Nitrogen: Too much of a vital resource
d. Vries, W.
Nitrogen (N) is a key nutrient, vital for the survival of humans and all other living organisms. While di-nitrogen gas (N2) is abundant in the atmosphere, most organisms are unable to use this chemically unreactive form. First it must be converted or fixed߿ݠinto a reactive form such as ammonia (NH3) or nitrogen oxide (NOx). These and other forms of reactive nitrogen (Nr) are comparatively scarce and represent a limiting resource in most natural ecosystems and in farmlands. In fact, the composition of much of the worlds terrestrial biodiversity is the result of limitations in the availability of reactive nitrogen. By the turn of the 19th century, the natural sources of fixed nitrogen were not sufficient for the food production needs of a rapidly increasing human population in Western Europe. The development and adoption of a process to produce and use synthetic N fertilizers, led to a dramatic increase in agricultural productivity. However, because of the generally low efficiency in nitrogen fertilizer use in agriculture, much of industrially fixed nitrogen is released into the biosphere. The burning of fossil fuels also releases large amounts of reactive nitrogen oxide emissions into the atmosphere. Because of these releases, and the fact that we convert more nitrogen from the atmosphere into reactive forms than all of the Earths natural processes in terrestrial systems combined, we have now dramatically altered the global nitrogen cycle-even more than we have altered the global carbon cycle.
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