Mechanisms and impacts of an incentive-based conservation program with evidence from a randomized control trial.

Conservation science needs more high-quality impact evaluations, especially ones that explore mechanisms of success or failure. Randomized control trials (RCTs) provide particularly robust evidence of the effectiveness of interventions (although they have been criticized as reductionist and unable to provide insights into mechanisms), but there have been few such experiments investigating conservation at the landscape scale. We explored the impact of Watershared, an incentive-based conservation program in the Bolivian Andes, with one of the few RCTs of landscape-scale conservation in existence. There is strong interest in such incentive-based conservation approaches as some argue they can avoid negative social impacts sometimes associated with protected areas. We focused on social and environmental outcomes based on responses from a household survey in 129 communities randomly allocated to control or treatment (conducted both at the baseline in 2010 and repeated in 2015-2016). We controlled for incomplete program uptake by combining standard RCT analysis with matching methods and investigated mechanisms by exploring intermediate and ultimate outcomes according to the underlying theory of change. Previous analyses, focused on single biophysical outcomes, showed that over its first 5 years Watershared did not slow deforestation or improve water quality at the landscape scale. We found that Watershared influenced some outcomes measured using the survey, but the effects were complex, and some were unexpected. We thus demonstrated how RCTs can provide insights into the pathways of impact, as well as whether an intervention has impact. This paper, one of the first registered reports in conservation science, demonstrates how preregistration can help make complex research designs more transparent, avoid cherry picking, and reduce publication bias.

Mecanismos e Impactos de un Programa de Conservación Basada en Incentivos con Evidencias de un Ensayo Aleatorio de Control Resumen Las ciencias de la conservación necesitan evaluaciones de impacto de mayor calidad, especialmente aquellas que exploran los mecanismos del éxito o del fracaso. Los ensayos aleatorios de control (RCTs) proporcionan evidencias particularmente sólidas de la efectividad de las intervenciones (aunque han recibido críticas por considerarlas reduccionistas e incapaces de proporcionar conocimiento sobre los mecanismos) pero ha habido pocos experimentos de ese tipo que investiguen los efectos de la conservación a escala del paisaje. Exploramos el impacto de Watershared, un programa de conservación basada en incentivos en marcha en los Andes bolivianos, con uno de los pocos RCTs existentes de conservación a escala de paisaje. Existe un gran interés por dichas estrategias de conservación basada en incentivos pues hay quienes argumentan que pueden evitar los impactos sociales negativos que a veces se asocian con las áreas protegidas. Nos enfocamos en los resultados sociales y ambientales con base en las respuestas de una encuesta a hogares en 129 comunidades asignadas al azar para controlar o tratar (ambas encuestas realizadas en la línea base en 2010 y repetidas en 2015/16). Impusimos un control para la aceptación incompleta del programa al combinar el análisis estandarizado de RCTs con métodos de emparejamiento e investigamos los mecanismos mediante la exploración de resultados intermedios y finales de acuerdo con la teoría subyacente del cambio. Los análisis previos, enfocados en resultados biofísicos únicos, mostraron que durante los primeros cinco años del programa Watershared, la deforestación no experimentó una desaceleración y tampoco hubo mejoras en la calidad del agua a escala de paisaje. Descubrimos que Watershared influyó sobre algunos resultados medidos con la encuesta, pero sus efectos fueron complejos y algunos fueron inesperados. De este modo demostramos como los RCTs pueden proporcionar conocimiento sobre las vías de impacto, así como también si una intervención genera un impacto. Este artículo, uno de los primeros reportes registrados en las ciencias de la conservación, demuestra cómo el prerregistro puede ayudar a hacer más transparentes los diseños complejos de investigación, evitar la selección subjetiva de datos y reducir el sesgo de publicación.

The effectiveness of Payments for Ecosystem Services at delivering improvements in water quality: lessons for experiments at the landscape scale.

BACKGROUND: Randomised Control Trials (RCTs) are used in impact evaluation in a range of fields. However, despite calls for their greater use in environmental management, their use to evaluate landscape scale interventions remains rare. Payments for Ecosystem Services (PES) incentivise land users to manage land to provide environmental benefits. We present the first RCT evaluation of a PES program aiming to improve water quality. Watershared is a program which incentivises landowners to avoid deforestation and exclude cattle from riparian forests. Using this unusual landscape-scale experiment we explore the efficacy of Watershared at improving water quality, and draw lessons for future RCT evaluations of landscape-scale environmental management interventions. METHODS: One hundred and twenty-nine communities in the Bolivian Andes were randomly allocated to treatment (offered Watershared agreements) or control (not offered agreements) following baseline data collection (including Escherichia coli contamination in most communities) in 2010. We collected end-line data in 2015. Using our end-line data, we explored the extent to which variables associated with the intervention (e.g. cattle exclusion, absence of faeces) predict water quality locally. We then investigated the efficacy of the intervention at improving water quality at the landscape scale using the RCT. This analysis was done in two ways; for the subset of communities for which we have both baseline and end-line data from identical locations we used difference-in-differences (matching on baseline water quality), for all sites we compared control and treatment at end-line controlling for selected predictors of water quality. RESULTS: The presence of cattle faeces in water adversely affected water quality suggesting excluding cattle has a positive impact on water quality locally. However, both the matched difference-in-differences analysis and the comparison between treatment and control communities at end-line suggested Watershared was not effective at reducing E. coli contamination at the landscape scale. Uptake of Watershared agreements was very low and the most important land from a water quality perspective (land around water intakes) was seldom enrolled. DISCUSSION: Although excluding cattle may have a positive local impact on water quality, higher uptake and better targeting would be required to achieve a significant impact on the quality of water consumed in the communities. Although RCTs potentially have an important role to play in building the evidence base for approaches such as PES, they are far from straightforward to implement. In this case, the randomised trial was not central to concluding that Watershared had not produced a landscape scale impact. We suggest that this RCT provides valuable lessons for future use of randomised experiments to evaluate landscape-scale environmental management interventions.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project.

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

A global model of the response of tropical and sub-tropical forest biodiversity to anthropogenic pressures.

Habitat loss and degradation, driven largely by agricultural expansion and intensification, present the greatest immediate threat to biodiversity. Tropical forests harbour among the highest levels of terrestrial species diversity and are likely to experience rapid land-use change in the coming decades. Synthetic analyses of observed responses of species are useful for quantifying how land use affects biodiversity and for predicting outcomes under land-use scenarios. Previous applications of this approach have typically focused on individual taxonomic groups, analysing the average response of the whole community to changes in land use. Here, we incorporate quantitative remotely sensed data about habitats in, to our knowledge, the first worldwide synthetic analysis of how individual species in four major taxonomic groups--invertebrates, 'herptiles' (reptiles and amphibians), mammals and birds--respond to multiple human pressures in tropical and sub-tropical forests. We show significant independent impacts of land use, human vegetation offtake, forest cover and human population density on both occurrence and abundance of species, highlighting the value of analysing multiple explanatory variables simultaneously. Responses differ among the four groups considered, and--within birds and mammals--between habitat specialists and habitat generalists and between narrow-ranged and wide-ranged species.