The Mangrove Tale

Abstract

The over-exploitation of mangrove forests since the 1980s has led to biodiversity loss and coastal erosion in several parts of the world. Still, about 80-90% of mangrove restoration projects have been reported to fail. The main reasons are related to a poor understanding of the eco-geomorphological dynamics and mangrove species-specific ecological requirements. Although several guidelines are available, they are mostly site-specific, with a management focus on coastal protection schemes. A better system understanding of the feedback processes between mangrove forests and mudflat dynamics is required.
The thesis objective is to gain a better insight into complex eco-geomorphic interactions and feedback processes in coastal mangrove environments to the benefit of developing trustworthy tools for predicting their dynamics. To achieve the objective, the thesis describes the development of hybrid modelling by coupling the landscape-scale processbased hydro-morphodynamic model Delft3D-Flexible Mesh (DFM) and the individualbased MesoFON mangrove model (MFON). This coupled model (DFMFON) resolves the feedback process between seasonal and decadal environmental changes (waves, tides, river flow, sediment supply, salinity, and morphodynamics) and mangrove life-stages ranging from (dispersal of) propagules to development of seedlings and sapling into mature trees.
Since it covers a unique, rapidly progressing delta setting with concomitant mangrove expansion, Porong Estuary in Indonesia is used as a case study to validate the newly developed modeling tool (DFMFON). Imagery from off-the-shelf unoccupied aerial vehicles (UAV’s) and atellites was used and groundthruthed to retrieve accurate mangrove structural attributes and mangrove belt dynamics. The DFMFON model successfully reproduced observed spatiotemporal (seasonal-decadal) mangrove development, like the age-height relationship, as well as morphodynamic delta features.
DFMFON was then used to explore optimizing mangrove restoration strategies and carbon sequestration capacity in coastal systems. Best results were obtained for higher level (above mean sea level) and patchy mangrove restoration schemes.
The observations and tool presented in this thesis open up possibilities to assess and gain a better system understanding of the interactions between mangroves and environmental drivers. DFMFON will be a helping hand in directing mangrove management schemes for climate change mitigation and adaptation.