The Effects of Nitrogen on Biodiversity at Niwot Ridge
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| Graph of Precipitation Click for larger image |
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| Graph of Precipitation Click for larger image |
The prognosis is brighter on the agricultural front. Seastedt considers agriculture easier to fix than automobiles, because wasted nitrogen is wasted money to farmers. Slow-release fertilizers and improved sewage system which convert ammonium (agricultural nitrogen) to atmospheric nitrogen gas have been developed. Knowing the exact nitrogen needs of a crop helps by avoiding overfertilization, so the use of soil testing systems is on the rise. And livestock owners can now use reduced-protein feed, which results in less manure-borne methane and ammonium.
Though agriculture contributes a much smaller percentage of nitrogen pollution to Niwot Ridge than do automobile emissions, both are major contributors on Colorado's plains, where agriculture causes nitrogen to build up in soil and in rivers. For decades, excess fertilizer and livestock waste ran unchecked into groundwater. But with tighter regulations and increased awareness on the part of the agricultural community, that may be changing.
Some farmers, such as Dick Mercer, who runs Double M Farms in Kearney, Nebraska, have had success in reducing wasted nitrogen. Mercer manages 3000 acres of irrigated corn, and at any given time he oversees 3000 head of cattle. In 1996, his advanced composting techniques won him a National Cattleman's Beef Association's Environmental Stewardship Award.
He works with the city of Kearney to turn city sewage and his own farm manure into field fertilizer, and says it's just as effective as commercial forms. "Nitrogen is nitrogen," he says. And natural fertilizer goes one step better: it returns organic matter to the soil, up to 800 pounds per ton of fertilizer, whereas commercial fertilizer is composed only of nitrogen products, robbing soil of natural nutrients and upsetting the pH balance. In addition, Mercer monitors the nitrogen needs of his soil, so that less fertilizer is wasted. Nitrate levels in his watershed have steadily decreased over the years. "The pendulum has swung the other way," he says.
But agriculture as a whole has a long way to go, according to Mercer. Nebraska's Central Platte watershed has had nitrate levels above federal limits for at least 40 years, and Mercer doesn't expect the problem to be solved anytime soon. The expense and effort required to manage farmland wisely means that not everyone will be able to run their farms as he has. But Mercer feels the time will come when farming no longer harms its environment. "We've all become much more knowledgeable that the environment is fragile," he says. "I think most of us understand that we have an obligation."
Seastedt of INSTAAR feels that the government should address nitrogen pollution for economic reasons, if nothing else. Should nitrogen cause Colorado's weeds to flourish and fish to die sometime in the next decades, the government will find it much costlier to save what's left. Endangered-species preservation programs are much more expensive than maintaining stable biodiversity in the first place, he says. "It's the old ounce of prevention versus the pound of cure."
INSTAAR researcher Williams considers Niwot Ridge an early-warning system for nitrogen saturation in this country. Unlike more urban areas downslope, Niwot Ridge is not saturated yet, so monitoring the area is a good way to determine how much closer the ecosystem is to saturation and its consequences: acidified soil, poisoned waterways, and species driven to extinction. Pollution has "thrown a biological switch," he says, the consequences of which we can only begin to guess.
The good news about nitrogen pollution is that it spends less time in the soil than toxic wastes like radioactive sludge. And if pollution can be stopped, nature has the ability to reverse the effects of nitrogen saturation. "Most soils can restore themselves," Seastedt says, though it could take a millennia in the worst cases. Fortunately, stage 2 areas like Niwot Ridge can still turn back before damage is done. But until nitrogen pollution is reduced, the high tundra will remain threatened by the demands of a growing population.