Plant engineering is increasingly being used to restore riverbanks that have been heavily degraded by human activity. Already widely used in Europe and mainland France, the technique is now being introduced in Guadeloupe, where scientists are facing new challenges.
Riverbanks fulfill essential ecological functions, such as providing habitats for biodiversity and encouraging movement of plant and animal species. They also provide protection against floods, clean the water and provide economic and social services (landscapes, leisure activities, etc.). Nevertheless, today, these environments have been heavily degraded by the human activity and infrastructure around them.
Plant engineering involves using plants to stabilize these banks. It is used to preserve banks against erosion and therefore protect housing and infrastructure, in a similar way to civil engineering structures (rock filling, concreting, etc.), as well as to restore their ecological functions.
Increasingly common in Europe, the technique is now being introduced in Guadeloupe through the Protéger project which aims to restore the riverbanks of this Caribbean island. Irstea, Inra, the Université des Antilles and their partners are working on the project, which is led by the Guadeloupe National Park.
“This is a comprehensive project that incorporates everything from descriptions of natural models to commercial transfers,” explains André Evette, researcher at Irstea Grenoble and a recognized expert in the field. “Addressing social as well as environmental issues, it will help us develop plant nurseries and train professionals.”
Guadeloupe: a unique context for plant engineering
Although plant engineering techniques are well established in French mainland rivers, this is not the case in Guadeloupe. Scientists are facing several difficulties specific to tropical ecosystems, such as high flood intensities, significant gradients, sediment transport and erosion. Additionally, banks in downstream areas are heavily urbanized.
“These areas are biodiversity hotspots and have high levels of endemic species (species only found here). However, these fragile plants are being homogenized. As part of this project, we want to use local plants, to resolve key biodiversity conservation issues,” concludes Evette.
Natural models for Guadeloupe are poorly understood and local experiences of plant engineering are practically nonexistent. Scientists therefore have to reimagine plant engineering, from the choice of species to the techniques used.
Implementing a sustainable plant engineering process
The first stage in the project is to describe natural models and select local species that are most adapted to maintaining the riverbanks. To this end, 30 species have been chosen using a variety of criteria, including dense root systems, flexible stalks, rapid growth and potential for propagation. The rare and indigenous nature of the plants was also taken into account.
The plants selected were planted in pots and their mechanical properties and biological characteristics were studied by project scientists. In partnership with the Guadeloupe Region, work sites will be created along rivers on the island to test the effectiveness of these plants in real conditions. “Riverbank protection work in Guadeloupe is increasingly taking plant engineering into account,” explains Evette. It will put the various types and techniques of plant engineering to the test.”
The work will also be used to understand and manage the reproductive capacity of the selected species and will provide the technical knowledge needed to grow them in nurseries.
Protéger project spearheading plant engineering in the Caribbean
The long-term aim of the project is to develop a local socioeconomic plant production process that uses environmental engineering techniques. A methodological guide to plant engineering will be published in due course. “Local stakeholders, companies, communities, etc. will be trained to use plant engineering techniques and create routine work sites to ensure a sustainable transition from civil engineering techniques to environmental engineering, which is reliable and respects the unique biodiversity of the region.” This project will lay the foundations for plant engineering in the Caribbean and aims to be an example and create the knowledge required for these methods to applied across the region.