Mangroves are ecosystems that are essential to coastal stability in the tropics, and in French Guiana in particular, where they cover almost 90% of the coastline. These coastal forests, which are home to a rich biodiversity and play a key role in the carbon cycle, are nevertheless the target of numerous anthropogenic and climatic pressures. Scientific studies are being undertaken to gain a better understanding of their natural establishment and expansion patterns.
Adrien Staquet, based in Cayenne since 2023, is working on these issues as part of a thesis funded by the PPR Ocean & Climate Priority Research Programme. His work is intended to address the need to improve mangrove planting and rehabilitation practices around the world. It is a concrete response to the need to find natural solutions for adapting populations to the major risks of coastal erosion that have already been observed.
Cover photo: Aerial view of the mangrove in French Guiana © Christophe PROISY/IRD/AMAP/CNRS Images
A wide range of multi-disciplinary skills at the service of tropical forest ecology
Adrien Staquet has long been fascinated by the great biodiversity of tropical forests, and in 2011 he left his native Lille. He obtained his first Master’s degree specialising in tropical forest ecology at the french Université des Antilles et de la Guyane.
In 2015, he continued his studies with a professional training course at the AgroParisTech institute, to obtain a master’s degree in international management specialisinǵ in the links between ‘Forest, nature and societý. It was there that he learned about project management and systemic diagnosis in a cross-disciplinary approach to issues.
But in 2020, the Covid pandemic forced Adrien to return to the north of France. He took up a new university course, this time at the University of Lille, to add to his CV a new master’s degree in ‘Functioning and management of marine ecosystems’.
© Adrien Staquet
Since the beginning of 2023, Adrien Staquet has been back in Cayenne. On the IRD Montabo campus, he is continuing his research with a thesis aimed at gaining a better understanding of the conditions under which mangroves are established in French Guiana. With several university degrees to his name, the young researcher sees this as an opportunity to mobilise all his multi-disciplinary skills by placing himself at the crossroads of forest ecology, marine ecology and social sciences applied to the environment.
Guiana’s coastline, a prime study area for understanding the natural functioning of mangroves
Located at the interface between land and sea, the mangrove is a unique forest system that grows and settles on the mud. The tree species that make up mangrove forests are many and varied, and are grouped together under the common name of mangrove. The diversity of these mangrove forest habitats therefore reflects a diversity of ecosystem functions.
In French Guiana, mangroves are subject to specific coastal dynamics. They are influenced by complex hydro-sedimentary processes, mainly driven by the dynamics of the Amazon, which lead to the formation of gigantic mud banks that are ideal for the development of mangroves. By absorbing the energy of the swells that reach the coast, these mud banks play a crucial role both in stabilising a coastline subject to erosion, and in the development of a varied local biodiversity hosted by the mangroves they shelter.
While urbanisation and human pressures on the Guiana coast are exacerbating the risks to these essential coastal forests, they are also known to renew themselves just as naturally as they can disappear under the effect of these mud bank movements. A phenomenon that is unique in the world!
Development of mangrove forests on mud banks in French Guiana © Adrien Staquet
The coastal regions of French Guiana are therefore favourable for attempting to characterise in detail the mechanisms of natural colonisation of mangroves on the coasts. What are the hydro-sedimentary processes that favour the natural establishment of mangroves? Are there environmental factors that determine this establishment, such as the height of mud, water temperature or salinity? And conversely, what are the modes of mangrove expansion (in terms of speed or spatial distribution, for example) in relation to these factors?
Answering these questions should enable better management of projects to restore or rehabilitate mangrove forests in French Guiana, and more widely in areas of the world where they are threatened or have even disappeared.
Innovative methods for monitoring mangrove development
To gain a better understanding of the interactions between ecological factors and coastal dynamics in French Guiana, Adrien Staquet is applying innovative methods to observe the formation of mud banks and collect data on the elevation of muddy substrates.
To do this, he uses advanced technologies such as laser remote sensing, spatial surveys and photogrammetric drone surveys to monitor the expansion of mangroves on recently formed mud banks. These observations help to identify the environmental factors that promote or limit the renewal of these ecosystems.
Point cloud of mangrove forests obtained from a LiDAR (Light Detection And Ranging) survey carried out by drone on the Guatemala mud bank, near Kourou. © Adrien Staquet
His thesis is being funded for 3 years by the PPR Ocean & Climate Priority Research Programme, as part of two challenges aimed at improving the protection and resilience of marine environments and developing new integrative management approaches, as well as forecasting the impacts of extreme phenomena linked to climate change in overseas France to guide regional policies.
Under the supervision of Christophe Proisy (UMR AMAP / IRD) and Antoine Gardel (UAR LEEISA / CNRS), this thesis aims to provide robust tools and indicators for coastal managers in French Guiana, and in the longer term to strengthen international strategies for the protection and sustainable management of mangroves in the face of the challenges posed by climate change and coastal erosion.
3 Questions to Adrien Staquet
Why did you decide to do a PhD in marine sciences?
Mangrove forests are at the heart of a huge number of socio-ecosystem issues because of the services they provide. So far, I have been able to develop my skills during my studies in tropical forest ecology and marine ecology by also tackling this aspect of ecosystems and their socio-environmental issues. This thesis is therefore very much in line with my studies and reflects my desire to delve deeper into this aspect of socio-ecosystem issues.
What made you want to do this thesis? What were your motivations?
In the long term, this thesis should help to identify the conditions required for the establishment of mangroves in an area, using a highly multidisciplinary approach. It is therefore a necessary research stage to learn how to effectively manage a mangrove restoration or rehabilitation project in areas where mangroves have unfortunately disappeared. So I’m very excited to be taking part!
How do you imagine your future after this thesis?
Of course, I’d like to continue working in the field of scientific research, as a post-doc, teacher-researcher or research engineer. If an opportunity arises, I’m also considering the possibility of working in an association to continue to take action on environmental and ecological issues.
Référence : Staquet, Adrien : « Climatic, oceanic and sedimentary conditions of the natural renewal of mangroves in French Guyana for an adaptive coastal protection strategy », thesis 2022-2025
Contact : adrien.staquet@ird.fr