Robert Howarth
"From Mountain to Sea: Nutrient Cycles Out of Balance"
Wednesday, May 01, 2002, 12:30 PM
Dr. Robert Howarth - Cornell University
Nitrogen generated by localized activities, from agricultural fertilizers to car exhaust, is polluting global ecosystems and threatening the life cycles they support. Dr. Robert Howarth tracks the fate of nutrients from land to ocean, and attempts both to address fundamental ecological questions and to contribute to practical issues of environmental management. Dr. Howarth is the David R. Atkinson Professor of Environmental Biology at Cornell University and directs the Oceans Program for Environmental Defense. Among many positions, Howarth is a fellow of the Aldo Leopold Leadership Program.
Howarth's research interests have included how wetlands interact with coastal waters, the ecological effects of oil spills, nutrient pollution and nutrient cycles in both lakes and coastal marine ecosystems, and human alteration of biogeochemical cycles (nitrogen, phosphorous and sulfur) at regional to global scales. He has edited 6 books and published over 120 research papers.
Howarth and his family own a small farm in Trumansburg, NY.
LECTURE SUMMARY
Dr. Robert Howarth, combines the intellectual rigor of a research scientist, the leadership skills to keep several dozen colleagues focused on an acute but under-appreciated environmental issue, and the personal touch to work with both sides of congress to help incorporate sustainability measures into agriculture legislation.
He spoke about a problem no less important than global climate change, biodiversity loss, world hunger, or human health…actually a problem that profoundly affects all four of the above: human overloading of nutrient cycles, especially nitrogen.
OK, nitrogen isn’t sexy. Public awareness of the problem may be where climate change and biodiversity were twenty years ago. And the problem has grown so rapidly that we may not have 20 years to get the public and policy-makers up to speed. Half of all nitrogen used in the history of the United States was used in the last fifteen years. Looking at the big picture, natural nitrogen production on land amounts to about 95 teregrams (which is approximately…well, a lot). Human production is 155 teragrams (in technical terms, way more than a lot).
The main sources of human-generated nitrogen production are agricultural fertilization and fossil fuel burning. The results are several:
• Wholesale changes in food webs and biodiversity in soils, rivers, and coastal areas.
• Nitrogen dead zones worldwide (one the size of New Jersey at the Mississippi delta).
• Ozone creation at ground level.
• Particulate haze with severe health effects (e.g., cancer).
• Acid rain and acidification of lakes.
• Ozone holes in the stratosphere.
• Greenhouse gas production.
This is not a simple problem. Nitrogen production is patchy, region by region, and it has its benefits. In the near term, nitrogen fertilization alleviates hunger. But in the long term the over-production of food in the world allows population to grow beyond carrying capacity, risking more catastrophic famines. The artificial production of fertilizer fueled the ‘green revolution’ and developing countries are some of the biggest users of fertilizers – China uses over 1/3 of the world’s fertilizer.
One of the big drivers of over-fertilization and nitrogen air pollution is a recently transformed agriculture industry. We now feed our animals a corn diet, rather than grasses – as we had until about 1970. Corn is a fertilizer hog. It is leaky. Its small root system doesn’t hang onto nutrients, so they tend to wash away. And now that livestock is raised in feedlots separate from crops, we are left with a waste product that is flushed - or blown - away rather than recycled to crops. Add to all this the fact that farmers tend to over-fertilize by an average of 30% even in the face of convincing evidence that this is a money-losing practice.
On the fossil fuel emissions side, the good news is that nitrogen oxide gases have stabilized under the Clean Air Act. The bad news is that the other targeted gases have decreased. For example, sulfur dioxide – the main culprit in acid rain – is decreasing, and nitrogen oxides will be taking over as the main cause of acid rain.
Sounds pretty daunting, and if we keep on this trajectory, the nnitrogen-overload problem will get a lot worse. But there are a few straightforward steps we can take to turn this situation around. Farmers can:
• Move from corn/soybeans to a grass system, reducing fertilizer use 30-to-50-fold.
• Employ winter cover crops to restore and hold soil.
• Fertilize in the spring when plants can take up fertilizer, rather than in the fall.
But farmers have been reluctant to do these things, even in the face of overwhelming evidence of the benefits (reduce fertilizer by 30% and yield remains the same; reduce it by 50% and yield decreases by only 5%). Dr. Howarth suggested several policy changes that could help farmers move toward a more sustainable agriculture. His lead idea: we’re stuck with farm subsidies for the foreseeable future, so why not subsidize farmers to reduce fertilizer use and move to a grass system, cover crops, and spring fertilization?
And in light of the fact that animal feedlots are driving much of this problem (the pig feedlots in North Carolina alone produce more nitrogen waste than New York City and New England combined) … eat less meat. And for us Pleistocene hunter-gatherer types, eat free-range grass-fed meat.
