Rehabilitating mangrove ecosystem services: A case study on the relative benefits of abandoned pond reversion from Panay Island, Philippines

Study Number

91

Author:

Clare Duncan, Jurgenne H. Primavera, Nathalie Pettorelli, Julian R. Thompson, Rona Joy A. Loma, Heather J. Koldewey

Abstract

Mangroves provide vital climate change mitigation and adaptation (CCMA) ecosystem services (ES), yet have suffered extensive tropics-wide declines. To mitigate losses, rehabilitation is high on the conservation agenda. However, the relative functionality and ES delivery of rehabilitated mangroves in different intertidal locations is rarely assessed. In a case study from Panay Island, Philippines, using field- and satellite-derived methods, we assess carbon stocks and coastal protection potential of rehabilitated low-intertidal seafront and mid- to upper-intertidal abandoned (leased) fishpond areas, against reference natural mangroves. Due to large sizes and appropriate site conditions, targeted abandoned fishpond reversion to former mangrove was found to be favourable for enhancing CCMA in the coastal zone. In a municipality-specific case study, 96.7% of abandoned fishponds with high potential for effective greenbelt rehabilitation had favourable tenure status for reversion. These findings have implications for coastal zone management in Asia in the face of climate change.

Main Results and Conclusions

• Mangrove habitat loss is a major problem on Panay Island, and this study aims to evaluate the potential for rehabilitating abandoned fishponds and restoring mangroves in those areas. The study also assesses the effectiveness of rehabilitation in cultivating the climate change mitigation and adaptation (CCMA) ecosystem services that mangroves provide.
  • “Reversion of abandoned fishponds to former mangroves for greenbelt resurrection could thus benefit coastal community livelihoods through associated fisheries enhancement” (773)
  • “While per hectare carbon stocks were variable across both rehabilitated and natural areas, rehabilitation for enhanced CCMA goals appears more promising in abandoned fishponds. Despite currently lower per hectare biomass production, carbon-rich sediments and large areal coverage enhanced the overall carbon stocks and coastal protection potential of rehabilitated abandoned fishponds” (779)
• Abandoned fishponds showed a greater potential for restoring the CCMA services of mangroves than other sites, and did not differ significantly from natural, unrestored mangrove sites.
  • “The abandoned fishponds were either not different (Nabitasan) or had significantly greater (Dumangas) plot-level sediment carbon stocks than natural areas, and greater than seafront rehabilitated areas. This reflects their position on former mangrove sediments, and highlights their greater potential over seafront rehabilitation sites” (779)
• These results are particularly important for countries that are typhoon-prone and are likely to abandon fishponds in a similar manner.
  • “mangrove rehabilitation may have particular relevance elsewhere in South and Southeast Asia where fishpond abandonment is similarly high: e.g. Malaysia (60%; Choo, 1996), Sri Lanka (60-90%; Jayakody et al., 2012; Bournazel et al., 2015). In other, more typhoon-prone countries believed to have high rates of fishpond abandonment (e.g. Vietnam, Taiwan; Stevenson, 1997), the potential CCMA benefits of abandoned pond identification and rehabilitation may be of particular consequence” (780-781)