(I received the report summarized below as a sort of New Year's gift
from Jerry Brunetti who was forwarding it from Gary Wegner of
Natural Aeration Inc. Nutrient Cycling Advisory Team
<http://www.CIRCUL8.com>www.CIRCUL8.com. The original source appears
to be The Ecological Society of America. Contact me through personal
mail if you'd like the entire 60k report emailed to you. Happy New
Year! -Allan)
Human Alteration of the Global Nitrogen Cycle
Causes and Consequences
By Peter M. Vitousek, Chair, John Aber, Robert W. Howarth, Gene
E. Likens, Pamela A. Matson,
David W. Schindler, William H. Schlesinger, and G. David Tilman
SUMMARY
Human activities are greatly increasing the amount of nitrogen
cycling between the living world and the soil, water, and atmosphere.
In fact, humans have already doubled the rate of nitrogen entering
the land-based nitrogen cycle, and that rate is continuing to climb.
This human-driven global change is having serious impacts on
ecosystems around the world because nitrogen is essential to living
organisms and its availability plays a crucial role in the
organization and functioning of the world's ecosystems. In many
ecosystems on land and sea, the supply of nitrogen is a key factor
controlling the nature and diversity of plant life, the population
dynamics of both grazing animals and their predators, and vital
ecological processes such as plant productivity and the cycling of
carbon and soil minerals. This is true not only in wild or unmanaged
systems but in most croplands and forestry plantations as well.
Excessive nitrogen additions can pollute ecosystems and alter both
their ecological functioning and the living communities they support.
Most of the human activities responsible for the increase in global
nitrogen are local in scale, from the production and use of nitrogen
fertilizers to the burning of fossil fuels in automobiles, power
generation plants, and industries. However, human activities have not
only increased the supply but enhanced the global movement of various
forms of nitrogen through air and water. Because of this increased
mobility, excess nitrogen from human activities has serious and
long-term environmental consequences for large regions of the Earth.
The impacts of human domination of the nitrogen cycle that we have
identified with certainty include:
* Increased global concentrations of nitrous oxide (N2O), a
potent greenhouse gas, in the atmosphere as well as increased
regional concentrations of other oxides of nitrogen (including nitric
oxide, NO) that drive the formation of photochemical smog;
* Losses of soil nutrients such as calcium and potassium that
are essential for long-term soil fertility;
* Substantial acidification of soils and of the waters of
streams and lakes in several regions;
* Greatly increased transport of nitrogen by rivers into
estuaries and coastal waters where it is a major pollutant.
We are also confident that human alterations of the nitrogen cycle have:
* Accelerated losses of biological diversity, especially among
plants adapted to low-nitrogen soils, and subsequently, the animals
and microbes that depend on these plants;
* Caused changes in the plant and animal life and ecological
processes of estuarine and nearshore ecosystems, and contributed to
long-term declines in coastal marine fisheries.
National and international policies should attempt to reduce these
impacts through the development and widespread dissemination of more
efficient fossil fuel combustion technologies and farm management
practices that reduce the burgeoning demand for and release of
nitrogenous fertilizers.
FURTHER "SUMMATION" by Gary Wegner
Summary of
Human Alteration of the Global Nitrogen Cycle Causes and Consequences
Page 1 paragraph 3
The impacts of human domination of the nitrogen cycle that we have
identified with certainty include:
Increased global concentrations of nitrous oxide (N2O), a potent
greenhouse gas, in the atmosphere
Greatly increased transport of nitrogen by rivers into estuaries and
coastal waters where it is a major pollutant.
Page 2 paragraph 6
Quantifying the rate of natural nitrogen fixation prior to human
alterations of the cycle is difficult but necessary for evaluating
the impacts of human-driven changes to the global cycling of
nitrogen. The standard unit of measurement for analyzing the global
nitrogen cycle is the teragram (abbreviated Tg), which is equal to a
million metric tons of nitrogen.
Page 2 paragraph 9
The process of manufacturing fertilizer by industrial nitrogen
fixation was first developed in Germany during World War I, and
fertilizer production has grown exponentially since the 1940s. In
recent years, the increasing pace of production and use has been
truly phenomenal. The amount of industrially fixed nitrogen applied
to crops during the decade from 1980 to 1990 more than equaled all
industrial fertilizer applied previously in human history.
Page 3 paragraph 5
Human Versus Natural Nitrogen Fixation
From this evidence, it is fair to conclude that human activities have
at least doubled the transfer of nitrogen from the atmosphere into
the land-based biological nitrogen cycle.
Page 4 paragraph 4
The concentration of nitrous oxide in the atmosphere is currently
increasing at the rate of two- to three-tenths of a percent per year.
Page 4 paragraph 10
Nearly 70 percent of global ammonia emissions are human-caused.
Ammonia volatilized from fertilized fields contributes an estimated
10 Tg per year; ammonia released from domestic animal wastes about 32
Tg; and forest burning some 5 Tg.
Page 7 paragraph 3
High levels of nitrates in drinking water raise significant human
health concerns, especially for infants. Microbes in an infant's
stomach may convert high levels of nitrate to nitrite. When nitrite
is absorbed into the bloodstream, it converts oxygen-carrying
hemoglobin into an ineffective form called methemoglobin. Elevated
methemoglobin levels - an anemic condition known as methemoglobinemia
- can cause brain damage or death. The condition is rare in the U.S.,
but the potential exists whenever nitrate levels exceed U.S. Public
Health Service standards (10 milligrams per liter).
Page 9 paragraph 3
One way to reduce the amount of fertilizer used is to increase its
efficiency. Often at least half of the fertilizer applied to fields
is lost to the air or water. This leakage represents an expensive
waste to the farmer as well as a significant driver of environmental
change.
