Environmental Fragility and the Effect of Extreme Climate Events: the Relationship Between Vegetation Cover and Floods in the Guaíba Hydrographic Region, Brazil

Extreme rainfall and floods in May 2024 caused the most severe natural disaster ever recorded in Rio Grande do Sul, Brazil, exposing systemic socio-environmental vulnerabilities. This study analyzes the loss of natural vegetation in the Guaíba Hydrographic Region (GHR) — a territory of major demographic, economic, and ecological importance — and its implications for territorial resilience. The GHR, marked by the transition between the Atlantic Forest and Pampa biomes, combines urbanized areas, agricultural frontiers, and sensitive ecosystems, making it a strategic case for understanding the interactions between land-use change, ecological fragmentation, and hydrological impacts. Using MapBiomas Collection 10 data (2023–2024), flood extent mapping from UFRGS, and a standardized hexagonal grid (2 km), we calculated vegetation loss, gain, and landscape metrics (patch size, edge, shape index, core area, proximity). Spatial analysis employed local bivariate Moran’s I (LISA) to identify clusters of high and low vegetation dynamics. Results show a 12.2% reduction in forest formations and significant fragmentation, with increased number of patches and greater distances between them. Low-gain/high-loss clusters were almost twice as frequent in flooded areas, indicating heightened vulnerability. Areas with greater vegetation continuity exhibited lower relative losses, suggesting that ecological connectivity is a key factor for mitigating flood impacts. Overlap with the most affected municipalities reinforces that vegetation suppression intensified damages, corroborating literature that links disasters to socio-territorial inequalities. The findings highlight that resilience depends not only on vegetation quantity but also on its spatial distribution and connectivity. Integrated territorial governance, ecological restoration of floodplains, and prevention of risk-area occupation are urgent to reduce future disaster impacts. This study contributes empirical evidence for planning and conservation policies aimed at enhancing socio-ecological resilience in multifunctional territories of the Global South.