Environmental vulnerability applied to the territorial planning of a tropical semiarid basin.

Tropical semiarid regions are naturally prone to environmental damage. Human activity can worsen this situation. To understand how human actions affect the ecosystem, plan land use effectively, and establish targeted management practices, assessing environmental vulnerability is crucial. This study focuses on a sub-basin receiving water transfers from the São Francisco River in Brazil's semiarid region. Here, we map and evaluate how land use and occupation alter natural vulnerability. We also propose zoning strategies to support water resource management and implement sustainable development policies in the region. To achieve this, we conducted an integrated analysis of physical factors (soil types, geology, climate, vegetation, and landforms) and spatial land-use data using geographic information systems (GIS) and map algebra techniques. Map algebra allowed us to combine these various datasets within the GIS environment, enabling the creation of maps that synthesize both natural and environmental vulnerability across the study area. Following analysis of these vulnerability maps, our findings reveal a high level of vulnerability. The areas with high to very high degrees of natural vulnerability coincide with the places that have high slopes, high altitudes, Lithic Neosols, and thick vegetation. Furthermore, the interaction between environmental factors and human activity exacerbates vulnerability. Based on the environmental vulnerability assessment, we defined four environmental management zones. These zones require distinct protection measures and management approaches. As a method to potentially improve the basin's vulnerability scenario, soil conservation measures are recommended. This approach is highly relevant for managing land in tropical semiarid regions and, with adaptations to specific regional factors, can be applied globally.

Urbanization increases the risk of phosphorus loss in sandy soils of tropical ecosystems.

Phosphorus (P) is naturally present in soils. However, urbanization can promote additional inputs of P into the soil that lead to saturation of the binding sites exceeding the maximum sorption capacity. Soils saturated with P act as important diffuse sources of pollution of water resources. The flow of P from the soil to aquatic ecosystems is an aggravating factor for water scarcity, especially in the semiarid region. Knowing phosphorus dynamics in the soil is essential to protect water quality and ensure its multiple uses. In this paper, a total of fifty soil samples, twenty-five from natural soils and twenty-five from urban soils, were evaluated for the effect of urbanization on P sorption characteristics and their relationship with the physical and chemical attributes of the soil. The soil samples were characterized physically and chemically, and the P sorption characteristics were obtained from the adjustment of Langmuir and Freundlich equations by nonlinear regression. Urbanization results in increased soil P saturation and reduced P sorption capacity. Our results show that the sandy texture of the soils studied had a standardizing effect on the soil's physical properties, maintaining, even after urbanization, the physical quality similar to natural soil. In contrast, pH (in water and KCl), base saturation, sodium saturation, potential acidity, exchangeable Al3+, exchangeable Mg2+, available P, and P-rem are valuable indicators in the segregation between natural and urban soils. The reduction of P sorption capacity in urban soils increases the risks related to P loads in aquatic ecosystems that experience urban expansion worldwide. These data serve as a basis for decision-making regarding the appropriate soil monitoring and management of urban expansion areas in watersheds to control P flow to aquatic systems.