Each year in the United States, 11 million tons of NPK chemical fertilizers are spread on lawns for the sake of aesthetics. But that bright green lawn has consequences. More and more, scientists are asking if those beautiful lawns are worth the pollution of our precious waterways (especially when organic turfcare methods are cost-effective and successful). Dead zones are being formed in bodies of water around the country with disastrous consequences.
A “dead zone” is an area of water so low in oxygen that it cannot support aquatic or marine life. We call this lack of oxygen “hypoxic.” Dead zones are caused by an excess of nitrogen and phosphorus in the water. The ‘N’ and ‘P’ of NPK chemical fertilizers refer to nitrogen and phosphorus. Runoff from rain and irrigation wash these nutrients into our waterways.
When the excess phosphorus and nitrogen reach our water systems, they trigger a bloom of phytoplankton and zooplankton. As these plankton die, they sink below an area of water and begin their natural process of photosynthesis. But this natural process, done at such an unnatural level, exhausts the water’s oxygen which is fatal to much of the aquatic and marine life in that area.
An example of this decimated aquatic life? The oyster.
Oysters work around the clock as nature’s water purification system. They keep bodies of water like Chesapeake Bay clean and clear by filtering the water through their gills to rid it of excess nutrients. But Chesapeake Bay’s oyster population has been declining rapidly–due to a dead zone in the water–down to only 3% of what it should be. When oyster levels are correct, Chesapeake Bay is completely filtered in a matter of days. Now, with the shrunken oyster population, it may take well over a year.
One of the newest and most notorious dead zones is the 20,000 square kilometer region in the Gulf of Mexico where the Mississippi River dumps runoff from its drainage basin. Much of this runoff comes from big-business agriculture in the Midwest. But much of it also comes from individual homeowners using chemical fertilizers on their lawns.
Dead zones can be reversed, but only if the industrialized world changes its habits. The Black Sea dead zone used to be the largest in the world but more or less disappeared between 1991 and 2001 when chemical fertilizers became too expensive after the collapse of the Soviet Union. The improved conditions occurred largely by accident, but this example speaks volumes. Fertilizers are destroying the world’s seas, and only by ceasing the use of synthetic chemical fertilizer can they be improved.
If the trend of the past 50 years continues, it will no longer be certain that it is safe to swim in the Chesapeake Bay or eat the fish harvested from it. The dead zones, predominantly caused by nitrogen poisoning, will take over, leaving the entire bay essentially dead. Even projects such as stocking creek beds with oysters to recreate the oyster population will be fruitless. Unless we reduce our dependence on synthetic chemical fertilizers, dead zones will continue to appear not only in the Chesapeake Bay, but in many other important waterways.