09/05/2013 01:18 EDT | Updated 11/05/2013 05:12 EST

Who's Letting One of B.C.'s Most Imperilled Ecosystems Die?

The Coastal Douglas Fir zone (CDF) extends throughout the Lower Mainland's Georgia Basin and is recognized by conservation biologists as one of the most biologically unique and lush landscapes in Western Canada.

Early European explorers to the Georgia Basin described the area as a verdant and varied landscape of large, old fir forests, oak and arbutus woodland, bracken and camas-filled meadows extending along the south-eastern coast of Vancouver Island, throughout the Gulf Islands. The natural beauty, Mediterranean climate and abundant natural resources of the Georgia Basin sheltered First Nations peoples for thousands of years and it is now recognized as one of the most desirable places to live in our small world.

This is perhaps why it the CDF is now among the most imperilled ecosystems nationwide.

Not large to begin with - it's a 2,561 kilometres square area - the seasonally dry CDF ecosystem is now 49 per cent converted to human use with less than 3 per cent of its original "old growth" cover of over 145 year-old forest. There's also less than 10 per cent of historic oak woodlands remaining.

As a consequence, the CDF zone provides an uncertain habitat for 117 "species at risk" and 29 endangered plant communities. Despite its degradation, the CDF has yet to see a sustained, coordinated effort by government, non-profits and private land owners to ensure that relatively "intact" examples of our most treasured native landscapes are conserved for future generations.

The Nature Trust of British Columbia, an early leader in land acquisition in the region, is now helping change that fact. We are re-focusing attention on the CDF and facilitating strategic planning efforts aimed at conserving landscapes with high native species diversity, and restoring mature Douglas fir forests to old growth status over the coming decades. However, we will need to do more than acquire land, as much evidence shows "stewardship" is an imperative component to achieve these objectives.

Why? It is well-established that humans affect plant and animal populations directly via habitat conversion. But it is now also clear the "indirect effects" of humans are just as detrimental, such as the introduction of exotic species, or facilitation of "human commensal species," at the expense of vulnerable native animals.

Familiar examples include the introduction of mosquitoes to Hawaii, resulting in the extinction of 28 bird species. Closer to home, many biologists now point to the rise of urban and rural populations of small-bodied predators, such as raccoons, as threats to the persistence of many vulnerable bird and reptile species.

Small-bodied predators increase when humans eliminate large predators from landscapes, because wolves, cougars and other large predators can limit their population size. Our removal of once abundant cougar and wolf populations from the CDF has similarly resulted in the "release" of black-tailed deer populations, particularly those restricted to islands. As a consequence, high deer density is now a threat to the persistence of many species, including iconic members of the CDF and Garry Oak woodlands.

Many plants once abundant in forest and woodland habitats, such as great camas, fawn and chocolate lilies, onions and brodea, are now becoming scarce, particularly in the Southern Gulf Islands where cougars and wolves are largely absent.

Stewardship will be needed to prevent indirect human effects from reducing further the natural values that have drawn so many humans to the region. The Nature Trust of British Columbia's focus on the CDF is aimed at turning the tide of species and habitat loss in the region, and at building on our history of acquisition and stewardship in cooperation with the local communities. We believe the problem of species loss in the CDF is reversible and we're getting to work on proving that right now.