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.

Effects of experimental nitrogen fertilization on planktonic metabolism and CO2 flux in a hypereutrophic hardwater lake.

Hardwater lakes are common in human-dominated regions of the world and often experience pollution due to agricultural and urban effluent inputs of inorganic and organic nitrogen (N). Although these lakes are landscape hotspots for CO2 exchange and food web carbon (C) cycling, the effect of N enrichment on hardwater lake food web functioning and C cycling patterns remains unclear. Specifically, it is unknown if different eutrophication scenarios (e.g., modest non point vs. extreme point sources) yield consistent effects on auto- and heterotrophic C cycling, or how biotic responses interact with the inorganic C system to shape responses of air-water CO2 exchange. To address this uncertainty, we induced large metabolic gradients in the plankton community of a hypereutrophic hardwater Canadian prairie lake by adding N as urea (the most widely applied agricultural fertilizer) at loading rates of 0, 1, 3, 8 or 18 mg N L-1 week-1 to 3240-L, in-situ mesocosms. Over three separate 21-day experiments, all treatments of N dramatically increased phytoplankton biomass and gross primary production (GPP) two- to six-fold, but the effects of N on autotrophs plateaued at ~3 mg N L-1. Conversely, heterotrophic metabolism increased linearly with N fertilization over the full treatment range. In nearly all cases, N enhanced net planktonic uptake of dissolved inorganic carbon (DIC), and increased the rate of CO2 influx, while planktonic heterotrophy and CO2 production only occurred in the highest N treatments late in each experiment, and even in these cases, enclosures continued to in-gas CO2. Chemical effects on CO2 through calcite precipitation were also observed, but similarly did not change the direction of net CO2 flux. Taken together, these results demonstrate that atmospheric exchange of CO2 in eutrophic hardwater lakes remains sensitive to increasing N loading and eutrophication, and that even modest levels of N pollution are capable of enhancing autotrophy and CO2 in-gassing in P-rich lake ecosystems.