Are intertidal habitats keeping up with nutrient export? Insights from modelling climate and management scenarios

Habitat loss and eutrophication are major threats to estuarine systems leading to biodiversity decline and loss of ecosystem services. These stressors are particularly severe in estuaries situated in highly urbanised and agriculture-dominated landscapes. While several studies have assessed nutrient dynamics in estuaries, few have focused specifically on the role of intertidal habitats as buffer areas, highlighting the novelty of this study by assessing if nutrient retention abilities of buffer habitats are able to keep up with the high nutrient export from nearby land-uses. This study employs two InVEST models (Nutrient Delivery Ratio and Habitat Quality). Scenarios also employed different management strategies and climate-change simulations to assess alterations in nutrient export and habitat quality. Agricultural and grazing fields were the largest sources of nutrients into the system, while intertidal habitats, particularly saltmarshes, exhibited high nutrient retention rates (> 80 %). Nutrient export was most severely affected by management scenarios, particularly Business-as-usual and Ecological Protection, while no significant changes were observed in Climate-change scenarios. Contrarily, habitat quality declined under the Economic Development scenario. For example, filamentous algae lost 22.02 % of area under excellent conditions. Nutrient export remained unaffected by the Economic Development Scenario. Saltmarshes were consistently of high quality, while seagrasses were in poorer condition (less than 1 % of the seagrass area was under excellent conditions). This study also revealed that intertidal habitats are keeping up with nutrient export, however, the upraising impacts of climate and land-use changes require update management strategies that actively change the practices in the region. Insights from such modelling approaches can aid decision-makers, offering guidance for developing policies regarding conservation of natural habitats and sustainable agriculture practices.