Based on our review of available scientific evidence, we are certain that human alterations of the nitrogen cycle have:

1) approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing;

2) increased concentrations of the potent greenhouse gas N2O globally, and increased concentrations of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth;

3) caused losses of soil nutrients, such as calcium and potassium, that are essential for the long-term maintenance of soil fertility;

4) contributed substantially to the acidification of soils, streams, and lakes in several regions; and

5) greatly increased the transfer of nitrogen through rivers to estuaries and coastal oceans. In addition, based on our review of available scientific evidence we are confident that human alterations of the nitrogen cycle have:

6) increased the quantity of organic carbon stored within terrestrial ecosystems;

7) accelerated losses of biological diversity, especially losses of plants adapted to efficient use of nitrogen, and losses of the animals and microorganisms that depend on them; and

8) caused changes in the composition and functioning of estuarine and nearshore ecosystems, and contributed to long-term declines in coastal marine fisheries.