Do protected areas reduce blue carbon emissions? A quasi-experimental evaluation of mangroves in Indonesia
Daniela A. Miteva, Brian C. Murray, Subhrendu K. Pattanayak
Mangroves provide multiple ecosystem services such as blue carbon sequestration, storm protection, and unique habitat for species. Despite these services, mangroves are being lost at rapid rates around the world. Using the best available biophysical and socio-economic data, we present the first rigorous large-scale evaluation of the effectiveness of protected areas (PAs) at conserving mangroves and reducing blue carbon emissions. We focus on Indonesia as it has the largest absolute area of mangroves (about 22.6% of the world's mangroves), is one of the most diverse in terms of mangrove species and has been losing its mangroves at a very fast rate. Specifically, we apply quasi-experimental techniques (combining propensity score and covariate matching, differences-indifferences, and post-matching bias adjustments) to assess whether PAs prevented mangrove loss between 2000 and 2010. Our results show that marine protected areas reduced mangrove loss by about 14,000 ha and avoided blue carbon emissions of approximately 13 million metric tons (CO2 equivalent). However, we find no evidence that species management PAs stalled the loss of mangroves. We conclude by providing illustrative estimates of the blue carbon benefits of establishing PAs, which can be cost-effective policies for mitigating climate change and biodiversity loss.
Marine Protected Areas (MPAs): "include biosphere reserves and national parks (IUCN categories Ia, Ib, and II) and targets strict protection." (128)
Species Management Protected Areas (SPAs): "managed for specific species and habitats (IUCN category IV), and allow some types of resource extraction." (128)
Differences of protected areas (PAs) versus control villages
"compared to control villages, PA villages are poorer, less suitable for agriculture, on steeper slopes, with fewer navigable rivers, have higher population density, and have more mangroves in 2000." (132)
"PAs have a moderately statistically significant effect on reducing mangrove loss rates — on average, 10% reduction in mangrove loss from 2000 to 2006." (132)
MPAs are effective at preventing losses of mangroves, reducing mangrove loss by approximately 14,000 hectares. SPAs, on the other hand, are not effective. It is likely that this difference is due to the strict requirements of MPAs and the fact that SPAs only apply to specific species. SPAs also cannot generate revenue through tourism to the same extent that MPAs can.
"[marine PAs] reduced mangrove loss by 13% from 2000 to 2006. In contrast, [species management PAs] did not have a statistically significant effect on mangrove outcomes." (132)
There is no evidence that marine protected areas lead to increased extraction at other unprotected areas. Furthermore, marine protected areas for mangroves in Indonesia helped to avoid emissions of approximately 13 million metric tons of carbon.
"Monetizing [13 million metric tons of blue carbon] via the social cost of carbon (roughly $41/ton of CO2e base on Pendleton et al, 2012) would yield social welfare benefits of $540 million." (134)
Other impacts of PAs
"PA establishment may displace extraction to nearby unprotected areas or to the buffer zones, a phenomenon sometimes known as spillovers, slippage or leakage (Murray, 2009). However, we did not find evidence that PAs resulted in spillovers." (134)
"Vincent (2015) has posited that PA managers could be protecting key species and habitats (e.g., old growth mangroves), even though the average impacts seem small." (134)
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Murray, B. C. 2009. Leakage from avoided deforestation compensation policy: Concepts, empirical evidence and corrective policy options. In: Palmer, C., Engel, S. (Eds.), Avoided Deforestation: Prospects for Mitigating Climate Change. Routhledge, Oxford, UK.
Pendleton, L., Donato, D.C., Murray, B.C., Crooks, S., Jenkins, W.A., Sifleet, S., Craft, C., Fourqurean, J.W., Kauffman, J.B., Marba, N., Megonigal, P., Pidgeon, E., Herr, D., Gordon, D., Baldera, A. (2012). Estimating global "blue carbon" emissions from conversion and degradation of vegetated coastal ecosystems. PLoS ONE 7, e43542.
Vincent, J.R. (2015). Impact evaluation of forest conservation programs: benefit-cost analysis, without the economics. Environ. Resour. Econ. 1-14. http://link.springer.com/article.10.1007/s10640-015-9896-y#page-1 (forthcoming).