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TRACKING CHANGES IN WETLANDS WITH URBANIZATION: SIXTEEN YEARS OF EXPERIENCE IN PORTLAND, OREGON
Citation:
Kentula, M E. AND S. E. Gwin. TRACKING CHANGES IN WETLANDS WITH URBANIZATION: SIXTEEN YEARS OF EXPERIENCE IN PORTLAND, OREGON. Presented at Urban Wetlands: Sustaining Multiple Functions, Portland, OR, May 20-21, 2002.
Description:
Urban wetlands can provide valuable ecological and societal services. They also can experience rapid change with development. Data from National Wetland Inventory Maps (NWI) and a series of field studies conducted between 1987 and 1998 were used to track changes over 16 years in small ( 2 ha), palustrine emergent/open water wetlands (PEM/POW) in the rapidly developing area of Portland, Oregon. These were the wetland types most often involved in development as indicated by a survey of Section 404 permits. NWI data based on 1982 photography showed that 26% of the total resource area (linear features and polygons) was composed of wetlands 2 ha, 57% (348 ha) of which was PEM/POW. As indicated by the NWI maps, fgield data confirmed that 40% (139 ha) had been altered prior to 1982. Despite development pressure throughout the 1990s, loss of small PEM/POW wetlands due to human uses slowed between 1993-98 with only 6% of the sites being destroyed as opposed to 40% between 1982-92. Of the ten sites that were gone due to drought in 1992, seven had recovered with the return of typical rainfall; three had been destroyed. The majority of the wetlands existing in 1998 were in the regional riverine hydrogeomorphic (HGM) class (41%), while 23% were in HGM classes atypical to the region due to human manipulation. Most were in fair or marginal condition with 14% rated good and 35% poor. Land use in the vicinity of the wetlands reflected development patterns. In the early 1990s commercial and industrial uses surrounded wetlands in developed settings. By the end of the 1990s, wetlands in residential settings equaled those in commercial and industrial. These types of data document patterns in wetland loss and degradation that can be used to target management actions and improve the siting and design of restoration efforts. The next challenge is to use these and other types of data to develop strategies to manage urban wetlands in a way that maintains and ultimately improves the condition of the resource.