AbstractMangrove forests are extremely productive ecosystems that continue to be degraded and destroyed in many parts of the world, principally through conversion to aquaculture ponds. Compounding the loss of ecosystem services that healthy mangroves provide is the substantial portion of existing aquaculture ponds that are now in a state of either disuse or complete abandonment, particularly in Southeast Asia. The rehabilitation of disused aquaculture ponds, in contrast, represents an opportunity to restore and regain the array of ecosystem services mangroves provide. Utilising forest carbon markets is potentially an attractive avenue to help finance rehabilitation projects given mangroves store and sequester disproportionally high levels of carbon per unit area compared to other ecosystems. However, significant data gaps remain in understanding carbon dynamics and the resultant greenhouse gas (GHG) emissions reductions associated with mangrove rehabilitation projects.
This project helps address knowledge gaps through the quantitative assessment of (a) community structure, carbon storage and sequestration gains, and (b) GHG flux from mangrove sites which had undergone ecological mangrove rehabilitation (EMR). Disused aquaculture ponds and mature reference forests were also assessed to enable comparisons across a spectrum of land use, land-use change and forestry (LULUCF). These data were used to derive estimates of both baseline GHG emissions (GHGbase) from aquaculture ponds as well as the mitigation benefits resultant from rehabilitating mangrove forests (GHGrehab).
The carbon sequestration and GHG effluxes from EMR sites in Tiwoho, North Sulawesi were quantified and these sites potentially mitigate upwards of 27.4 ± 1.8 Mg CO2 e ha-1 y-1. Components of this shift in emissions include a GHGbase of +17 ± 0.8 Mg CO2e ha-1 y-1] minus GHGrehab of -10.4 ± 1 Mg CO2e ha-1 y-1 (negative value denotes a net sink). The potential GHG mitigation benefits on at ha-1 y-1 scales from Tiwoho’s EMR sites is upwards of 3 times that of other terrestrial biomes more typically associated with Afforestation / Reforestation and avoided deforestation projects. Additionally, we found that Tiwoho’s rehabilitated sites may have offset on average 76.2% of the initial project implementation costs in just 10 years, rivalling that of traditional asset classes advocated for private sector investment. High productivity sites returned 93.7% after 10 years, with all further sequestration over time in excess of the initial investment costs. These results are valuable in strengthening the evidence base needed to galvanize public and private sector support for investment in mangrove rehabilitation through utilising forest carbon markets.
|Date of Award||Oct 2018|
|Supervisor||Lindsay B. Hutley (Supervisor)|