Livestock Sector Drives Increasing Water Pollution

By Lisa Raffensperger
World Resources Institute; Earth Trends Environmental Information; January 30, 2008

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Anyone who’s ever seen a cow pasture would likely recognize some of the most immediate environmental impacts of large-scale livestock farming–trampled ground, eroded stream banks, lots of manure. However, a less visible but equally worrisome effect appears thousands of miles from the Midwest’s muddy cow pastures, in the tropical waters of the Gulf of Mexico. Amidst increasing concern for the growing ‘dead zone’ where the Mississippi River flows into the Gulf, livestock farming practices are increasingly coming under scrutiny. In fact, the FAO says, the livestock sector is the major driver of increasing water pollution in most geographical areas.


The Mississippi‘s Loaded Waters

The Mississippi River drains 41 percent of the contiguous United States into the Gulf, a drainage basin that includes almost all the country’s industrial livestock farms and livestock feed production. Rainwater runoff, treated sewage, and other wastewater add to the river’s nutrient load. When dumped into the Gulf, these nutrients are consumed in explosive algal blooms, driven largely by nitrogen and phosphorous. When the blooms die and sink to the bottom, they are decomposed by bacteria on the ocean floor. In the process, these bacteria drain the water of its dissolved oxygen, forcing fish, shrimp, and other marine life to relocate to survive. The dead zone in the Gulf of Mexico is the second biggest in the world, comprising thousands of square miles where the dissolved oxygen is so low that the water can support only the most minimal life. 

Industrial-scale farms in the U.S. produce over 335 million tons of manure per year, directly contributing over 3 million tons of nitrogen to the Mississippi River in the year 2000. This is less than half the amount of nitrogen the USGS estimated that fertilizer contributed in the same year. A direct comparison would seem to indicate that crop farming is of far bigger concern than livestock.

However, a direct comparison obscures just how much of this fertilizer is involved in livestock production. According to the FAO, one-third of total arable land worldwide is dedicated to feedcrop production to support livestock. This means that a substantial portion of fertilizers applied to farmland are in actuality supporting livestock production. In the U.S., the production of livestock and their feedcrops is responsible for one-third of the nitrogen and phosphorous discharged into freshwater.


A Global Problem

According to the FAO, global statistics on water pollution by livestock are not available. But the problem is not a localized one, as the U.S. accounts for only 7 percent of the world’s cattle stocks. Arguably few other countries have the kind of concentrated industrial cattle farms that the U.S. has, which intensify the runoff problem. However, with Asia’s meat production rising faster than any other region over the last 10 years and focused largely in China, densely-populated developing countries will doubtlessly follow the U.S. in minimizing land use by instituting factory farming.

The Gulf of Mexico may just be a glimpse into the future of coastal waters around the world, if this is the case. Already, dead zones have been identified across the globe, from the Scandinavian fjords to the South China Sea to the U.S.’s Chesapeake Bay. The demand for meat has doubled in the last 30 years and is still rising, driven largely by lower- and middle-income individuals in rapidly developing countries like Brazil, China, and India. Without better livestock farming practices, or a significant change in eating habits, our dietary preferences will drive expanding dead zones around the world.

New York Times Jan. 27 article, "Rethinking the Meat-Guzzler"