Dr Taft: The question is: If the trend is real, is it 
due to a natural progression of things in the system or can it 
be attributed to anthropogenic effects or man's effects on the 
system. 
I think certainly that there's a small component of natural 
degradation in the system. However, I think that the major 
changes that we have seen parallel not only the growth in the 
watershed, but the changes in agriculture in the watershed. 
Specifically, with respect to nutrients, the amount of land and 
crops has not changed very much, as Bob showed earlier this 
morning. But the intensity of that land use such as getting 
three crops in two years instead of one crop per year, the sharp 
trend in the increase of soluble nitrogen fertilizers which has 
increased while the total nitrogen suspension since 1955 has 
doubled, and the use of soluble ammonia fertilizers has gone up 
ten or fifteen times. So the growth, the way we're using the 
land, all parallel the changes that we see and can be 
associated, correlated, with the changes that we see in the 
system. But we don't have as good a historical data set to make 
all of the exact connections that we would like to. 
Dr. D'Elia: Thank you very much. 
(Tools for assessing changes in the system are being 
developed in the form of monitoring programs to collect 
appropriate data sets and mathematical models to help evaluate 
and fill gaps in the data sets. Since this talk was delivered, 
better data have been collected, a steady-state model for the 
Chesapeake Bay has been developed and used, and a real time 
three-dimensional model has been commissioned for development. 
With these tools in hand, managers should make more informed 
decisions and have the ability to both project and actually 
assess the results of those decisions.) 
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