Sir

Your News Feature “Fertilized to death” (Nature 425, 894–895; 2003) deals with an extremely important issue: reactive nitrogen and the need to increase the efficiency of nitrogen fertilizers. James Galloway's work, as well as that of the IVL Swedish Environmental Research Institute, has pointed to significant environmental problems with excess reactive nitrogen.

Although environmental concerns about excess nitrogen are worth highlighting, the need to produce more food, more efficiently, in many parts of the world is even more urgent. Energy expert Vaclav Smil estimates that approximately 40% of the world's dietary protein supply in the mid-1990s originated from fertilizer nitrogen (V. Smil Enriching the Earth 156–161, MIT Press; 2001). Agronomists and soil scientists throughout the world are working to make nitrogen use in farming more efficient for both food production and environmental reasons.

Although cutting back on fertilizer use might be a method to reduce the total load of reactive nitrogen in developed countries with excess food production capacity, it is not an acceptable solution in countries with malnourished people. The effect of increased food costs on people with low incomes in developed countries must also be considered. Efficiency improvements can help reduce nitrogen-fertilizer consumption if populations stabilize, and reduce its impact on the environment.

Ecologists, agronomists, environmental groups and industry must join to increase nitrogen-fertilizer efficiency for the benefit of everyone. Publications such as Nature should lead the way in building inter-disciplinary support for this worthy goal.