Reduced pesticide toxicity and increased woody vegetation cover account for enhanced native bird densities in organic orchards.
Organic farming is often promoted as a solution for counteracting the adverse impacts of agricultural intensification on biodiversity. However, it is unclear whether the biodiversity benefits derived from organic farming require an adoption of organic farming in its entirety (i.e. a systems-level approach) or whether the benefits derived are because of just a small subset of the associated management practices. Using bird survey data collected from kiwifruit orchards in New Zealand, we assessed whether orchards managed under an organic system support higher bird densities than those under integrated management systems. To determine whether biodiversity gains might also be achieved on non-organic orchards, we tested whether variation among kiwifruit orchards in the amount of (non-crop) woody vegetation cover, density of shelterbelts and toxicity of pesticide applications are better predictors of bird densities than management systems. Composite measures of breeding season densities of all native species and the subset of native insectivores were higher on organic orchards than integrated management orchards. Densities of introduced bird species were comparable among management systems. Pesticide use and habitat composition variables were better predictors of native bird densities than management system, with native bird densities negatively associated with pesticide toxicity ranking and/or positively associated with woody vegetation cover. Synthesis and applications. A complete conversion to an organic system may not be required to improve biodiversity in agroecosystems. Instead, the transfer of specific land management practices known to benefit biodiversity in organic systems has the potential to enhance biodiversity in other more intensively managed systems (e.g. integrated management). This may be a path towards attaining biodiversity benefits at a larger scale, because such changes may be more straightforward than conversion to an organic system.