Co-constructing and simulating LUCC scenarios for evaluating the sustainability of environmental policies and supporting long-term decision-making

Urbanization and agricultural intensification are major drivers of biodiversity loss due to multiple stressors, including land artificialization, habitat fragmentation, isolation, and degradation. These land-use and land-cover changes (LUCC) also impact water quality, carbon sequestration, and ecosystem services. Designing Blue and Green Infrastructure Networks (BGINs) has been proposed as a strategic approach to land-use planning that enhances ecosystem services while preserving biodiversity and improving water management. This study focuses on the Couesnon watershed (Brittany, France) within the LTSER Zone Atelier Armorique (https://deims.org/31e67a47-5f15-40ad-9a72-f6f0ee4ecff6). A participatory approach was employed to develop five future LUCC scenarios incorporating BGINs. Narrative descriptions were then used as input for the FORESCEM model to simulate LUCC dynamics (Fig. 1 - Houet et al. 2022). The impacts on biodiversity were assessed by evaluating changes in landscape connectivity for woodlands, grasslands, and wetlands using the model developed by Boussard et al. (2020). Additionally, the effects on water quality and quantity were analyzed under LUCC and RCP8.5 climate change scenarios using the model developed by Álvarez-Cabria et al. (2016). The effectiveness of BGIN policies was assessed by comparing current landscape connectivity (2018) with projected connectivity in 2050 and by estimating future water quality. Results indicate that despite integrating BGINs, the projected impacts on biodiversity (Fig. 2) and water resources could still be significantly negative. Key drivers of future agricultural land-use changes and related environmental impacts include evolving CAP priorities, demographic trends among farmers, and climate change. While BGINs are effective in mitigating urbanization impacts, they may not be sufficient at the landscape scale. This study highlights the necessity of systemic environmental policies that foster synergies among different administrative services involved in land management. The current sectoral (or "siloed") organisation levels remain a barrier to achieving land sustainability goals. While LUCC simulations are designed to assist decision-makers in implementing sustainable policies, we examined whether our results effectively support local stakeholders in the Couesnon watershed. We conducted 14 public meetings involving nearly 150 participants, including farmers, policymakers, land and resource management professionals, and students. Surveys and interviews conducted during the meetings and 6 to 12 months later revealed that while scenario-based approaches can influence decision-making, their impact requires time to materialize (Rigo and Houet 2023, Rigo et al. 2024). These findings underscore the need for further research and the importance of effectively communicating scientific insights to support the understanding, monitoring, and sustainable management of socio-ecological systems within the critical zone.