Nitrogen can act as a fertilizer causing some plants to grow faster and out-compete others. This effect can be useful for lawns and crops, but is undesirable in national parks where natural vegetation and healthy soils and waters are important in protecting the parks for future generations. Research in the park shows that nitrogen deposition has caused changes in high-elevation water chemistry, soil chemistry, tree chemistry, and algal communities on the east side of the park. These changes impact park ecosystem health and are sufficient to meet the "harmful effect" definition for exceedence of nitrogen deposition critical loads. The Superintendent of Rocky Mountain National Park has identified 1.5 kg/ha/yr wet deposition as the critical load for nitrogen fertilization, and as a park resource management goal based on specific, published research showing that wet deposition levels at the time the biological changes started to occur (1950-1964) was around 1.5 kg/ha/yr.
