TRICMA²: Triple Crisis Meets Trilateral Cooperation

- Authored by TRICMA² -

Facing the triple crisis of biodiversity loss, climate change, and pollution, Wadden Sea salt marshes are under increasing pressure. TRICMA² (full title: Triple Crisis Meets Trilateral Cooperation - Effects of biodiversity loss, climate change and pollution on salt marshes & pathways to their sustainable management) will analyse effects of the triple crisis on ecological networks, ecological connectivity, and ecosystem functioning in salt marshes across the Wadden Sea. TRICMA² aims to identify pathways to a sustainable salt marsh management contributing to the Outstanding Universal Value of the Wadden Sea. We combine field observations with experiments where climate, biodiversity, and pollution are manipulated and the impacts on vegetation, soil fauna, and carbon cycling are analysed. Ecological connectivity will be investigated via movement patterns and habitat use of birds and their available food sources. TRICMA² includes a strong societal component by joint activities of scientists and stakeholders from several socio-economic sectors, including nature conservation, coastal protection, agriculture, and tourism. Youth will be involved in our research, drawing the attention of ‘future generations’ to ecological pressures to Wadden Sea ecosystems. Based on acquired stakeholder knowledge, novel scientific insights, and dedicated attention of ‘future generations’, TRICMA² will develop a set of guiding principles and priorities for sustainable Wadden Sea salt marsh management.

With four tightly interconnected work packages (1: Social-Ecological Learning; 2: Ecological Networks; 3: Ecological Connectivity; and 4: Ecological Functioning), TRICMA² address distinct questions related to salt marsh functioning and management by acknowledging both societal and scientific aspects of the ecosystem. Based on input from stakeholder interactions, we selected field sites and designed specific ecological experiments. This approach directly applies stakeholder expertise to guide feasible and scientifically relevant research questions. Our project is designed in such a way that data can be used by different work packages. For example, in-depth soil analysis of carbon, nutrients and pollutants is used to explain observed patterns in communities of microbes, plants, and invertebrates. Furthermore, identifying and counting macrozoobenthos at foraging locations for GPS-tracked targeted bird species gives insight in the diet of these birds and allows us to make future predictions on changes in utilisation patterns in response to global change.

In the following sections, we give some more insights in the four work packages.

WP1: Social-Ecological Learning

The work package engages in science-society interactions to facilitate societal impact. These science-society interactions have so far involved consultations with a diversity of stakeholders related to salt marsh management in the Wadden Sea. These consultations were organised with the explicit focus on entering the complex arena of the environmental, socio-economic, and political perspectives of Wadden Sea salt marsh management, and aim to give insight into diverse experiences and narratives that are crucial to our understanding of current and future salt marsh management. Preliminary analysis of stakeholder consultations has cemented youth as an important, yet previously overlooked demographic of stakeholders. Exploratory research is taking place on how to engage youth in the TRICMA² research, by linking with already established youth-oriented organisations. Furthermore, stakeholder consultations are being carefully deliberated amongst other collaborating Wadden Sea projects to develop coordinated activities that may reduce stakeholder fatigue.

WP2: Ecological Networks

The work package uses field contrasts and experimental facilities to analyse the effects of climate change and biodiversity change on the structure and interaction strength of ecological networks in salt marshes. We study networks of plants, microbes, benthos/soil fauna under different scenarios for temperature and/or flooding and/or pollutants. In field contrasts in all three Wadden Sea countries, we investigate differences between patches dominated by the native Salicornia europaea agg. and the non-native Spartina anglica. We also look at the difference in ecological networks and ecosystem functioning between areas with a high plant species richness (grazed by livestock) and areas with lower plant species richness (non-grazed areas). Preliminary results indicate that high plant species richness correlates with lower numbers of detritivore invertebrates. The controlled in-situ warming experiment MERIT provides valuable insights into how temperature rise alters structural and functional interactions within salt marsh ecosystems. Previous results indicate that warming exerts only minor effects on general plant parameters, however a slight shift of root biomass towards deeper soil layers was observed in the high marsh. Also, first insights into the effects of warming on methane fluxes and microbial communities indicate differences between the elevational zones and temperature scenarios. A mesocosm experiment at AWI (Sylt) focused on interactions between two dominant salt marsh species of the pioneer zone (Salicornia europaea agg. and Spartina anglica), microbial communities and the bioturbating ragworm Hediste diversicolor under stress conditions induced by a (marine) heatwave. The analysis of the collected data within MERIT and the mesocosm experiment is ongoing and is expected to provide new insights into how salt marsh communities may respond and adapt to future climate change.

WP3: Ecological Connectivity

We caught individuals of the five focal bird species central to the TRICMA² project: Brent Geese (Branta bernicla), Barnacle Geese (Branta leucopsis), Pied Avocets (Recurvirostra avosetta), Common Shelducks (Tadorna tadorna), and Eurasian Curlews (Numenius arquata). The respective animals were equipped with solar-powered GPS data loggers which enables the acquisition of high-resolution spatio-temporal tracking data used to address research questions on the selection and connectivity of various Wadden Sea habitats on several spatial scales (flyway-scale, landscape-scale, patch-scale). Regarding the habitat use of Barnacle Geese on the landscape-scale in the coastal zone of the Schleswig-Holstein Wadden Sea, first results indicate the geese’s preference for salt marsh habitats compared to open water/intertidal flat regions and the coastal hinterland. Additionally, the intersection of tracking data with highly precise geospatial vector data gathered as part of the Trilateral Monitoring and Assessment Programme (TMAP) revealed that within salt marsh habitats, Barnacle Geese preferentially utilise intensively grazed areas compared to those that are ungrazed or extensively grazed. Preferred salt marsh zones are the low marsh and the pioneer zone as well as salt marsh systems with fresh grasslands. Next to these habitat analyses, which will be extended during the upcoming months, feces from all five bird species were collected for an assessment of the birds’ contamination with micro-plastics and other pollutants.

WP4: Ecological Functioning

We assess biophysical and biogeochemical processes of accretion, greenhouse gas cycling, and pollutant retention in salt marshes. Measurements of greenhouse gas fluxes alongside other parameters have been performed in the abovementioned mesocosm experiment at AWI Sylt. Preliminary data from these measurements suggest strong effects of climate change and plant community composition on greenhouse gas dynamics. In addition, plots in field contrasts (Salicornia vs Spartina; high plant species richness vs low plant species richness) have been established for measurements of accretion. Furthermore, an initial exploratory screening of pollutants in salt marshes has provided insights into the ecological significance of specific pollutants like heavy metals and pesticides. Pesticides in salt marsh vegetation and soil will be further investigated in collaboration with colleagues at RPTU in Landau and linked to future investigations of microplastic pollution in birds.

Impressions