Bio-morphodynamics of coastal wetlands with mangrove vegetation

Abstract

Mangroves are valuable coastal ecosystems that support and protect the lifes and lifelihoods of people across the tropics/subtropics. They predominantly grow at muddy shorelines, where their trunks and numerous aerial roots protect the coasts against erosion. Rising sea levels, reduced sediment availability, land-use change and widespread mangrove clearance are the primary threats to not only mangrove coverage but also the stability of the coastal landscape. Since the complexity of underlying mechanisms controlling mangrove ecosystems makes it difficult to predict mangrove evolution and devise management regimes, we are in dire need for improved process-based knowledge. This PhD thesis fulfills this need, through a bio-morphodynamic computer model developed to predict decadal and centennial mangrove- and coastal dynamics in response to changes in the coastal environment. The model shows that the balance of sea-level rise and sediment supply is a main determinant in predicting changes in mangrove coverage and diversity. Different coastal environmental conditions create distinct mangrove behaviors in response to rising sea levels. Inland dikes and barriers may constrain mangrove inland migration under sea-level rise, reducing their coverage and diversity. However, increasing fluvial sediment supply resulting from land-use change upstream stimulates mangrove expansion. Modelling shows that the coastal management strategy of mangrove clearance does not restore previously existing sandy flats but might precipitate an even muddier system. My results suggest that effective coastal management needs to consider a system approach and non-linear interactions between mangrove forests and their coastal environment.