Wetland ecosystem services in California's Central Valley and implications for the Wetland Reserve Program

Abstract

Primary ecosystem services provided by freshwater wetlands in the California Central Valley, USA, include water quality improvement, biodiversity support, and flood storage capacity. We describe these services for freshwater marshes, vernal pools, and riparian wetlands and the implications for wetlands restored under USDA programs in the Central Valley. California's Central Valley is a large sedimentary basin that was once covered by grasslands, extensive riparian forests, and freshwater marshes that today have been converted to one of the most intensive agricultural areas on earth. Remaining freshwater wetlands have been heavily altered, and most are intensively managed. Nitrogen loading from agriculture to surface and groundwater in the Central Valley was estimated to be 34.7 × 106 kg N/yr. Atmospheric deposition of nitrogen in the Central Valley was estimated to be 44.3 × 106 kg N/yr, of which ∼1.5 × 106 kg N/yr was introduced directly to wetlands. Our analysis indicates that wetlands enrolled in the USDA Wetland Reserve Program (WRP) may potentially denitrify the NO3‐N load from relatively unpolluted source water in <18 days, but the potential to denitrify the NO3‐N load from highly polluted source water is uncertain. Water management strongly influences use, diversity, and abundance of avian fauna as well as other biota. Freshwater marshes in the region continue to support important populations of breeding and wintering waterfowl and shorebirds whose populations fluctuate seasonally. Avian diversity in the little remaining area of Central Valley's riparian wetlands is also high and influenced by stand maturity, heterogeneity, and diversity. USDA conservation practices that promote these characteristics may support avian diversity. Effects of USDA conservation practices on non‐avian fauna are poorly understood and warrant further study.

Demographic factors affecting population growth in giant gartersnakes

“…Because of the loss of >90% of their natural wetland habitats (Huber et al ), giant gartersnakes now largely inhabit created marshes and canals associated with rice agriculture (Halstead et al , Wylie et al ), and survival of adult giant gartersnakes has been linked to the amount of aquatic habitat surrounding an individual's home range (Halstead et al ). Most remaining wetlands used by giant gartersnakes are managed by manipulating the timing and amount of water released (Duffy and Kahara ). If the relationship between giant gartersnake survival and the timing of flooding canals were known, this function could be included in the IPM, and the elasticity of λ to this management action could be calculated.…”

Understory vegetation as an indicator for floodplain forest restoration in the Mississippi River Alluvial Valley, U.S.A.

“…Analogous patterns of understory composition were observed in the California Central Valley, U.S.A., a 5‐million‐hectare alluvial basin of two major river systems. The historic habitats were grasslands, marshes, and riparian forests along river courses, but flood regimes and land cover were vastly altered for agriculture at a scale comparable to the MAV (Duffy & Kahara ). Tree and shrub plantings are used to restore forest overstory on reclaimed riparian areas, whereas passive processes are expected to recover understory vegetation.…”

Population and Habitat Objectives for Breeding Shorebirds in California's Central Valley

“…Historically, the Central Valley contained large expanses of wetland habitat created by rainfall and snowmelt. Wetland extent was dynamic, varying from year to year with precipitation, and generally swelled with winter rains and spring snowmelt from the Sierra Nevada, gradually receding to the smallest extent in late summer or fall, before the onset of the next rainy season (TBI 1998;Duffy and Kahara 2011). Most runoff is now captured in reservoirs and other infrastructure, mitigating the extent of flooding after heavy rains, and with it some of the temporal variation in habitat availability.…”