Where do the top three presidential candidates stand on the National Park Centennial Challenge? If omission is any indication, only one supports it.

Only Republican John McCain mentioned the challenge by name in answer to a question the National Parks Conservation Association posed to the candidates on park funding. The two Democrats in the contest, Hillary Clinton and Barack Obama, replied that they believe the National Park Service needs better funding, but didn't specifically refer to the Centennial Challenge as a way to get there.

Should we be surprised or disappointed? Probably not. After all, would you really expect two Democrats to endorse a Republican initiative during the heat of a presidential campaign? But in answering three questions posed by NPCA, the candidates at least cracked the door a bit on their thoughts about the national park system.

Air Pollution and the National Parks

All three voiced concern over how air pollution is sullying the air and resources of the national park system. Both Sens. Clinton and Obama pledged to eradicate weaknesses in the Clean Air Act they attribute to President Bush.

Sen. Clinton:

The Clean Air Act provides tools to reduce air pollution in parks, but the Bush administration has chosen to weaken these tools. I will reverse these rollbacks and put the Clean Air Act tools to good use to reduce haze and pollution in our parks. I will also rein in the pollution from coal-fired power plants by directing state utility commissions to demonstrate that the demand for power cannot be met through efficiency before approving a new plant; fund 10 large-scale carbon capture and storage projects; and require all new power plants to be capable of using carbon capture and storage technology when it becomes available. These acts will reduce emissions of sulfur dioxide, nitrogen oxides, and mercury from power plants, which is the most important step that we can take to reduce the harmful air pollution that is diminishing our national treasures.

Sen. Obama:

As president, I will restore the force of the Clean Air Act. I will fight for continued reductions in smog and soot, and continue my leadership in combating toxins that contribute to air pollution. Unlike President Bush, I will listen to my scientific advisers on air quality standards. And I will reverse the Bush administration's attempts to chip away at our nation's clean air standards and the integrity of our national parks. I will also protect roadless areas in our national lands.

Sen. McCain, on the other hand, made no mention of weaknesses in the Clean Air Act but rather pledged to work with all involved to improve air quality.

As responsible stewards of our National Park System, we are called to protect our natural treasures -- the land, water and air -- for the benefit of this and future generations.

With regard to air pollution, as president, I will ensure that the Clean Air Act is vigorously enforced. Where air pollution problems persist that degrade the park or visitor experience, my administration will work with all stakeholders-the conservation community, parks visitors, the public, and emitters - to establish agreements and processes to clean up the pollution in a manner that fulfills our vital stewardship responsibilities to our crown jewels and surrounding communities.

Funding The National Park Service Up to Its Centennial in 2016

On the question of funding the National Park Service, only Sen. McCain specifically referenced the Centennial Challenge, which is seen as a vehicle to funnel $3 billion in a mix of public and private funding into the parks by the Park Service's centennial in 2016. However, Congress has not yet passed legislation necessary to authorize the public-private matching proposal, and has not funded the program as President Bush suggested.

Sen. McCain:

As we look forward to the centennial of the National Park System, we have an excellent opportunity to highlight for the public the many threats and challenges our parks face - particularly the shameful backlog of vital maintenance and park protection projects. Focusing public attention and marshaling the support necessary to solve these challenges is predominantly a matter of leadership, and, as president, I will provide. I strongly support the establishment of a National Park Centennial Fund that would provide the resources needed to meet the operations and maintenance backlogs. Our objective must not be to establish the fund by the centennial; it must be to eliminate the backlogs and restore our parks well in advance of this historic occasion, and to ensure that today and for the next 100 years, our parks enjoy the resources, wise management, and attention befitting their importance to our country and the world.

Sen. Clinton:

It will be up to the next President, Congress, advocates like NPCA, the private sector, and all Americans to pull together to ready our parks for this important milestone. I believe that this effort starts with new funding for our parks. As President, I will propose significant increases in my budgets, and I will work with Congress to make those increases a reality. With an increased public commitment to our parks, I believe that we can more effectively reach out to the private sector to contribute to this effort. But increased funding by itself is not enough. We must tackle the maintenance backlog at the parks; we must encourage innovation and strive to better use science in managing our parks; we must reduce pollution and other threats to our parks; and we must make sure that our parks serve all visitors.

Sen. Obama:

I am committed to addressing the funding shortfall that the National Parks Service has experienced, and ensuring that by 2016, the National Parks Service centennial, the national park system has the resources it needs to meet its unmet maintenance and operational needs

What Do National Parks Mean to You?

The softball of the questions was the last one, in that it gave the candidates an open mic to describe what the national parks mean to them.

Sen. Clinton:

Our national parks are the crown jewels of America’s natural and cultural heritage. I have spent countless hours at our national parks, taking in the beauty and splendor they have to offer. To me, they embody the American spirit. From the majestic parks of the West, with their soaring mountains and plunging canyons, to the parks in the East, from the Everglades to Acadia, to the great monuments in our nation’s Capitol and the many other historical and cultural sites across our country ­ our national parks are all inspiring, each in their own way. What President Theodore Roosevelt said at the beginning of the 20th century remains true today: that we have the “great central task of leaving this land even a better land for our descendants than it is for us.” As we approach the 2016 Centennial, I will work as President to strengthen our national parks and to encourage all Americans to visit them to better appreciate our natural and cultural heritage.

Sen. McCain:

Our National Park System is another reason I’m so proud to be an American. Like so many Americans, I love our parks because their diversity, beauty, and timelessness feed the soul and inspire the spirit. They are a vital link to the larger forces of creation and the handiwork of our Creator. I have had the pleasure of spending a great deal of time at the Grand Canyon in my home state of Arizona, and enjoyed the privilege of working many years to protect the park, preserve its character, and enhance the experience that its visitors deserve. As an individual, our parks are a source of great personal joy and inspiration; as a national leader they are a cause that I’ve been proud to serve throughout my life in public service as they will be during my presidency, and the rest of my life.

Sen. Obama:

I have very fond memories as a kid of traveling to Yellowstone, marveling at the scenery, and chasing after bison, much to my mother's distress.

But when I think of my own connection to the earth, I think of my time in Hawaii, my birthplace, which is home to many national parks. I think those of us who grew up in Hawaii have a particular attachment to the land and understand how fragile it is. When you are snorkeling through the coral reefs, you realize that a slight change in temperature or increase in sediment and runoff could end up destroying it all and making it unavailable for your children. That is something you worry about.

My own experiences are precisely why I believe strongly that our national parks are one of America's most precious treasures, and that we should do all we can to ensure that they are properly maintained and available for all Americans to enjoy.

You can read the entire text of the candidates' answers, including their thoughts on global warming, at this site.