The purpose of this letter is to comment specifically on the three options for the long-term Coastal Goals.
Hypoxia in the Northern GOM is largely driven by non-controllable factors,i.e., weather conditions in both the GOM and in the MR drainage basin. Turbulent weather during the summer in the GOM greatly reduces the extensiveness and intensity of hypoxia compared to those summers with calm,stagnate weather patterns. In addition, above-normal spring precipitation in the heart of the Cornbelt, where most of the nitrates are being lost, will deliver a much greater load of nitrate to the GOM than a year in which dry conditions prevail in the spring. This is especially true when a wet spring follows a wet year(s). Above-normal precipitation in mid- to late summer is likely to deliver much lower loads of nitrate than the same amount of precipitation in February - May, These climatic effects and how they impact nitrate loading are discussed in the CENR Topic 5 Report.
Therefore, I find it almost impossible to establish quantitative goals such as A & B and expect them to be satisfactory yardsticks for measuring progress toward reducing the hypoxic zone. The size of the hypoxic zone the last two years is a perfect example of the difficulty associated with these two quantitative goals. In 1999, the hypoxic zone was the largest in modern-day records --7700 sq. mi. In 2000, the zone was the smallest since 1988 -- 1700 sq. mi. WHY? --primarily because of very different weather conditions each year. Differences in nitrogen usage and practices, both point and non-point source, are extremely unlikely between these two years.
Yes, I strongly support efforts to reduce nitrate loading to the GOM, especially from agriculture, but I find it virtually impossible to use the two quantitative goals outlined in the draft plan to measure progress in attaining these goals. Perhaps models containing these non-controllable factors could be developed during the next few years to assist these quantitative yardsticks. To my knowledge these models do not exist presently.
Thanks for the opportunity to comment.
Dr. Gyles Randall, Soil Scientist
Univ. of Minnesota, Waseca, MN 56093
- co-author of CENR Topic 5 Report
- past chair of USDA/CSREES NCR-195 regional committee
"Mississippi River Watershed Nutrient Sources and Control"