Abstracts

Presented by Cliff Feldheim - Email: Cliff.Feldheim@water.ca.gov

Habitat loss poses the greatest threat to species across the world and is the most significant contributor to reductions in biodiversity and animal populations. Wetlands, among the most biodiverse and economically valuable ecosystems, have suffered some of the greatest losses due to urbanization and changes in agriculture and land use. In Californias Central Valley (Valley), substantial wetland losses coincide with significant population declines of locally breeding waterfowl. With this study we evaluated habitat loss through land-use changes across time (1998-2016) throughout the Valley, and its impact to breeding duck populations. With satellite imagery from 1998 and 2016, we classified habitat across 63 aerial transects from the Sacramento, Delta-Yolo, San Joaquin, and Tulare Basins within the Central Valley Joint Venture, into optimal (wetlands/rice), suboptimal (pasture/crops) and unusable (orchards/urban) waterfowl habitat. We estimated changes in breeding duck populations by averaging counts from the same transects, over two 5-year periods spanning the habitat assessments (1996-2000 and 2014-18). Duck populations exhibited large reductions across approximately 90% of the area, and despite land management plans focused on wetland restoration to benefit duck populations, only 1.8% of unusable habitat has been converted back to wetlands. Between 1998 and 2016, 13% of previously usable habitat (optimal/suboptimal) has been converted into non-usable orchards or urban areas. Our results suggest that appropriate management strategies could help slow population declines of locally nesting ducks if focused on the impacts of urbanization or agricultural land use conversion from rice to orchards.