Sebrian Beselly earns PhD for research that can help mangrove restoration succeed

For my PhD research, I developed a new modelling tool, DFMFON, that is capable of simulating mangrove forest growth, retreat and colonisation, including the forest’s interactions with the environment. I created the tool by combining an individual-based mangrove model and a landscape-scale hydro-morphodynamic model. With this novel approach, we can follow individual mangrove tree life stages: we can see how the mangrove develops from propagule to seedling, to sapling and to adult tree.  We can also see how the mangroves’ establishment, growth and dieback are influenced by – while also influencing - changing tides, waves, river flows, sediment availability and salinity.

As a case study, I investigated 11 years of mangrove and delta dynamics in the Porong Delta in Indonesia. I developed a technique that uses multiple sources of satellite and drone images. Next, I developed a complex eco-geomorphic mangrove-mudflat model and validated the simulation based on observations in Porong Delta. The model successfully reproduced my observations in terms of mangrove development over time, including the age-height relationship and morphodynamic delta features. Finally, I demonstrated that the model has the capability to optimize the design of mangrove restoration strategies so that they capture as much greenhouse gases as possible for climate mitigation.

I had to use a combination of field and computer modelling skills for my research. Both bring their own challenges. Mangrove wetlands are not easy places to do fieldwork: it is difficult to walk on muddy coastlines - especially when you and the equipment can constantly sink! Walking in the mud is an acquired skill. I made my own ‘surfboard’ made of thrown-away styrofoam to slide on the mud.

I understood from the start that my research would involve a lot of coding as part of the modelling work. I started with zero programming skills and dedicated long hours to learn and understand MATLAB, Python, Java and eventually JavaScript. COVID-19 also was a challenge as the planned fieldwork activities had to be delayed. I finally managed to do my second fieldwork, almost not being able to fly back to the Netherlands due to the outbreak of the Delta variant.

My supervisory team played a crucial role in helping me to overcome the technical challenges I encountered. They suggested courses that helped me to learn new programming skills. They helped me overcome COVID-related funding challenges with suggestions on grants and support for successful fieldwork.

All the stories were stitched together into a meaningful and glorious moment when I was honoured with the Syvitsky Student Modeler Award at the Community Surface Dynamics Modeling System (CSDMS) meeting in the United States  in May 2024. The award honours innovative model development that demonstrates ingenuity, applicability, and contribution toward the advancement of geoscience modelling.

We have global commitments to cut greenhouse gas emissions by 45% by 2030, and by that same year, the global mangrove cover should have increased by 20% as compared to the 2021 level, according to commitments made in relation to the UN Decade of Ecosystem Restoration 2021-2030. There’s less than six years to 2030 - we need prompt actions! My research provides an improved understanding on how to strategically conserve mangrove forests to contribute to climate mitigation and adaptation.

I am thrilled to contribute to capacity development and research in coastal and urban hazards and risks at IHE Delft and in Indonesia.

If I could tell myself something when I started my PhD, I would say: you are not alone in this journey. You have your supervisory team and your fellow PhD candidates. Do not hesitate to seek guidance and support. Appreciate and celebrate every achievement you have made. They may look small but are an important foundation of your work.

The title of his thesis is: The Mangrove Tale: Mechanistic Modelling of Mangrove-Eco-Geomorphic Interactions

Mangroves are acknowledged for their wide range of ecosystem services. As such, mangrove conservation has been considered one of the top priorities within coastal communities worldwide. Despite global commitments and support from countries and international organisations, the majority of mangrove restoration projects have been reported to fail.

This study aims to develop a better understanding of complex eco-geomorphic interactions and feedback processes in the evolution of coastal mangrove environments. A newly developed model (DFMFON) resolves the feedback processes between hydro-morphodynamic forcing (waves, tides, river flow, sediment supply, salinity, and morphodynamics) and mangrove life stages ranging from (dispersal of) propagules to the development of seedlings and sapling into mature trees.

The model successfully reproduces observed spatiotemporal (seasonal-decadal) mangrove development, like the age-height relationship, as well as morphodynamic delta evolution in Porong Estuary, Indonesia. The model is then used to optimize mangrove restoration strategies and carbon sequestration capacity in coastal systems. The case study observations and tool presented in this thesis open up possibilities for optimising mangrove restoration management schemes for climate mitigation and adaptation in sustainable coastal systems.