This respository contains code and data needed to reproduce “Assessing the Population-level Conservation Effects of Marine Protected Areas” by Ovando et al. 2021. The manuscript in Conservation Biology can be accessed at https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.13782
Marine Protected Areas (MPAs) cover 3-7% of the world’s ocean, and international organizations call for 30% by 2030. While numerous studies show that MPAs produce conservation benefits inside their borders, many MPAs are also justified on the grounds that they confer conservation benefits to the broader population beyond their borders. We examine the conditions under which MPAs can provide population-level conservation benefits inside and outside their borders, and show that even in cases where the population benefits are large, they are inherently difficult to detect empirically. A network of MPAs was put in place in The Channel Islands National Marine Sanctuary in 2003, with a goal of providing regional conservation and fishery benefits. Evidence indicates that the Channel Island MPAs have increased biomass densities inside the MPAs, but we are unable to find a clear effect of these same MPAs at the population level using a Bayesian difference-in-difference approach. We show that MPA effect sizes less than 30% are likely to be difficult to detect (even when they are present); smaller effect sizes (which we find are common) are even harder to detect. Our results provide a novel assessment of the population-level effects of a large and iconic Marine Protected Area
The script make-pop-effects-of-mpas.R will reproduce all results and
manuscripts for this project.
This project is set up with
renv to manage
package dependencies. Inside R (and with your working directory set
correctly) run renv::restore(). Follow all prompts. This will install
the correct versions of all the packages needed to replicate our
results. Packages are installed in a stand-alone project library for
this paper, and will not affect your installed R packages anywhere else.