Imagine Yosemite National Park without Yosemite Fall. Or Glacier National Park without glaciers. Or Old Faithful becoming less faithful.

These are just some of the impacts a changing climate could bring to bear on our National Park System. True, not all the impacts will be easily visible or take root overnight. Some perhaps not in the next 50 years. But as the globe continues to warm, the impacts likely will be more and more widespread across the system.

Already there are predictions that changes in precipitation could influence the groundwater that helps fuel Old Faithful in Yellowstone National Park. In the last decade alone drought has been blamed for slowing Old Faithful's eruptions from every 71 minutes to 91 minutes.

Already Yosemite Fall, as the accompanying photo (taken October 8) shows, goes dry in the fall. Shorter winters and less snowfall could cause the Yosemite Valley's iconic falls to endure longer and longer dry spells. Meanwhile, in Montana, Glacier National Park's rivers of ice, as many have heard, are now predicted to be gone by 2030 at the latest due to warming temperatures.

Melting of ice at the two poles is expected to raise sea levels, something that would inundate places such as Biscayne National Park, of which 95 percent already is under water, and Dry Tortugas National Park. Denali National Park and Preserve also could see its glaciers shrink drastically, if not completely, and its permafrost likely will come out of its deep chill.

Exactly how the National Park Service responds to these threats remains to be seen, though agency officials are trying to sort it all out. Contributing suggestions to the agency's own research and decision-making is the U.S. Environmental Protection Agency, which back in June finalized its Preliminary Review of Adaptation Options for Climate-sensitive Ecosystems and Resources. Chapter 4 of that hefty document (attached below) applies specifically to national parks. Among its suggestions is the following:

Climate has fundamentally defined national parks. Climate change is redefining these parks and will continue to do so. Rather than simply adding and ranking the importance of climate change against a host of pressing issues, managers are wise to begin to include climate change considerations into all activities and plans. There are a number of short-term approaches that may help to provide resilience over the next few decades. These include reducing habitat fragmentation and loss, invasive species, and pollution; protecting important ecosystem and physical features; restoring damaged systems and natural processes (recognizing that some restoration may not provide protection of dynamic systems); and reducing the risks of catastrophic loss through bet-hedging strategies such as establishing refugia, relocating valued species, replicating populations and habitats, and maintaining representative examples of populations and species. Short-term adaptation may involve prioritizing resources and determining which parks should receive immediate attention, while recognizing that the physical and biological changes that will accompany warming trends and increasing occurrences of extreme events will affect every one of the 270 natural national parks in the coming century.

Of course, before the Park Service can fully tackle climate change, it has to understand exactly what exists on its 84-million-acre landscape and how changing climate could impact those resources. "Protecting natural resources and processes in the near term begins with the need to first identify what is at risk," reads a section of the EPA report. "The next steps are to define the baselines that constitute 'impaired' in a changing world, decide the appropriate scales at which to manage the processes and resources, and set measurable targets of protection."

Across the national parks more than a few managers already are at work trying to sort through these issues. The Traveler will bring you examples of these efforts in the months ahead.

Now, the National Park Service doesn't need to approach this problem-solving in a vacuum, as the United States certainly is not alone in grappling with climate change. Great Britain has quite an extensive national park system that also is being confronted by climate change. Some believe it must undergo extensive change to cope with changing climate.

Here are some snippets from an article that The Observer of London ran last December:

Britain's National parks - enjoyed by 100 million visitors a year - must undergo a conservation revolution if they are to meet the challenges of climate change and the introduction of new farming practices.

This is the stark warning of leading environmentalist Adrian Phillips, who has warned the National Parks Societies that our most precious landscapes will have to adapt in the near future. Phillips wants planners to encourage small renewable energy projects, such as wind turbines, hydroelectric schemes and solar water heaters. He warned that new planning laws will have to be introduced to make new buildings carbon-neutral and the parks entirely so.

The government also seems to have woken up to the conservation value of national parks. Despite deep cuts in the government budget planned in the medium term, Rural Affairs Minister Jonathan Shaw announced last week that funding for national parks would increase by 10 per cent over the next three years, marginally above inflation.

A showcase for how Britain's national parks could develop in the future already exists in Cumbria. Ennerdale runs east to west about 10 miles from the coast. In 2000 the National Trust and the Forestry Commission agreed to try a new method of management in a valley degraded by inappropriate conifer plantations.

The idea was to allow natural processes a much greater say in how the valley changed. Two years later the third major landholder in the area, United Utilities, joined the project. The valley wasn't abandoned, but managed at a lower level of intensity. Sheep are being replaced by fewer, larger herbivores such as Black Galloway cattle and red deer. Wardens monitor the cattle via satellite to track their movements but they calve alone and are allowed to roam freely.

(Richard) Leafe (the chief executive of the Lake District National Park) argued that building this 'ecological resilience' is the idea to reinvigorate national parks not just naturally, but socially too: 'This process takes farmers, and that means communities, shops and post offices and all those things. Otherwise we'll end up with a ghetto where only the rich live and the people who look after the place and make it thrive travel in great distances by car to do it.'

Of course, Great Britain's national parks are managed a bit differently than those in the United States, as often they encompass whole towns and farms. Still, perhaps the two countries' park managers could benefit by comparing notes on how to cope with climate change.

Climate change will surely exert a wide array of pressures on the National Park System. Moving forward, it will be interesting to see how those impacts are manifested and how the National Park Service responds.