Corn’s ecological footprint

High-yield corn agriculture in America provides obvious benefits, but a new study shows it’s also correlated with environmental problems – some of which can be detected by fishers thousands of miles away.  While using the words corn and nitrogen in the same sentence may sound as boring as a discussion of tractor tires, the issue is actually one of the most important environmental issues around.

High-yield corn production requires fertilizer to provide nutrients for the plants.  As reported in the journal Frontiers in Ecology and the Environment, this practice is also linked with higher nitrogen in nearby rivers: much of the nitrogen fertilizer washes away from the fields and winds up in streams that feed larger rivers.  Broadly speaking, this creates two major problems.

First, the excess nitrogen in the water fuels “dead zones” in rivers and in oceans.  Just as the nitrogen helps corn grow in fields, it also helps algae grow in water.  But because algae has a much more rapid life cycle – it grows and dies quickly – algal blooms create masses of decaying algae in a short period of time.  As algae decompose, oxygen is rapidly depleted, and fish and shellfish are unable to survive in these areas.  

Secondly, though we need nitrogen, we need a delicate balance of it to sustainably enjoy crops and fish.  Excessive nitrogen can be as problematic as scarce nitrogen.  This issue has received less attention than global warming and carbon footprints, but scientists are increasingly concerned about the impacts of using nitrogen unwisely.

The new study showed a strong correlation between intensive corn production and nitrogen in rivers, indicating this type of agriculture is associated with the two problems described above.  But where more types of crops were grown, the levels of nitrogen in rivers decreased.  

The study authors suggest their findings should play a role in determining agricultural policies to curb nitrogen runoff. Some existing practices which can help reduce runoff include increasing buffers between cropland and surface water, changing in crop rotation, and using native plants in some parts of fields to help keep the nitrogen from leaving the fields.

The article is free to read on the journal’s website.