There is something amazing going on in the Land. And it disproves the old P.T.Barnum dictum that no one ever lost money underestimating the intelligence of the American people. It also shows how fast the public can get motivated if it sees a threat to its values.

I am talking about the recent emergence of urban sprawl as an issue of major political dimensions at local, state and national levels. It is my perception that there has been more action on this issue in the last three months than in the 25 years preceding. A lot of the debate centered around the recent elections, and when many races turned on the issue, there were about 200 related ballot initiatives nationwide, nearly all of which passed.

Environmental groups had been pushing the issue of uncontrolled development for years, often tying it to the virtues of a simpler and less consumptive lifestyle. Pitched that way, few thought it would find much fertile ground with an electorate enamored by their large lots, shopping centers and sport utility vehicles.

But all that changed virtually overnight. Something struck a chord with the public. The commentators seem to tie it to a growing sense of the loss of community and livability, with more and more time devoted to auto travel, with children tied to school bus schedules, and with nature and open space consumed by more and more development. Whatever its causes, it is clearly broad-based and growing.

We have seen in recent years the emergence of “neo-traditional” communities and increased interest in older areas of the cities and inner suburbs, but these have been considered “niche markets” designed to appeal to a few. What we are now seeing seems like more of a wholesale assault by the public on unmanaged growth at the urban fringe.

The elements combine in different ways in different communities, but they focus around one or more of three broad ideas — protecting open space, establishing urban growth boundaries, and encouraging in-fill development in existing communities.

These are the same ideas that drove the last great nationwide effort to deal with growth management in the early ’70s, but there are a couple of new twists. That effort was strongly focused on state-level controls over local actions; much of the current effort is directly at the local level. And the tools this round are more sophisticated; scenic easements, development rights purchases and trades, and innovative clustering and subdivision design have all come of age.

Another interesting fact is how the issue of sprawl cuts across party lines. Here in the Chesapeake watershed, the word is that Democratic Maryland Gov. Parris Glendening’s successful re-election was tied in part to his record as an advocate of “Smart Growth.” But the largest victory among the ballot initiatives was in New Jersey, where Republican Governor Whitman got strong voter endorsement for her proposal to save one half of the remaining open space in the state. In more than two dozen states from Rhode Island to Florida to California to Alaska, the initiatives cut across party lines, and the number of proposals for containing sprawl lost could be counted on the fingers of one hand. In other states like Tennessee, the legislature acted before the election to put new laws in place.

Closer to home, in addition to the Maryland governor’s race, the desire to contain sprawl led to Republican victories in Calvert County, Maryland and Prince William and Fauquier counties, VA, and Democratic wins in Anne Arundel County, MD. In addition to these election results, there are many other efforts to look at the issues of growth and development, including the Piedmont Futures meetings in Virginia and the “21st Century Report” in Pennsylvania.

So, how does all of this activity and awareness affect the Chesapeake Bay? There are a number of important intersects. The basic job of restoring the Chesapeake involves reducing nutrient loadings, namely nitrogen and phosphorous. And urban sprawl makes that job harder in a number of ways.

First, it causes the permanent and unnecessarily extensive loss of forests to development, highways and even agriculture displaced by development. Forests are our most efficient absorber of nutrients by far. Although forests currently cover 60 percent of the drainage area of the Bay, they deliver only 17 percent of the nitrogen and a mere 3 percent of the phosphorous to the Bay. Once they are removed, the forests are nearly impossible to replace, and the uses that take their place generate and pass through much higher levels of nutrients.

Second, nearly a quarter of the nitrogen entering the Chesapeake comes from the air, and about half of that is from automobiles. Those automobiles are concentrated in the developing areas of the watershed close to the Bay, where they do the most damage. Even though we have made great progress as a nation in reducing the pollution produced from individual autos, urban sprawl has meant that the number of vehicle miles traveled in the Chesapeake region has gone up at a rate four times greater than population growth. So even as our cars have become cleaner, our development patterns have caused us to drive more and more, and to generate more nitrogen pollution.

Finally, large lot subdivisions scatter over the landscape in ways that exacerbate nutrient pollution. Lawns use much more fertilizer and pesticides per acre than the forests and farmlands they replace. The roads and driveways that serve the subdivisions, and even rooftops, are all impervious and cause rainwater to wash off, turning creeks into flashing storm drains. In short, the land and the streams lose their ability to absorb the shocks and thus pass them on to the Bay.

For all these effects, we have reason to celebrate the public’s discovery of the costs of sprawl. It has even been suggested by Timothy Egan in the New York Times that Tom Wolfe’s new book about a developer in Atlanta may do to sprawl in the ’90s what “Bonfire of the Vanities” did to skewer Wall Street greed in the ’80s.

Whether this is a short-lived “window of opportunity” based on a wistful search for a past that never was, or a “sea change” in the way people think about how they want to live and what kind of community they want their children grow up in, it is a heartening shift in the body politic. And so long as it keeps up, the Bay will be a beneficiary.