Habitat restoration promotes pollinator persistence in intensively-managed agriculture
Many recent studies have shown that enhancing floral resources in intensive agricultural landscapes promotes species richness of flower-visitor communities, but to date, it is not known whether such effects are transient, merely concentrating individuals from across the larger landscape at flower-rich patches. Long-term data series and use of occupancy models are particularly helpful in determining whether these richness patterns actually reflect true increases in occupancy, or not. Further, such models can also determine whether enhanced occupancy results from decreased extinction rates, increased colonization rates, or both, providing information that is useful for conservation planning. To date, these models have not been applied to the study of pollinators and their response to restoration.
Here we present the results from a long-term study chronicling how restoration and subsequent maturation of native plant hedgerows affects occupancy, persistence and colonization of bees and syrphid flies in the Central Valley of California. Using a hierarchical occupancy model, we show that restoration via the introduction of perennial flowering native shrubs promotes the between-season persistence, but not colonization, of both bees and syrphid flies. This increased occupancy has the long-term effect of leading to the assembly of more diverse communities. We also find that, for native bees, hedgerow restoration has a greater impact on floral resource specialists than generalists.