What is the most significant environmental consequence of increased nitrogen deposition in terrestrial ecosystems?

The most significant environmental consequence of increased nitrogen deposition in terrestrial ecosystems is the disruption of nutrient balances, leading to shifts in plant community composition and loss of biodiversity. Nitrogen deposition refers to the input of reactive nitrogen compounds from the atmosphere to the earth's surface. These compounds can originate from various sources, including agricultural fertilizers, industrial emissions, and vehicle exhaust. While nitrogen is an essential nutrient for plant growth, increased nitrogen deposition can have detrimental effects on ecosystems. In many terrestrial ecosystems, nitrogen is a limiting nutrient, meaning that plant growth is primarily limited by the availability of nitrogen. When nitrogen deposition increases, it can lead to excessive plant growth, particularly of nitrogen-loving species. This can outcompete native species that are adapted to low-nitrogen conditions, leading to a decline in their populations. The shift in plant community composition can alter ecosystem structure and function, affecting nutrient cycling, water availability, and wildlife habitat. Increased nitrogen deposition can also lead to soil acidification, as nitrogen compounds are converted to nitric acid in the soil. Soil acidification can harm soil organisms and reduce the availability of other essential nutrients, such as phosphorus and calcium. Furthermore, increased nitrogen deposition can contribute to the eutrophication of aquatic ecosystems, as excess nitrogen is leached from terrestrial ecosystems into rivers and lakes. This can lead to algal blooms, oxygen depletion, and fish kills. The long-term consequences of increased nitrogen deposition can include loss of biodiversity, altered ecosystem function, and reduced ecosystem resilience to other environmental stressors.