Remnant woodland biodiversity gains under 10 years of revealed-price incentive payments.
Evaluation of conservation incentive programme outcomes is needed to direct future investment, however, monitoring of large-scale programmes is relatively rare. Research in this area has frequently relied on space-for-time substitution or similar designs, rarely controlling for counterfactual trends or potential learning or leakage effects using repeated measures taken before and after intervention at impact and independent control sites. Using a Before-After-Control-Impact (BACI) monitoring design, we investigate the ecological impact of a conservation stewardship programme, where landholders set their own contract price through a reverse auction. In order to maintain or increase species and structural diversity of remnant native vegetation, contracted landholders agreed to manage grazing pressure (from stock and feral animals), control weeds and retain fallen logs. We test whether impact sites (private land under contract) changed over a 9-10 year period relative to control sites (independently managed, non-contracted private land) and reference sites (public conservation areas). Modest improvements were detected in native plant species richness, log abundance and grazing pressure at impact sites compared with background changes observed at control sites. While log abundance and grazing pressure were directly managed at impact sites, the improvement in native plant species richness was assumed to be influenced by reduction in multiple pressures such as grazing pressure and weed abundance. No significant intervention effects were detected in other variables including regeneration, plant litter cover, weed cover and canopy dieback. However, these variables did show changes over time which were likely due to weather, particularly an extended period of drought followed by unusually high rainfall. Policy implications. This study shows that revealed-price incentive contracts can produce biodiversity improvement compared with the business-as-usual scenario of native vegetation management on private land. The use of a Before-After-Control-Impact monitoring design enabled the separation of treatment effects from background changes such as those linked to climate and weather, demonstrating the importance of this approach for programme evaluation. We recommend the allocation of appropriate resources for monitoring and also highlight the need for the collection of baseline data prior to contract establishment at both impact and independently managed control sites.