It is now a truism of environmental thinking that the great concern of water quality is no longer "point source" pollution, pollution arising at a point such as a factory, storm culvert, or municipal sewer facility. The great concern of water quality instead is "non-point source" pollution--seepage and runoff that has no single point on the land that we can point to and say, "See, the chemical is coming from here." One of the most ruinous chemicals of the American watershed is not some exotic, heavy metal; not some complexly mutated chemical like DDE as a breakdown product of DDT. It is, instead, a common, benign element: nitrogen. This element is essential to plant growth and it is present everywhere in the water system as well as in the atmosphere. Nitrogen is the major element in the air we breathe and this nitrogen is made available to the soil and plants through the electrical discharges of atmospheric lightning.
Nitrogen, however, is also present in the fertilizers we use and in the manure that is produced by every animal in our farm lots and yards. It was not without reason that on the working small farm I grew up on, the dried droppings of the chicken house were spread directly on the garden and plowed under. Chicken manure is an excellent fertilizer and is a rich source of nitrogen. In its place--near the root system--and in controlled amounts, nitrogen is essential to healthy plant growth and in agriculture to good crops. Excess nitrogen, however, quickly becomes out of place and finds its way into watersheds where it becomes a critical part of a complex process called eutrophication: a process where fertilizer is converted into aquatic plants which die and in the process of decay consume more oxygen than they produced as plants. The result of eutrophication is dead water: water too low in oxygen to support plants or animals.
A crisis case of environmental concern today is the Chesapeake Bay. Long known as the world's largest estuarial system and greatest natural harbor, the Chesapeake Bay is mostly dead. Here and there, oysters and blue crabs continue to be harvested, and here and there pockets of good water that are shielded from the larger circulation patterns of the bay are still highly productive. And here and there important recoveries have been made. But along the roads and the docks and wharves at the ends of them, a different story emerges--hundreds of shellfish businesses and still more hundreds of individual fishermen have gone out of business. Their crab sheds are closed and their boats are beached and rotting. The great shellfish and fish resources of the bay have disappeared, not merely from over fishing as population grew around Washington, D. C., but because the bay could not any longer support the rich aquatic life that once made it famous as the richest shellfish resource in the nation. The classic oyster/crab cuisine of Virginia and Maryland is now dependent upon shellfish imported from the Gulf Coast.
Point source pollution did not kill the Chesapeake Bay. Heavy industry did not kill the bay. Lawns and pig pens and pastures killed the bay. Nitrogen flows into the bay from every point in a watershed that reaches from New York to North Carolina. That nitrogen, along with other chemicals and the millions of tons of construction sediment that flows down the bay's great rivers, has killed the bay. Nitrogen pollution in the environment is very hard to control. The problem around the bay, reaching back along its tributary watersheds, is found in tens of millions of cars, in millions of lawns, in hundreds of thousands of Virginia and Maryland and Pennsylvania farms. This is pandemic non-point source pollution: a heavy dose of a killer element coming from everywhere. The changes in environmental usage necessary to restore the Chesapeake Bay must be comprehensive, detailed, long-term. Along the way, restoring the bay will challenge many of our cherished notions about American life: neat houses and lawns; well-kept farms.
For the lawns there is a very simple solution: abandon neatness and uniform green and never fertilize. To restore the bay, Virginia and Maryland may have to ban lawn fertilizer the way Los Angeles had to ban charcoal lighter fluid in order to deal with air pollution. With the farms, we come back to edges and fencerows. The old farms--the farms before weed eaters, bush hogs, and bull dozers--were healthier farms. Far fewer chemicals were used on those farms, and there was far less runoff from the pasture lot to the streams. A dense growth of weeds in the fencerow locks up nitrogen that other wise would enter the water system. We cannot imagine that we will tell the good Amish and Mennonite farmers of Pennsylvania, Virginia, and now Tennessee that they should not be so successful in raising cows--but we can imagine in Tennessee as well as around the Chesapeake Bay that our waters would be healthier if our farms were not so neat.
Tennessee faces a similar problem. But unlike the Chesapeake Bay which is picturesque and located in an area of high profile environmental thinking, the problem in Tennessee cannot be pointed to in so dramatic a fashion. In fact, things in Tennessee look pretty good. Our farms are productive, our lakes and rivers support fish, and no famous resource is so endangered as to engender alarm. Yet, in some years in the last decade Tennessee has been at the top of the list of states in pollution of its waters due to siltation. And in Tennessee as around the Chesapeake Bay, the fundamental concern of conservationists and environmentalists is with non-point source pollution of Tennessee waters. Point source pollution is typically industrial and municipal. Non-point source pollution is typically domestic and agricultural. In Tennessee, farms, woodlots, and lawns are the same kind of problem that they are in Pennsylvania.
The siltation discoloring Tennessee's rivers and filling up our lake reservoirs decades ahead of their planned obsolesence is a matter of both silt and fertilizer. Silt chokes and covers and smothers, but the process that washes silt from the land into the waters is the same process that carries the excess fertilizer into the waterways. The Chesapeake Bay has complicated flow, eddy, and back flow patterns that make water circulation difficult to model, but which, together, keep the problem of eutrophication focused in an observable area. The flow-through--flush--characteristic of the Tennessee river and lake system means that many of our problems are not actually seen at all and may not be felt until our silt and fertilizer becomes part of the growing delta of the Mississippi River below New Orleans.
Locally, however, the problems are serious if not critical. Many of our lakes remain discolored for months. Some of the discoloration is from the wave action of the tens of thousands of power boats eroding shoreline around the lakes. A significant portion of the discoloration derives from siltation--runoff from our farms where improperly kept fields wash away into ditches--into the second stream system of the roads--and then into our rivers and lakes. As the technology and the aesthetic of neatness has beguiled us, we have cleared and bull dozed hundreds upon hundreds of miles of the edge filters that once protected the rivers. We have cleared lanes and fencerows and we have plowed fields right to the very edge, not of right-of-way, but the edge of the road itself. And near our houses and sometimes all along our corn and wheat crops, we mow the low edge weeds that might have kept the soil in the field instead of in the ditch.
An Edge Water Quality Sampler
A calculation: How Much Does a Row of Corn Cost?