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

Abstract

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 (WNV), 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 nondrought conditions, whereas other landowner types were more likely to continue providing irrigation during drought. Our results highlight that conservation in social-ecological systems requires assessing not only the value of historic ecological diversity, but also how novel types of socially induced diversity may benefit ecosystems.

Stability of patch‐turnover relationships under equilibrium and nonequilibrium metapopulation dynamics driven by biogeography

“…We excluded impoundments associated with rice fields because few were surveyed during the equilibrium period and they are poor rail habitats; (2) water source—natural, irrigated or both sources, which was determined from site visits and aerial imagery collected prior to the 1950s. Irrigated wetlands have more consistent and stable inundation than natural spring‐ or stream‐fed wetlands (Van Schmidt et al, 2021 ); (3) vegetative cover—wetlands with >25% ground cover of Juncus spp. (preferred by black rails) or Typha spp.…”

“…(preferred by black rails) or Typha spp. (preferred by Virginia rails), estimated during site visits; (4) land ownership (public versus private)—wetlands on private lands may be more likely to dry out, depending on landowner motivations (Van Schmidt et al, 2021 ); (5) grazing—whether sites were actively or recently grazed by cattle or goats. Heavily grazed sites have less vegetative cover and are less likely to support rails (Richmond et al, 2012 ); (6) presence of surface water—dry sites rarely support rails (Richmond, Chen, et al, 2010 ); and (7) enhanced vegetation index (EVI), which is a 30‐m resolution Landsat product that quantifies vegetation greenness whilst correcting for atmospheric conditions and canopy background noise (Huete et al, 1994 ).…”