Severe algal growth blocks light that is needed for plants, such as seagrasses, to grow. When the algae and seagrass die, they decay. In the process of decay, the oxygen in the water is used up and this leads to low levels of dissolved oxygen in the water. This, in turn, can kill fish, crabs, oysters, and other aquatic animals.
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Nutrients come from a variety of different sources. They can occur naturally as a result of weathering of rocks and soil in the watershed and they can also come from the ocean due to mixing of water currents. Scientists are most interested in the nutrients that are related to people living in the coastal zone because human-related inputs are much greater than natural inputs.
Because there are increasingly more people living in coastal areas, there are more nutrients entering our coastal waters from wastewater treatment facilities, runoff from land in urban areas during rains, and from farming.
Agriculture—including how we grow, raise, transport, process, and even store food and nonfood crops and agriculture products—has a profound effect on the planet. Think of what it takes to feed, for example, the almost 9.5 billion animals raised for food each year in the United States. Or what goes into growing this country’s more than 90 million acres of corn, used mainly for livestock feed and ethanol production. The monumental quantities of fertilizers and pesticides that go into those operations (and all the manure that comes out) are just a few examples of the pollution associated with agriculture. Here’s your guide to making sense of the many and varied impacts of our farming practices.
Agricultural pollution is the contamination we release into the environment as a by-product of growing and raising livestock, food crops, animal feed, and biofuel crops.
