Biodiversity Guide - The Intertwine

egional conservation strategybiodiversity guideChapter 1 Current Conditionsspecies that depend on old-growth (i.e., mature)forest or species that require native shrub communities.This likely also is the case in stateownedforests managed by the WashingtonDepartment of Natural Resources and OregonDepartment of Forestry to produce income forstate school trust programs and, to a lesser extent,in so-called matrix lands owned and managedby the federal government (especially the U.S.Bureau of Land Management and U.S. ForestService), where a focus on commercial thinningrather than clear cutting may enhance shrubcommunities and create some larger trees. Exceptionsare likely to occur along streams protectedby Oregon and Washington state forest protectionacts, where species diversity and average age maybe higher. Family-owned forests may also havegreater age and species diversity, depending onmanagement approach.In urban areas and, increasingly, in ruralareas, forests are suffering from high levels ofinvasive plant species such as English or Irish ivy(Hedera sp.), garlic mustard (Alliaria petiolata),invasive blackberry (Rubus sp.), Scotch broom(Cytisus scoparius), false brome (Brachypodiumsylvaticum), and traveler’s joy (Clematis vitalba),among others. This is especially the case alongunmanaged roadside and in riparian areas. (Formore on this issue, see Chapter 7, “Threats andChallenges.”)Old-growth/Mature ForestOld-growth and mature forest has largely disappearedwithin the greater Portland-Vancouverregion. No comprehensive layer of old-growthforest exists for the region, and conversationswith land managers suggest that only a tinyfraction of old-growth, mature, or previouslyunharvested forest remains. However, there area few small patches of old-growth forest withinthe region. Notable examples on the Oregon sideinclude two patches totaling less than 200 acreson public land on the Sandy River, a small patchalong the Clackamas River near Eagle Fern Park,and small amounts in or near Forest Park. InWashington, nearly 2,000 acres of patches thatinclude mature or old-growth forest have beenmapped; these are scattered throughout landsowned by PacifiCorp, mostly along the LewisRiver.The effort invested in mapping relatively smallareas of old-growth forest showcase the rare andvaluable nature of the region’s remaining oldgrowthforest.Table 1-2Regional Examples of Significant Prarie and Oak HabitatsThe mapping effort for this Biodiversity Guidedid not attempt to map oak and prairie habitats.Although these habitat types do fall withintree cover or other land use classes, there are nocomprehensive and accurate maps of oak andprairie habitats available for most of the regionfrom other sources. However, various Oregonentities have partial oak maps, and the WashingtonDepartment of Fish and Wildlife has mappedthousands of acres of oak and prairie habitats aspart of it Priority Habitats and Species program.The ReGAP project estimates that 3 percent(49,000 acres) of the greater Portland-Vancouverregion supports oak woodland. However, thatsmall number, which represents a 90 percent losssince 1850, is still likely to be an overestimate.This is so because, even though potentially suitablehabitat for oak woodland is widespread, fewlarge examples of oak woodlands are known toexist, and present-day oak is often mixed in withother types of trees. Data on oak savanna andprairie are similarly unreliable, although ReGAPestimates that less than 1 percent of the region(1,500 acres) is currently prairie. Reliable figuresfor the percent of oak woodland, savanna, andprairie in public ownership do not exist, but ahigh percentage is thought to be in private ownership.Table 1-2 lists some significant areas ofprairie and oak within the region.AgricultureThere are no accurate statewide or, in most cases,even county-level map layers for agriculture. Themapping effort for this Biodiversity Guide used acombination of a modeling approach and handdigitizing from aerial photographs to separateagriculture from other short-stature land covertypes. The mapping and acreage estimates inthis Biodiversity Guide lack precision aroundChristmas trees farms, nut and fruit orchards,and vineyards (all of which are likely included inother land cover categories) and probably underestimateeven row crops and grass fields becausethe hand-digitizing process excluded small areas.The hand digitizing substantially improved thequality of this land cover category.Prairie and Native OakIn 1850, prairie, oak savanna, and oak woodlandhabitats occupied about 25 percent of the greaterPortland-Vancouver region. Evidence for thiscan still be seen today in the small patches andKey Facts: “Agriculture”individual mature oak trees scattered throughoutn 22 percent of the region’s land cover —justresidential, commercial, and agricultural landsover 400,000 acres—is mapped as agriculture.and mixed within the region’s less intensivelyn 82 percent of the classified Agriculture landmanaged forestland at elevations below aboutfalls within four counties:2,000 feet. Although these habitats are scatteredn Clackamas County: 31 percent (approximatelythroughout much of the region, they are most125,000 acres)abundant in the southern end of the region,n Washington County: 23 percent (approximately93,000 acres)at the western edge of the Willamette Valley inOregon, along the Willamette River, and in then Clark County: 17 percent (approximatelyeastern edge of the region in the Columbia River68,000 acres)Gorge, especially in Washington.n Marion County: 11 percent (approximately8 45,000 acres)9Sauvie IslandWillamette NarrowsAreaCooper Mt. Nature ParkRidgefield National Wildlife Refuge ComplexWashougal Oaks PreserveLacamas Park and Lacamas PrairieLands in the Lake River/Columbia Riverlowlands between the Shillapoo Wildlife Areaand the Ridgefield National Wildlife Refuge ComplexOwner/ManagerOregon Department of Fish and WildlifeMetro, Oregon Parks and Recreationand The Nature Conservancy, among othersMetro, Tualatin Hills Parks and Recreation DistrictU.S. Fish and Wildlife ServiceWashington Department of Natural ResourcesCity of Camas, Washington Natural Heritage Programand multiple private ownersPrivate