Nitrogen emissions along the Colorado front range: Response to population growth, land and water use change, and agriculture

while N emissions are not commonly linked to land use change, the production of fixed nitrogen is strongly related to activities associated with urbanization, such as construction, production of energy, and development and use of transportation corridors. Agricultural intensification, brought about by application of synthetic N fertilizers and industrial-scale animal feeding operations, is another land use change that increases N emissions. The Colorado Front Range region experienced rapid population growth from 1980 (1.9 million) to 2000 (2.9 million). Emissions from point (power plants and industry) and mobile (highway and off road vehicles) sources were responsible for most of the increase in emissions since 1980. Agriculture (cropped and grazed land and livestock) was the other important source of N emissions. Soil emissions from cropped and grazed lands remained stable while livestock emissions increased slightly due to more cattle and hogs in feedlots. Although cause and effect relationships between increased N emissions and eutrophication of particular ecosystems are difficult to establish, higher N deposition has been observed at alpine sites near the headwaters of the South Platte River commensurate with the rise in emissions. The ecosystem responses of alpine systems to N deposition are likely to be the result, albeit an indirect one, of land use change.