The Belize Barrier Reef (BBR) is the largest barrier reef system in the Western Hemisphere, and it has been recognized worldwide for its biodiversity since it was named a World Heritage Site by UNESCO in 1996. The South Water Caye Marine Reserve (SWCMR), a Marine Protected Area (MPA) around a southern portion of the BBR, is populated by small mangrove islands, patch reefs, and seagrass beds. These sensitive marine and terrestrial ecosystems serve as habitat for many threatened species and important commercial, recreational, and subsistence fisheries.   Despite its protected status, the complex environments in the SWCMR have not yet been mapped in detail due to limits in remote sensing technology. This study fills this knowledge gap by using high resolution CubeSat imagery and Land Use Land Change (LULC) metrics to quantify ecological and anthropogenic changes in land and water cover in the SWCMR between 2010 and 2019. A simultaneous content analysis of the reserve’s past management plans and reports isolates change drivers that may be affecting the reserve area. Together, these two halves of this mixed-methods study provide a complete picture of change inside and outside the marine reserve area between 2010 and 2019.   Results show long term changes in the seagrass, barren areas, and impervious surface cover types that may be the result of three specific change drivers. While each type of land and water cover fluctuated some over the past decade, similar stable trends were measured in and outside the SWCMR. The overall amount of seagrass cover decreased by 0.74%, and the amount of barren and developed areas in the reserve increased by 0.16%. The developed areas also experienced significantly high rates of change: 15% per year. Regardless of year, author, or type of document, all content reviewed in the content analysis points to policy and institutional factors, biophysical drivers, and infrastructure extension as the most common sources of instability in the SWCMR. They also emphasize climate change as the greatest change of concern to area stakeholders. While some of the change measured may be unstable or negligible, these findings reveal that anthropogenic landscape conversion is occurring outside marine reserve recommendations and may not be a priority concern for managers. Connecting future management and conservation decisions to these change analyses will help protect the sustainability of the SWCMR’s diverse human-environment system.