The importance of conservation for the provision of ecosystem services in flood control.

Climate change exacerbates natural disasters, primarily driven by environmental degradation, which leads to the reduction of available ecosystem services (ES). In this context, a comparative analysis of land use and land cover (LULC) and hydrological significance (HS) over a 30-year period was conducted to assess the loss of services in the Cubatão River Basin - SC, focusing on flood control. A matrix-based calculation was employed, integrating slope, transmissivity, soil texture, land use and cover, and the topographic wetness index to determine the hydrological significance of the study area. The urban area doubled in size (1992: 7.82% - 2022: 15.53%), while natural areas decreased by 5.3%. These natural areas, which still comprise over 50% of the territory, exhibit "Good" hydrological significance, covering nearly 40% of the total area and providing more than 15 ES. However, despite this favorable hydrological condition, the southern bay of Florianópolis suffered losses exceeding BRL 40 million in natural disasters of climatic and hydrological origin, in 2008. These findings highlight that, even with adequate hydrological performance, flooding events remain a threat. Thus, urban expansion planning, guided by municipal master plans that evaluate ES and the conservation of key areas for flood control, is essential to ensure social, economic, and environmental security.