Counteracting climate change in increasing carbon storage in coastal ecosystems

23 August 2021, by Leibnitz ZMT

Photo: M.Zimmer, ZMT

Mangroves in Brazil as part of a coastal ecosystem

Developing innovative and socially accepted approaches to improve the natural potential for carbon storage in vegetation-rich coastal ecosystems: that is the goal of the new research consortium sea4soCiety, coordinated by the Leibniz Centre for Tropical Marine Research (ZMT) in Bremen. Germany’s Federal Ministry of Education and Research (BMBF) is funding the consortium with 5.3 million euros as part of the first research mission “Marine carbon sinks in decarbonization pathways” – in short: CDRmare – of the German Marine Research Alliance (DAM). Beate Ratter and Kai Jensen from CEN take part in the new project.

As one of a total of six research consortia in the mission "Marine carbon sinks in decarbonization pathways", sea4soCiety will bring together almost 40 scientists from nine northern German universities and research institutes. Over the course of the three-year funding phase they will quantify and analyse the storage capacity for "blue carbon" in four different types of coastal ecosystems on the German North Sea and Baltic Sea coasts, in the Caribbean and the Indonesian Sea. Martin Zimmer, Head of the Department of Ecology at ZMT and Professor of Mangrove Ecology at the University of Bremen, is responsible for coordinating the research project.

Vegetation-rich coastal ecosystems of tropical and temperate latitudes, such as mangrove forests, seagrass beds, salt marshes or kelp forests, absorb huge amounts of carbon dioxide (CO2) from the atmosphere. Mangrove forests in tropical regions alone absorb 40 to 60 million tonnes of carbon annually. That is about as much as road traffic in Germany emits as greenhouse gases per year. The salt marshes of the Wadden Sea on the German North Sea coast store about 20,000 tonnes of carbon annually. The storage of this so-called "blue carbon" is one of the most important services provided by coastal ecosystems.

In recent decades, urbanisation, erosion or pollution have increasingly damaged the properties, processes and services of many ecosystems in coastal regions worldwide. Consequently, the global capacity to compensate for CO2 emissions by storing "blue carbon" in coastal ecosystems has also declined.

Designing ecosystems in a way they can resume their "services"

“We need concrete measures to counteract this trend so that coastal ecosystems can continue to contribute to climate change mitigation,” explains coordinator Martin Zimmer. “If these ecosystems can absorb more carbon dioxide, this will not only help mitigate the effects of climate change such as sea level rise and extreme weather events, but will also benefit biodiversity and productivity in coastal regions, which in turn can contribute to societal well-being and economic stability.”

The researchers will contribute scientific expertise in coastal ecology, chemistry, sedimentology, geology, hydrodynamics, remote sensing and modelling to quantify the storage capacity of "blue carbon" in seagrass beds, algae, salt marshes and mangrove forests and compare it with the depots of organic material in unvegetated marine sediments.

The origin, stability and dynamics of organic matter are analysed in the field and in the laboratories of the collaborative partners. Satellite data and ship-based measurements are used to determine the biomass on land and underwater in coastal zones. Communication with local societies, modelling and scenarios will make an evaluation of the potential benefits and risks of increasing the area of coastal ecosystems beyond their current stocks possible.

Considering the local needs for ecosystem services

“By characterising habitat conditions of coastal vegetated ecosystems, we can identify unvegetated coastal stretches that would be suitable for either expanding or creating new coastal ecosystems,” says Zimmer. “Ecosystem design, i.e. the targeted implementation of ecosystems for the restoration of ecosystem services, plays a central role in our approach to formulating recommendations for the future management of coastal ecosystems.”

According to the researchers, suitable measures should be ecologically feasible, environmentally compatible and legally and ethically unobjectionable. Natural scientists are working closely together with researchers from the fields of human geography, socio-economics, ethics and law in an interdisciplinary network to ensure that the approaches to improving carbon storage in coastal ecosystems meet societal requirements, create additional benefits and are based on broad acceptance.

Based on the results of socio-ecological studies, both a roadmap for the sustainable use of marine carbon reservoirs and evidence- and scenario-based recommendations for politics, the private sector and society will be developed. Based on local field research, these proposals will be extrapolated up to scales of national, international and global relevance.

“Thus, in an innovative and participatory approach, new governance pathways will be designed that take into account local needs for ecosystem services in addition to mitigating climate change by sequestering ‘blue carbon’," explains geographer Beate Ratter from the Center for Earth System Research and Sustainability (CEN) at the University of Hamburg.

“With its socio-ecological orientation, the project is embedded within the DAM research mission 'Marine carbon sinks in decarbonization pathways' in a multidisciplinary network to investigate natural science, technological, societal, legal and ethical aspects of different CO2 removal methods. Thus, sea4soCiety makes a further and very specific contribution to the overall goal of the mission,” says Gregor Rehder from the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) and one of the spokespersons of the research mission.

“By increasing the capacity of coastal ecosystems to sequester greenhouse gases and securing additional ecosystem services, the sea4soCiety research network contributes to achieving the goals of the Paris Climate Agreement, the United Nations Framework Convention on Climate Change (UNFCCC) and the United Nations 2030 Agenda,” Martin Zimmer concludes.