Human activities now contribute as much to the global supply of fixed nitrogen each year as natural processes do. And through biomass burning and land clearing we mobilize an additional amount of nitrogen equal to half of the natural production. This overall human contribution could double over next 25 years. Natural systems can absorb some of this excess and even flourish, but after that serious harm can ensue. This nitrogen glut can disrupt soil chemistry and reduce fertility and change the composition of species in an ecosystem.
Aquatic ecosystems are the most at risk.
Dead zones, such as that in the Gulf of Mexico, are a direct result of overfertilization of the waters, largely from agricultural runoff. We know a great deal about policy changes that could dramatically improve many of the worrisome trends noted above. Many of the pressures on renewable resources are exacerbated by the presence of public subsidies that promote overharvesting or overuse of resources. Paying the full costs of goods and services. Many of the environmental impacts of our production and consumption are externalized .