Last modified: Tuesday, May 13, 2008 12:18 AM EDT FLANAGAN: Good day for earth The kids ought to know ... that riding a seesaw was a good thing to do on Tuesday. If enough of you had gotten together for an old-fashioned tug o' war, that also would have been a great way to celebrate Earth Day. The skills learned in such pastimes will be useful in your lives ahead. When the first Earth Day was held in 1970, it ushered in a new environmental movement. There was some expectation that this was a war to be won. I was 21 back then, and I'm certain that I wasn't the only one who felt that way. And goodness knows, big strides have been made in improving the environment since then. Back then, black smoke was a common sight, whether it was coughing out of the tailpipes of cars burning leaded gas or spewing out of industrial smokestacks. The Ten Mile and other local rivers were sometimes described as open sewers; maybe that was an exaggeration, but it wasn't over the top by much. Lead-free gasoline and industrial regulation have remedied those problems to a large extent. Recycling of household waste has become a common practice around the area. But it would be folly to think the war has been won. Many of the old problems linger - some power plants, for instance, continue to emit hazardous waste under politically protected "grandfather rights." While the worst excesses of strip mining of coal were brought under control, a new practice of mountaintop removal has come into vogue. They take the tops off of pretty mountains to make it easier to get the coal that is sent to those power plants. Some solutions bred new problems. Ethanol, a form of alcohol, has been added to gasoline as one means to stretch the petroleum supply, but is now reason for concern about the added costs of gasoline and the likelihood of soil depletion from all the additional corn being grown. Wind power is proposed as a way to reduce our reliance on coal or oil-fired plants. While I don't agree with the argument that has been put up against a wind farm for the Nantucket area, there is no denying that it will not be an improvement of the view. Other fuels, such as biomass, will present their own problems even as they offer an alternative to petroleum. Will we ever win this war? I don't think so. But then again the environmental movement has shown itself not to be a war so much as it is a continuing struggle to achieve a balance - like on the seesaw - between satisfying needs for energy while guarding the planet's finite resources. Forces committed to development will forever be engaged in a tug of war with those committed to preservation and conservation. Play on, kids. Just tell the teacher or your parents that you're doing your homework for your future role as an involved citizen. MARK FLANAGAN (mflanagan@thesunchronicle.com) is Opinion Page editor of The Sun Chronicle.