Nitrogen fertilisers cause biodiversity loss – study

Posted by Laura Grant on March 1, 2008
Posted in Conservation

wheat field © iStockphoto.comNitrogen-rich fertilisers have been shown to reduce biodiversity even in areas where they are applied in low amounts, the US National Academies reports. A recent study, published in Nature, looked at the biodiversity of agricultural plots subjected to slow fertilisation with nitrogen and others that were left alone as a control over a 20 year period. The fertilised plots showed a 17 percent drop in plant species compared to the control plots. The plots where nitrogen fertilisation was stopped in the middle of the study showed significant signs of recovery, though. This suggests that much of the damage can be undone.

An ecological consequence of excess nitrogen in the Mississippi River, from soil erosion and runoff from agricultural, is the creation of a dead zone in the Gulf of Mexico – an oxygen-depleted area where most forms of marine life cannot survive. The dead zone is caused by a seasonal surge in the growth of algae, stimulated by nutrients such as nitrogen and phosphorus flowing into the gulf from the Mississippi and Atchafalaya rivers. The algae sinks and decays in the bottom waters. The decaying algae consume oxygen faster than it can be replenished from the surface and this reduces the amount of oxygen in the water, writes the NOAA. In 2006, the dead zone measured 6,600 square miles.

Source: The National Academies

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