Impacts of Tree Harvesting on the Carbon Balance and Functioning in Mangrove Forests.

Abstract

The importance of mangrove forests to the livelihoods of the local communities as well as to the ecological functioning of coastal ecosystems has been widely recognised. However, mangrove forests are at a high risk of being degraded and lost due to rapid growth of human populations and the economic pressures subjected to the coastal ecosystems. The implications of mangrove deforestation and degradation on the ecological functioning of these systems are far reaching and hence need to be investigated. This study experimentally explored the impacts of small scale cutting of mangroves on the functioning of the ecosystem. Secondly, it aimed to estimate belowground productivity of mangroves, as well as relating aboveground biomass production to belowground root production. Chapter one gives an over-view of the role of mangroves in carbon sequestration. Particular emphasis is given on the roles of mangroves in climate change mitigation and adaptation, as efficient carbon sinks, coastal stabilization and protection. The controls of carbon fluxes in mangrove forests as well as the impacts of deforestation on mangrove ecosystem functioning are explored. The patterns of mangrove productivity are also discussed. Chapter two experimentally explores the implications of small scale cutting on carbon fluxes in mangrove forests. The findings indicate that mangrove cutting can enhance additional C emissions of 9.8 ± 7.1 tCO2 ha-1 yr-1. Similarly, small scale cutting can also induce subsidence at the rate of -32 mm yr-1 within 2 years of cutting. Chapter three discusses the impacts of tree canopy removal on the biotic attributes of the mangrove ecosystems. The results show that removal of all vegetation can drastically affect the ability of the forest to rejuvenate. Furthermore, canopy removal significantly influences species composition of macrofaunal communities, whereby, gap-preferring species would colonize and dominate open areas created by canopy removal. Chapter four gives an insight on the patterns of mangrove forest productivity on a local scale. The findings indicate that even at a local level variation in forest productivity exists, probably due to micro topographic differences and soil factors. The results also confirm the high investment in belowground components. There also exist a possibility of significant relationship between above- and belowground biomass productivity. It is also shown that below-to-aboveground productivity ratios follow similar patterns to below-to-aboveground biomass ratios. Chapter five provides general conclusions of the preceding chapters putting the findings in line with the current trends in mangrove forest decline. The strategies of reversing mangrove decline are also suggested, including the financial initiatives such as Payment for Ecosystem Services (PES) schemes through strategies such as Reducing Emissions for Deforestation Degradation (REDD+). Finally, a number of recommendations are given including sound management options and further issues arising from this study.