Understanding and managing nutrient pollution in peri-urban wetlands: The Ciénegas del Lerma, Mexico

Nutrient pollution has been broadly studied in developed countries, where the primary source is often agricultural diffuse pollution. However, more research is needed in developing countries with a predominance of low-income households, insufficient public service infrastructure, pressure from urban expansion, and scarce information. In this research, centered on the Lerma Cienega protected wetlands in a peri-urban area of Toluca city in Mexico, a socio-ecological systems framework was applied to study the nutrient pollution problem and recommend nutrient control measures. An export coefficient model was developed to estimate nutrient losses from micro-basin areas discharging to the wetlands, which range from 0 to 32 tonnes/year for nitrogen (N) and 0-4.6 tonnes/year for phosphorus (P). The highest annual N loss occurs in the case of a combination of agriculture or grassland with slow infiltration soils. In contrast, P loss is associated with agriculture or urban land use in combination with slow infiltration soils. By determining the sources and estimating the magnitude of nutrient pollution, nutrient mitigation solutions were considered for the peri-urban wetlands where low-income communities surround the immediate area and connections with urban and local communities facilitate options to conserve natural assets. In conclusion, controlling nutrient pollution can improve the protection of natural aquatic resources and the living conditions of local communities while generating other benefits for surrounding urban areas.