One of B.C.’s Most Endangered Ecosystems

[Excerpts from a report by Trevor Goward, Third Canyon Consultants and Andre’ Arsenault, Ministry of Forests Research Ecologist]

In recent years, temperate oldgrowth rainforests have been the subject of considerable study and debate by ecologists, foresters and environmentalists. By contrast, much less attention has been directed to oroboreal oldgrowth rainforests, their inland counterparts. This is unfortunate: whereas the temperate rainforest phenomenon occurs in at least six different regions of the world, oroboreal rainforests are unique to south-eastern British Columbia, where they occupy a discontinuous longitudinal band between 51 degrees North and 54 degrees North. Oroboreal rainforests are further restricted to the wettest subzones of the Interior Cedar-Hemlock Zone, especially the ICHvk and are well represented in only a half dozen drainages.* Regions combining comparable humidity and continentality are unknown elsewhere in the world.

Many of British Columbia’s oldgrowth forest have originated as a result of fire and are probably no older than the oldest trees within them. By contrast, environmental continuity in other oldgrowth forests may actually considerably pre-date the oldest trees. Such forests may be termed “antique.” Recent research indicates that antique forests contain richer assemblages of oldgrowth-dependent organisms, especially epiphytic lichens, than do younger oldgrowth forests. Antique forests thus appear to be of critical importance for the long term maintenance of regional biotic diversity. Because such forests are geographically much more restricted than younger oldgrowth forests, antique forests deserve special consideration as candidates for protected status.

Oroboreal rainforests closely resemble coastal rainforests in the complexity of their architecture, as well as in the lushness of their respective understories. On the other hand, observations on size and age structure reveal striking differences in regeneration dynamics. For example, temperate rainforests are characterized by high densities of younger trees, whereas low densities are more typical of the oroboreal rainforests.

Ecologists are only now beginning to study the oroboreal rainforest phenomenon, yet already it is clear that future studies will considerably deepen our understanding of the working of oldgrowth forests as a whole. Given the small geographic area occupied by antique oroboreal rainforests (most are restricted to valley bottom localities, where fire is rare), current rates of harvest place them among British Columbia’s most endangered ecosystems. They also represent one of very few ecosystems entirely restricted to this province. A concerted effort should be made to set aside such forests wherever they exist.

* These six drainages are the Upper Adams River, Wells Gray Park, Upper Seymour River, Robson Valley, Cariboo Mountains, and the Cummins River Valley.