Caribbean Mangrove Migration (Southeast Blueprint Indicator)

Reason for Selection Mangroves are an iconic Caribbean coastal habitat that provide a wide diversity of natural and cultural resource benefits. On a global scale, mangroves in the Caribbean region make up about 12% of the worldwide population (TNC). Unfortunately, these systems have experienced significant declines globally, losing an estimated 2.1% of their area from 2000-2016 (Goldberg 2020), and as much as 20% over the last 40 years (Smith 2024). Mangroves help protect human and wildlife populations by enhancing coastal resilience. They buffer coastal communities from storm surge, which can reduce inland flooding. In addition, the aerial root systems provide natural protection in coastal environments by increasing sediment deposition, which reduces erosion rates and nutrient losses (Akram 2023). Mangroves also serve as “one of the world’s most effective natural carbon capture systems” (TNC), storing as much as five times as much organic carbon as tropical upland forests (Donato et al. 2011). Mangroves provide additional ecological benefits by serving as important habitat for resident and migratory bird communities (Acevendo 2008) as well as “hundreds of endemic species of fish” (TNC). The International Union for the Conservation of Nature (IUCN) describes mangroves as “nurseries for the world’s seafood supply”, recognizing the important they play in commercial and recreational fisheries. According to The Nature Conservancy, “with the high land-to-water ratio in the Caribbean, it is not surprising that the presence of mangroves heavily influences the health of the shorelines of multiple countries, as well as their local economies and communities. Without healthy mangroves, adjacent reefs and seagrasses are not well protected, posing challenges to species that the fishing industry heavily relies on like the Queen Conch, spiny lobster and Atlantic blue crab.” Input Data * [Southeast Blueprint 2025 extent] * 2012 [National Oceanic and Atmospheric Administration (NOAA) Coastal Change Analysis Program (C-CAP) land cover files for the U.S. Virgin Islands] (St. Thomas, St. John, and St. Croix are provided as separate rasters) accessed 4-26-2022; learn more about [C-CAP high resolution land cover and change products] * 2010 [NOAA C-CAP land cover files for Puerto Rico], accessed 4-26-2022; learn more about [C-CAP high resolution land cover and change products] * 2020 (v2.2.0) [LANDFIRE Existing Vegetation Type] (EVT), [Operational Roads] (Roads), [Slope Percent Rise] (SlpP), and [Elevation] for Puerto Rico and the U.S. Virgin Islands (U.S. Insular Areas); [access the data] Mapping Steps * Combine the C-CAP data for Puerto Rico and the U.S. Virgin Islands, reproject to Albers Equal Area, and resample to 30 m to match the resolution of the Southeast Blueprint. * Create current mangrove layer by extracting the Estuarine Forested Wetland class from C-CAP. * Create a barrier layer using LANDFIRE EVT, roads, slope, and elevation based on thresholds used by Schill et al. 2014. Include all developed classes from the EVT layer, all roads, slopes ≥10%, and elevation >2 m. Combine them all into a single barrier layer, assigning a value of 1 if any of those barriers to mangrove migration are present. * Use the ArcGIS Distance Accumulation tool to identify migration space not blocked by barriers. * Make a mask to remove areas of open water and ocean using areas of NoData (-9999) and open water (7292) in LANDFIRE EVT. * Use the resulting mask to remove open water and ocean. We use the mask after estimating migration space in order to allow mangroves to use open water and ocean to move to new sites that don’t currently have mangroves, but could in the future. This is different from the methods originally used by Schill et. al 2014. * Use the ArcGIS Region Group tool to remove isolated pixels and very small patches, retaining only areas roughly 2 acres or more in size (9 or more 30 m pixels) * Reclassify the resulting layer into the indicator categories below. * As a final step, clip to the extent of the Southeast Blueprint. Note: For more details on the mapping steps, code used to create this layer is available [in the Southeast Blueprint 2025 Data Download] or [Caribbean-only Southeast Blueprint 2025 Data Download] under > 6_Code. Final indicator values 4 = Current mangrove 3 = Potential future mangrove <0.5 km from current mangrove 2 = Potential future mangrove 0.5-1 km from current mangrove 1 = Potential future mangrove >1 km from current mangrove 0 = Not likely to be current or future mangrove Known Issues * The indicator underestimates mangrove in some areas due to classification issues with C-CAP and the age of the data missing some newly established mangroves. * The indicator overestimates mangrove extent in some areas where mangrove was cleared after 2010 (Puerto Rico) or 2012 (Virgin Islands). This is based on the age of the landcover data. Disclaimer: Comparing with Older Indicator Versions There are numerous problems with using Southeast Blueprint indicators for change analysis. Please consult Blueprint staff if you would like to do this (email [hilary_morris@fws.gov]). Literature Cited Acevedo, Miguel A.; Aide, Miguel and T. Mitchell. “Bird Community Dynamics and Habitat Associations in Karst, Mangrove and Pterocarpus Forest Fragments in an Urban Zone in Puerto Rico,” Caribbean Journal of Science 44(3), 402-416, (1 December 2008). [[https://doi.org/10.18475/cjos.v44i3.a15]]. Akram H, Hussain S, Mazumdar P, Chua KO, Butt TE, Harikrishna JA. Mangrove Health: A Review of Functions, Threats, and Challenges Associated with Mangrove Management Practices. Forests. 2023; 14(9):1698. [[https://doi.org/10.3390/f14091698]]. Bimrah, K.; Dasgupta, R.; Hashimoto, S.; Saizen, I.; Dhyani, S. Ecosystem Services of Mangroves: A Systematic Review and Synthesis of Contemporary Scientific Literature. 2022. Sustainability, 14, 12051. [[https://doi.org/10.3390/su141912051]]. Donato, D. C., Kauffman, J. B., Murdiyarso, D., Kurnianto, S., Stidham, M., and Kanninen, M. (2011). Mangroves among the most carbon-rich forests in the tropics. Nat. Geosci. 4, 293–297. doi: 10.1038/ngeo1123. [[https://www.nature.com/articles/ngeo1123]]. Goldberg L, Lagomasino D, Thomas N, Fatoyinbo T. Global declines in human-driven mangrove loss. Glob Chang Biol. 2020 Oct;26(10):5844-5855. [[https://doi.org/10.1111/gcb.15275]]. International Union for Conservation of Nature and Natural Resources (IUCN). August 24, 2017. Mangroves: nurseries for the world’s seafood supply. [[https://iucn.org/news/forests/201708/mangroves-nurseries-world%E2%80%99s-seafood-supply]]. Smith, Renée. Caribbean Biodiversity Fund. February 2, 2024. Unveiling the Marvels of Mangrove Forests: The Mighty Coastal Wetlands. [[https://caribbeanbiodiversityfund.org/blog/unveiling-the-marvels-of-mangrove-forests-the-mighty-coastal-wetlands/]]. Rull, Valentí. 2023. Rise and fall of Caribbean mangroves. Science of The Total Environment, Volume 885. Accessed November 25, 2024. [[https://www.sciencedirect.com/science/article/pii/S0048969723024725]]. The Nature Conservancy. Mangroves of the Caribbean: Vital Protectors of Reefs, Seagrass, and Coastal Economies. Accessed May 13, 2025. [[https://www.nature.org/en-us/about-us/where-we-work/caribbean/stories-in-caribbean/exploring-caribbean-mangroves/]].