Publicações

Increased N deposition has been identified as a current global change concern for biodiversity and human health, and excess reactive nitrogen due to human activity has had numerous effects on terrestrial and aquatic ecosystems in the Northern Hemisphere. However, very little is known about the magnitude of deposition or its impacts in ecosystems outside of North America and Europe. There are a number of reasons for this discrepancy, centered on: the lack of monitoring and long-term measurements of both wet and dry N deposition; the range of tropical and aridland ecosystems with very different potential responses to increased N deposition and that are currently without substantial impact; the prevalence of fire as a driver of nutrient cycles in savannas and grasslands; and the intense concentration of human activity in vast urban areas. Currently, compared to other human impacts such as land-use change (i.e. deforestation), agricultural expansion and intensification, urbanization and climate change, N deposition effects are relatively localized and at present, largely unrealized. In addition, many areas outside of North America and Europe suffer from substantial nitrogen deficits, which highlight the necessity for establishing appropriate region-specific research priorities. While a solid understanding of the potential impacts on N deposition in Southern Hemisphere ecosystems in the next century is important, it may be most prudent to focus on mitigation that improves agricultural nitrogen use efficiency and conservation of natural ecosystems rather than critical loads, with policies that demonstrate corollary benefits to reduce excess nitrogen input in Southern Hemisphere aquatic and terrestrial ecosystems.