By Jennifer Molnar

To solve a problem caused by seemingly unrelated actions — such as marine pollution — we need to understand what the connections are.
 
We are beginning to see the links between the causes and impacts of global warming. People are using more efficient light bulbs and/or driving smaller cars to protect polar bears thousands of miles away. 
 
Reducing marine pollution — especially nutrient pollution — also requires that these connections be made. How else can we address the fact that excess fertilizer applied to a corn field in Iowa contributes to the dead zone in the Gulf of Mexico, over 1,000 miles downstream?

Too Many Nutrients is a Bad Thing

Nutrients are essential to all organisms, but they are usually in limited supply in nature.

Humans, however, release vast amounts of nutrients to the environment — especially in fertilizers applied to crops and in livestock manure.

And these nutrients flow into rivers and ultimately to the ocean. For instance, we have increased by 6-fold the amount of nitrogen — a key nutrient — that is funneled toward the world’s coasts.

The consequences of this pollution are dire, because too many nutrients in coastal waters can disrupt marine ecosystems:

• Coral reefs can be overgrown by algae that would not grow in naturally nutrient-limited tropical waters. 
   
• Nutrient pollution can feed blooms of floating toxic algae that can kill fish and marine mammals and sicken people who eat shellfish. 
   
• In the most extreme cases, dead zones form when algae in coastal waters are overfertilized and bloom. When the algae die and decay, most if not all of the oxygen in the water is consumed, making the habitat unlivable for fish and other marine life.

Attacking the Problem at the Source

To reduce the impacts of nutrient pollution in marine ecosystems, we need to go to the source. This is where that farm in Iowa comes in — along with innumerable other farms.

Nutrients released in watersheds covering 40 percent of the United States and part of Canada are funneled through the Mississippi River into the Gulf of Mexico — where they cause a dead zone the size of New Jersey.

Getting rid of that dead zone — or reducing the impacts of nutrient pollution in other coastal waters — requires actions upstream in the watershed.
 
We can make a difference by making informed decisions on how we grow our food — whether crops or livestock — as well as biofuels. These decisions can include using only as much fertilizer as crops need, and encouraging the cultivation of crops that require less fertilizer.

Another Solution — Keep Habitats Intact

Conserving lands strategically can reduce the amount of nutrients carried downstream as well. Protecting natural habitats from conversion to urban areas or agriculture can reduce the amount of nutrients released into the environment. 

Intact habitats can also act as buffers, with vegetated barriers along shorelines helping to absorb nutrients before they reach rivers.

A recent study by a Nature Conservancy partner (.pdf) showed that lands conserved in the Wood-Pawcatuck River Basin in Rhode Island contributed significantly to preventing nitrogen inputs to the coast. Conservancy conservation planners are developing methods to incorporate this “upstream” thinking into marine conservation.
 
Wouldn’t it be great if a forest is conserved in order to protect fish swimming in the ocean thousands of miles away? It's within our reach — if we make the connection.  

Nature picture credits (left to right): © Mark Godfrey (Mississippi River); Courtesy Jennifer Molnar (Jennifer Molnar)