Efficient use of energy is necessary to preserve the environment, five distinguished environmentalists told a packed crowd at an Institute of Politics panel discussion at the ARCO Forum last night.

Energy seems cheap because people rarely consider its destructive effects, according to Heinz Professor of Environmental Policy at the Kennedy School of Government John P. Holdren, who was a panelist.

"We have consistently under-priced the environment," Holdren said. "The environmental cost has not been factored into the economic spreadsheets."

The featured expert at the panel was Denis Hayes, the creator of the first Earth Day and the chair and chief executive officer of the Earth Day Network, which organizes the event.

Other panelists were Veronica Eady, the executive director of Alternatives for Community and Environment, and a member of the board of directors of the Sierra Club; Robert Massie, executive director of the Coalition for Environmentally Responsible Economies; and Michael B. McElroy, Butler professor of environmental studies and chair of the Harvard University Committee on the Environment. Rep. Philip Sharp (D-Ind.) moderated the panel.

In his address, Hayes--who dropped out of Harvard Law School to organize the first Earth Day in 1970--spoke at length about the damage being done to the environment on a global scale.

"In the last few decades, we've stopped affecting our back yard and started affecting the climate," he said.

Hayes said the burning of carbon dioxide-producing diesel fuels is part of our habit of "running today's world on nineteenth century technology," which he called outdated and inefficient.

Hayes said he hopes to increase participation in Earth Day in 2000 to half a billion people. Publicity will be massive for the event, and will be carried out in places ranging "from the sides of cereal boxes to the Internet," he said.