovery Board in Washington, Biodiversity Guide.comprehensive approach toColumbia River Salmon andwith participation by many stakeholdersrestoring watershed health.Set programmatic and geographicpriorities for salmonSteelhead, 2010Framework for Integrated City of PortlandCity of Portland Bureau ofCity of Portland boundary. Includes annualand steelhead recoveryManagement of WatershedEnvironmental ServicesreportsScience to guide City decisionsthat affect watershedHealth, 2006U.S. Fish and Wildlife Service, Willamette Valley and Institute for Applied Ecology for U.S. Information from the recovery plan isRecovery Plan for the Prairie southern Puget Trough Fish and Wildlife Service; many partnersprovided inputused in the Biodiversity Guide.health; ensures cross-bureauSpecies of Western Oregonconsistency; establishesIdentified actions and goalsand Southwestern Washington,2010goals, objectives, indicatorsfor prairie and savannaof success.conservation to benefit listedspeciesOregon ConservationOregon statewideOregon Department of Fish and Limited information on urban areas. TheStrategy, 2006Identified priority species andWildlife and many stakeholders scale is very coarse.Watershed-based AssessmentsPlans and assessments Developed by watershed councils and Factored into the Biodiversity Guide.habitats and conservationThe strategy will be updated in the nextand Plans (various). typically tied to watershed or similar groups or agenciesopportunity areasfew years. Conservation opportunity areassubwatershed boundariesin the greater Portland-Vancouver areawill be based on work of the WillametteSynthesis project.22 23