Nitrogen Deposition as an Invisible Land-Use Change

Reactive nitrogen deposition (e.g., nitrate and ammonium delivered via wet and dry deposition) functions as a diffuse, large-scale fertilization experiment. While nitrogen can limit productivity in some systems, chronic deposition commonly pushes ecosystems beyond historical nutrient regimes, driving measurable changes in plant community composition, soil chemistry, and downstream water quality.

In nitrogen-sensitive habitats such as grasslands, heathlands, and some forest understories, added nitrogen often favors fast-growing, nitrophilous species that outcompete slow-growing specialists adapted to low-nutrient conditions. This can reduce plant diversity and alter habitat structure, with secondary effects on insects and higher trophic levels. In soils, nitrification and leaching can increase acidity, mobilize aluminum, and deplete base cations (calcium, magnesium), shifting microbial communities and changing decomposition dynamics.

Nitrogen deposition also propagates through watersheds. Elevated nitrate export contributes to eutrophication in lakes and estuaries, increasing the probability of harmful algal blooms and hypoxia. Because deposition sources include agriculture (ammonia volatilization), fossil fuel combustion (NOx), and industrial activities, mitigation requires cross-sector policies, not localized remediation.

Best-practice monitoring includes atmospheric deposition measurements, soil pH and cation status, vegetation composition, and aquatic nitrate concentrations. The key point is that nitrogen deposition behaves like land-use change: it redefines baseline conditions across regions, even in protected areas.