The Inland Rainforest
Northeastward moving air masses pick up moisture as they pass over interior valleys and dump this moisture when they run into the mountains of east-central British Columbia. Where the moisture falls as rain it creates the conditions for one of the wettest terrestrial ecosystems in the province. It is this ecosystem that has come to be known as the Inland Rainforest. Though there is some discussion surrounding the exact extent of the Inland Rainforest, it is generally restricted to the windward side of the Rocky and Columbia Mountains between 51°N and 54°N . The best example of this forest can be seen in the Rocky Mountain Trench between McBride and Purden Lake, southeast of Prince George.
Why is this forest so significant? First, the biological and structural diversity that distinguishes parts of the Inland Rainforest is unparalleled in the interior of the province. This is because the wet nature of parts of the Inland Rainforest prevents the frequent stand-replacing disturbance events such as wildfire that characterize many other forest ecosystems. In parts of the Inland Rainforest stands of trees can escape disturbance for hundreds—even thousands—of years, resulting in very old stands that have developed unique ecological characteristics. The oldest of these stands, where the age of the forest as a whole is significantly greater than the oldest tree, have come to be called ‘antique forests.’ Antique forest stands occur in discrete pockets where slope position, aspect, and moisture regime protect the forest from disturbance.
Second, the biological diversity of the Inland Rainforest has only recently begun to be explored at the ground and canopy level. To date, much of this research has been focused on arboreal lichens (lichens that grow on the branches of the canopy) and their relationship to forest age and structure. The emerging theory is that certain lichens depend on very old forest stands to provide the ecological and climatic characteristics necessary for their survival. These lichens may thus hold the key for assessing forest age and locating antique forests. Research in the Inland Rainforest is ongoing and researchers from the University of Northern British Columbia say that there is great potential for the discovery of species and ecosystems functions not found elsewhere.
However, as is the case with many of the province’s rarest ecosystems, not all is well in the woods. In addition to hosting incredible biological diversity, the Inland Rainforest is also one of the province's most productive forest ecosystems and is therefore subject to forest harvesting at an ever-increasing rate. This is especially true in the Prince George Forest District where salvage logging is rationalized by an outbreak of western hemlock looper. A much-maligned caterpillar, the looper affected hundreds of hectares of hemlock in the Robson Valley between 1990 and 1995.
The annual allowable cut from the Interior Cedar Hemlock biogeoclimatic zone in the Prince George area alone is 100,000 cubic metres (m3) of timber per year for the next 50 years. This is despite the fact that the Ministry of Forest’s calculated long-run sustained yield for the Inland Rainforest is 85,000 m3 per year. In most of the areas cut, cedar and hemlock stands will be replanted with spruce and Douglas-fir, eliminating the possibility of the forest ever regaining its original composition and associated biological diversity. In a worst case scenario, we could see the loss of over 70% of the Interior Rainforest by the year 2017.
Photo credits: Old-growth ICH forest, photo by Jocelyn Campbell; (top right) Fungal growth, photo by Darwyn Coxson (middle); Lobaria pulmonaria, photo by Darwyn Coxson (lower right)
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