Assessing impacts of social-ecological diversity on resilience in a wetland coupled human and natural system: Data release

[Methods] We mapped all emergent wetlands > 5×5 m within our study area—California’s Sierra Nevada foothills EPA zone III eco-region in Yuba, Nevada, and southern Butte countieso of California. Mapping was done by manually interpreting summer 2013 GeoEye-1 0.4 m imagery in Google Earth 7.1.5. Areas covered by hydrophytes (Typha spp., Scirpus spp., Juncus effusus, Leersia oryzoides, or various sedges) were considered wetland. We included hydrophytes that appeared seasonally dried; if green vegetation was present along the wetland-upland transition zone, we buffered 5 m into it. Open water and rice were excluded. If imagery was ambiguous, we used Google Earth imagery from adjacent years to help distinguish if a wetland was present. Each wetland’s geomorphology was classified as slope (shallow hillside flow), pond fringe, fluvial, rice fringe, irrigation ditch, or waterfowl impoundment. We combined historic imagery and field data to determine the water sources. We surveyed 237 wetlands for occupancy of Black Rails up to three times each summer from 2012–2016 using established broadcast survey methods (for details see Richmond et al. 2010). To assess the effects of water source on wetland hydrology, we resurveyed wetlands for 14 periods: in the early wet season (January 8–27), late wet season (March 22–25), early dry season (May 17–June 20), and late dry season (July 15–August 15) from summer 2013–2016. At each visit we walked throughout the wetland with a map of aerial imagery and recorded the percent wetness (areal percent of wetland saturated with water). We trapped mosquitoes at 63 wetlands from June–October, 2012–2014 (4710 trap/nights) and estimated WNV prevalence (probability of a mosquito testing positive for WNV) with genetic testing. We estimated WNV transmission risk at each wetland as the mean abundance of WNV-infected Culex spp. (the main WNV vectors) per trap/night. [Usage Notes] Note that wetland data is not a comprehensive list of all wetlands in the region. Missing values for black rail occupancy in some years or visits within years are delineated with Theory posits that resilience of ecosystems increases when there is a diversity of agents (e.g., species) and linkages between them. If ecosystems are conceptualized as components of “coupled human and natural systems”, then a corollary would be that novel types of human-induced diversity may also foster resilience. We explored this hypothesis by studying how socially created diversity mediated the impact of a historically severe drought on a network of wetlands in the foothills of the California Sierra Nevada containing a metapopulation of the threatened California Black Rail (Laterallus jamaicensis coturniculus). We examined how (1) diversity in motivations for land ownership affected use of irrigation water and response to drought, (2) differences in natural and irrigated water sources affected wetland drying in response to drought, and (3) these processes affected the persistence of rails and the transmission risk of West Nile virus, an emerging infectious disease that threatens people and rails. Wetlands were mostly fed by inefficiencies and leaks from the irrigation system. Wetlands with both natural and irrigated water sources were larger, wetter, and likelier to persist through drought because these two sources showed response diversity by drying at different times. Wetlands with diverse water sources also provided the best habitat for the California Black Rail, and irrigation appeared responsible for its persistence through the drought. Irrigation increased WNV transmission risk by increasing the quantity, but not the quality, of wetland habitats for mosquitoes. The impacts of social diversity were more ambiguous, with redundancy prevalent. However, profit-motivated landowners provided wetlands more irrigation during non-drought conditions, while other landowner types were more likely to continue providing irrigation during drought. This dataset provides the wetland, California Black Rail, and West Nile virus data that support the findings of this study. Partial social and geospatial data are available by emailing the first author upon request, excluding some information that would make respondents identifiable.