The grizzly bear havens of Yellowstone, Glacier/Waterton, and Banff national parks are world famous. What is less well known is the land bridge that links these sanctuaries and keeps the parks' grizzlies healthy. Grizzly bears are wide-ranging creatures. They need as much as 500 square miles for hunting, and they must find mates from hundreds of miles away in order to sustain healthy family lines. Without the grizzlies being able to lumber along unprotected stretches of the Rockies, biologists say, the bear populations in national parks would become genetically isolated and unsustainable islands.

A similar fate would befall the wolves, cougars and other endangered animals that also need the land bridge to remain healthy. This land bridge may be the key to survival for several species, but it is almost as vulnerable as they are. The Alberta government is granting logging rights and sour gas leases (sour gas is an extremely toxic gas that is particularly harmful to the lungs and brain), and allowing off-road vehicle use in places designated as critical wildlife habitat, such as the Castle's Carbondale foothills. This region is critical for spring grizzly feeding as the bears come down from the mountains in search of early greenery. It is also vital elk habitat.

Although the Castle Wilderness urgently needs to be restored and protected, Shell Canada has proposed a six-year plan for up to six new sour gas wells in the Carbondale foothills. Shell Canada has already submitted license applications for the first two wells, and would like to start construction this summer.

Tell Shell Canada to halt plans for new sour gas wells in the Carbondale foothills of the Castle Wilderness.

FAST FACTS

Where: Alberta, Canada

What's at stake: Crucial migration route for bears and wolves

Threatened by: Natural gas drilling

Animals include: Wolves, grizzly and black bears, wolverine, lynx

- Old growth forests in the Castle-Bighorn support a rich variety of animal species. Some of the species found here -- such as the Canada lynx, marten and some bird species -- can survive only in the interior of large patches of old forest. There, fallen logs provide dens for hibernating grizzly and black bears, homes for red-back voles and marten, and stream debris that enriches fish habitat.

- The Castle-Bighorn is critical to the survival of several species because it provides a corridor through which populations remain connected, enabling them to repopulate when disease and other conditions thin their number in particular regions. For example, grizzly bears moving between Glacier National Park in Montana, the Flathead Valley in British Columbia, and northern populations in Kananaskis and Banff National Park, travel through the South Castle and West Castle valleys.

- Until the 1950s, the grizzly bear was abundant in southern Alberta. It was common to spot grizzlies in the Screwdriver Creek, Beaver Mines and lower Castle River area in the spring. They are rarely seen there today.

- The Castle is on a major migration route for bald and golden eagles, providing an abundance of nesting habitat for raptors, including golden eagles, red-tailed hawks, goshawks, great horned owls, and northern pigmy owls. Meanwhile, Castle wetlands have a healthy population of the uncommon and declining northern waterthrush, while its rivers and streams nurture a very vulnerable population of harlequin ducks.

- The Castle is home to 34 alpine lakes and tarns and is the birthplace of more than 26 major headwater streams -- their flows regulated by forest cover and numerous alpine and sub-alpine wetlands.

- Overlapping climate zones in the Castle have given rise to a wealth of more than 120 provincially rare plant species, allowing such western plants as tall huckleberry, thimbleberry, Oregon grape and large flowered fringecup to meet such southern plants as the red and yellow monkeyflower, beargrass, mariposa lily, big sagebrush and mountain hollyhock.

- In all, the Castle Wilderness is home to approximately 105 species of breeding birds, while 60 others migrate through the area, including rare flycatchers, woodpeckers, thrushes, vireos and warblers.

- The Bighorn region's rivers and streams sustain large populations of bull trout, cutthroat trout, brook Trout and mountain whitefish.