Investigating the Effects of Agricultural Practices on Freshwater Ecosystem Health and Biodiversity

Abstract

Intensive row-crop agriculture practices remain one of the principal causes of landscape change. Intensive cultivation practices affect both the health and biological diversity of nearby freshwater networks. The impacts of agrochemical loading and withdrawal of stream water for irrigation, as well as those resulting from intense agricultural tiling, were evaluated as systemic stresses on macroinvertebrate communities in river ecosystems. Two decades of integrated data on stream ecosystems and macroinvertebrates are used to identify the ecologically relevant pathways (eutrophication from enrichment; pesticide assimilation; siltation from physically degraded habitats) by which intensively managed agricultural landscapes impact downstream ecosystems. Evidence indicates that stream reaches immediately downstream from row-crop agricultural lands have decreased EPT taxonomic richness (58% loss relative to less intensely managed lands) and a subsequent decrease in functional feeding group diversity, which represents a degradation of macroinvertebrate community structure. Chronic exposure to low-dose mixtures of pesticides alters macroinvertebrate communities by diminishing overall processing capacity within the ecosystem, diminishing leaf-litter processing rate, and altering the efficiency of energy transfer between trophic levels. Effective, preventive conservation alternatives were evaluated and included integrated pest management, variable-rate fertilizer application, and the establishment of unbroken stream-riparian buffer corridors. Integration of catchment land-use management practices, including variable-rate fertilization, along with targeted nutrient loading objectives, promotes ecosystem resilience, enhances biodiversity, and maintains ecosystem services. These findings highlight the critical role of management efforts at a catchment scale in freshwater conservation, emphasizing the significance of sustainable agriculture to balance production and ecosystem function. A quantitative decision-making tool for conservation is presented that relies on the demonstration that science-based, integrative land-use management is necessary for restoring and maintaining sustainable freshwater systems and the bio complexes they harbor.