Habitat Risk Assessment for the Tidal Marshes and Flats of Huildad Bay, Isla Grande de Chiloé, Chile

Abstract

The tidal marsh and tidal flats in the intertidal zones of Chiloé, Chile are highly productive ecosystems that provide essential ecosystem services and preserve local biodiversity. However, they face increasing pressure from human activities. This study evaluated the cumulative risk of habitat degradation in Huildad Bay using the InVEST Habitat Risk Assessment (HRA) model. This study integrated spatial data on key stressors, including aquaculture, urban infrastructure, and road networks to develop the first high-resolution risk maps for these two coastal habitats. Rather than presenting a comprehensive assessment of the total cumulative anthropogenic risk for Huildad Bay, cumulative risk percentages are represented using selected stress factors that were geospatially mapped for this study. The results revealed a significant cumulative risk, with approximately 22% of the total area classified as medium risk. High-risk hotspots are minimal but ecologically critical (0.36% in tidal flats and 2.50% in tidal marshes) and strictly confined to the shoreline interface. An uncertainty interval analysis using Monte Carlo simulations (500 runs) quantified the parameter uncertainty of these estimates. Qualitative field corroboration using drone imagery visually identified physical proxies of degradation, such as hydrocarbon sheens, in model-predicted medium- to high-risk zones near the fishing pier. This research provides a defensible, spatially explicit risk-screening tool for local authorities. The findings highlight the urgent need for targeted management strategies, early-warning monitoring, and evidence-based public policies to ensure the long-term resilience and sustainability of these vulnerable coastal ecosystems.