Geographic visualization of land degradation risk in southeastern Brazil: A comprehensive assessment based on remote sensing and GIS

Research Background and Significance

Land degradation is a global environmental and socio-economic challenge, threatening ecosystem services, agricultural productivity, and sustainable development. In Brazil, particularly in regions undergoing rapid land-use transitions in the southeast, soil erosion is especially prominent. The state of Rio de Janeiro not only encompasses coastal metropolises but also contains remnants of the Atlantic Forest, farmland, and urban-rural interfaces in its hinterland, all of which are highly sensitive to degradation processes. This study integrates remote sensing, geographic information systems (GIS), and spatial multi-criteria analysis to assess and map land degradation risk in this region, providing a scientific basis for targeted land conservation policies.

Methods and Framework

The study adopts the framework of the United Nations Environment Programme Priority Actions Programme Regional Activity Centre (UNEP-PAP/RAC), combined with the latest high-resolution satellite imagery (Airbus 2025 imagery and Esri World Imagery), using maximum likelihood supervised classification for land use classification. The geospatial prioritization model integrates biophysical and socio-economic variables to identify conservation hotspots and support decision-making.

Key Findings

• Stability Classification: 68.4% of the landscape was classified as stable, primarily consisting of unmanaged land with agricultural and forest potential; 7.8% was classified as unstable, with sheet erosion concentrated in agricultural expansion frontiers.
• Priority Grading: 51.7% of the area was designated as "stable with medium priority," indicating widespread potential vulnerability; 4.6% was classified as "unstable with high priority," requiring urgent intervention.
• Land Use Change (1985–2024): Urban expansion reached 199%, while agricultural land decreased by 34%, highlighting the impact of anthropogenic drivers on degradation processes.

Implications for Infrastructure and Regional Development

Land degradation risk is directly linked to the long-term stability of infrastructure. For linear infrastructure such as transportation networks (e.g., roads, railways), port facilities, and energy pipelines, unstable land conditions can lead to foundation subsidence, slope instability, and soaring maintenance costs. The spatially explicit maps generated in this study can serve as inputs for environmental risk assessment in project financing, helping investors identify high-priority intervention areas. Moreover, the sharp increase in urban expansion suggests that future infrastructure planning must more rigorously incorporate land carrying capacity considerations to avoid large-scale development in high degradation-risk zones. This research framework can be extended to other tropical coastal regions, providing a methodological reference for environmental due diligence in infrastructure development across the Global South.

Conclusions and Prospects

This study validates the applicability of the PAP/RAC framework in humid tropical coastal environments and establishes empirical links between land use change and degradation hotspots. Its outputs—stability/instability classification maps and conservation priority maps—provide immediately usable tools for land management and sustainable development policies in Brazil. For global infrastructure analysts, such spatial data can help optimize investment portfolios, balancing development needs with environmental sustainability.