Evaluating the Efficacy of Small-Scale MPAs for Preserving Reef Health: An Application of ‘Structure from Motion’ Photogrammetry
Project
ID: 00000C437
Public
Human activity is having a global negative impact on species and habitats in aquatic ecosystems. In the oceans, marine protected areas (MPAs) are increasingly being used as a management mechanism to conserve individual species or entire systems at risk. Managers have particularly focussed MPA creation on biogenic reef environments, because of their importance as habitat for multiple species, their importance for human services such as food provision, and their fragility to disturbances such as intense fishing. However, due to a range of difficulties in enforcing and monitoring the effectiveness of MPAs, coastal developing countries, which often have large extents of tropical coral reefs and high dependence on their resources, appear to be lagging behind better resourced countries in terms of MPA management, leaving their reef areas at high risk of degradation. This study uses reef community data collected at three reserves within the heavily populated Western Visayas region of the central Philippines to assess the state of reef benthic structure inside and outside of small-scale locally managed MPAs. Physical structural data was captured through the use of recently developed ‘Structure from Motion’ photogrammetry techniques, allowing multiple quantitative metrics of physical 3D structural complexity and benthic health to be recorded. This new technology allows greater insight into the changes occurring at each site, and can be further matched to the community structure of associated fish species. Our results demonstrate the benefits of community run MPAs even when applied on a small scale of 10-20 ha, and show clear negative shifts in both the structure and function of un-managed reef communities. Mean fish biomass was shown to be five times greater inside protected sites relative to outside, with significant increases in both average body size and diversity metrics also seen. In terms of physical structure, mean 3D rugosity ratio increased from 3 to 6 between damaged and undamaged sites, and showed a concurrent increased mean reef height of >25 cm. These differences are seen to be related to a number of chronic and acute pressures from the surrounding human population, in the form of blast fishing and recent earthquake damage.