Analysis of the impact on vegetation along wetlands of changes in groundwater levels due to climate change. The Flemish Kalkense Meersen case study. =

This research focuses on the effects of climate change on water levels fluctuations and, as a result, on wetlands. The majority of climate models predict that climate change will primarily impact extreme events, leading to an increase in the frequency and intensity of both droughts and floods, and so to higher peak flows and deeper low flows. The study aims at investigating how this anticipated impact will affect the well-being of wetland ecosystems over different scenarios. Wetlands are globally recognized as ecosystems that serve vital ecological functions and hold significance as cultural and natural heritage sites. The specific wetland under examination is situated along the Flemish Sigma Plan, within the Kalkense Meersen Cluster, in Belgium. The Sigma Plan is a network of flood control areas established along the Scheldt River since 1976. This river naturally experiences tidal influence from the North Sea, allowing extraordinary natural growth along its banks but also posing a significant flood risk to adjacent areas. The Sigma Plan was initiated with the dual objective of protecting the land through water regulation and restoring the unique vegetation along the riverbanks. The Research Institute for Nature and Forest (INBO) has compiled a list of target habitats with high ecological value, found in the Sigma areas, including the Kalkense wetland, crucial for preservation and establishment under varying climatic scenarios. The work consists in an analysis of the actual summer groundwater levels of the wetland, expected to be the most impacted by climate change. These levels are estimated through hydrological conceptual models, run for three different scenarios, namely current, future without water-management and future with water-management to contrast climate change, and compared with the ideal ranges of groundwater required by each habitat as designated by the Niche model for Flanders. The latter is an important Flemish eco-hydrological tool that offers insights into the ideal abiotic conditions for groundwater-dependent ecosystems. The comparisons are visualized through spatial maps with a resolution of 10x10 meters, where each pixel is color-coded according to its actual water level condition relative to the ideal one. The results show that, under the current scenario, many habitats are in optimal conditions, while others are more at risk because closer to critical values. Conversely, a future scenario without management demonstrates that failing to take action against climate change results in a decline in aquifer storage and subsequent deterioration of conditions for many habitats. On the contrary, a future scenario with artificial hydrological management demonstrates the potential to restore current conditions. Finally, the study identifies alternative water-management actions that could yield economic and ecological advantages, compared to the current condition.