An earthquake and a spring snowstorm in New York's Adirondack Mountains couldn't stop President Bush from marking the 33rd annual Earth Day there with a call for mandatory limits on power plant emissions blamed for acid rain in the region.

Bush dismissed a chorus of Democratic critics, including former rival Al Gore.

"Hadn't paid attention to him," Bush said of the former vice president he narrowly defeated in 2000.

His gray hair dampened by snowflakes, Bush shrugged his shoulders when asked about Gore criticizing his environmental record. "That's why I have not paid attention to him," he replied curtly.

Gore, dubbed the "Ozone Man" by Bush's father, is emerging from political hibernation to lead Democratic attacks on Bush's environmental stands. Speaking at Vanderbilt University in Tennessee shortly after Bush's remarks, he accused the White House of giving polluters undue influence.

Bush and his allies are "threatening to take us back to the days when America's rivers and lakes were dying, when the skylines were some days not visible because of the smog, and when toxic waste threatened so many communities around America," Gore said.

Though Bush refrained from confronting any of his critics, the presidential schedule here Monday reflected concern among advisers that he could be vulnerable on the environmental issue.

Before the cameras, Bush pounded nails into a tiny bridge spanning a creek, tested water from the churning gray Au Sable River, repaired a muddy trail and staked out a camp site. His face red with exertion, Bush pounded a 10-inch nail into a log with the flat side of a splitting maul — the sharp edge swinging within a whisker of the presidential forehead.

Mission accomplished, he hoisted the maul above his head and heaved a heavy sigh.

"Get them moving," he said with a laugh, pointing the tool to journalists. "That way I don't have to nail so many of these things."

Later, the president spoke to local residents who gathered at a Whiteface Mountain Lodge after White House aides moved the speech indoors because of chilly weather.

"For three decades, we've acted with clear purpose: to prevent needless and at times reckless disregard of the air and the water and the soil and the wildlife. This commitment has yielded tremendous progress," Bush said.

He said the 1990 Clean Air Act, stemming from his father's tenure, was a good start. "Now we should do more."

Bush has asked Congress to impose mandatory limits on industry production of three kinds of pollutants, and to let companies work out how to achieve them through a system of earning and trading credits. The pollutants are acid-rain-causing sulfur dioxide, smog-causing nitrogen oxide and mercury, a toxic chemical that contaminates waterways and goes up the food chain through fish to people.

His "clear skies" plan, which Congress has yet to consider, can "significantly reduce smog and mercury emissions as well as stop acid rain," Bush said.

Gore said the president was on the wrong track.

"Instead of working to reduce air pollution, the Bush administration's so-called `clean skies' initiative actually allows more toxic mercury, nitrogen oxide and sulfur pollution than if we enforce the laws on the books today," he said.

Environmental Protection Agency administrator Christie Whitman and White House press secretary Ari Fleischer, who accompanied Bush aboard Air Force One, said Gore had his chance to help the environment.

Still, Bush seemed to give the Clinton administration some measure of credit when he said environmental advances were made "at a time when our economy and population grew dramatically."

The dueling speeches, a replay of 2000 and perhaps a harbinger of 2004, came as Democrats seek to refocus voters on issues they cared about before the Sept. 11 attacks such as health care, education and the environment.

For the first time since the attacks, Bush appears at least slightly vulnerable in such areas. His sky-high wartime poll numbers have dipped slightly and his pollster at the Republican National Committee warned in a memo recently that "movement downward has begun."

Wavering on the Middle East has critics questioning the clarity of his foreign policy, and Bush's plan for oil drilling in Alaska was roundly defeated in the Senate last week.

His interior secretary, Gale Norton, joined the Earth Day celebrations Monday by dedicating a new Florida research center for invasive plants and releasing 10,000 exotic plant-eating bugs to help eradicate melaleuca trees, an Australian species infesting 400,000 acres of Florida's wetlands.

Fox News' James Rosen and The Associated Press contributed to this report.