Ecology of the Forest

Rainshadow Forests

Between the ocean and mountains on the east side of Vancouver Island is a broad, forested plain known as the Nanaimo Lowlands.  Forests in this area are different from rest of the island because the mountains shield the Nanaimo Lowlands from much of the rain, causing a “rainshadow” effect.  Unlike the more common rainforest environments on Vancouver Island, this rainshadow area supports forested ecosystems that are adapted to this drier and warmer climate.  Climate scientists classify this area as “sub-Mediterranean”.

The type of rainshadow forest ecosystems we find here, are naturally rare on our planet.  They are dominated by a unique combination of drought tolerant species such as Douglas-fir, Arbutus and Garry oak and only occupy a narrow band surrounding the Salish Sea and the Gulf Islands within it.  There are more different kinds of plants and animals here than anywhere else in BC and more over-wintering bird species than anywhere else in Canada.

Old-growth Recruitment

As recently as 150 years ago, this area was carpeted in old-growth “rainshadow” forests.  The dominant Douglas-fir trees commonly exceeded 250 years in age, and some were as tall as 94 meters (308 feet).  Decades of industrial logging have completely eliminated old-growth forests in the rainshadow environments of the Comox Valley.  Only a few individual trees over 250 years old remain.

Modern logging practises prefer to harvest young forests 40-80 years in age.  This means that old-growth forests (>250 years old) will never again be the dominant feature in this rainshadow landscape outside of parks.  Forests within our existing parks tend to be comprised of mature second-growth forests (80-120 years old).  These forests are now beginning to contain some of the habitat features found in old-growth forests.  Only about 4% of forests in the rainshadow zone are protected in parks.  This will not be enough to sustain old-growth dependant species in the long term.  We need to protect more land.

Unfortunately, by 2012 nearly all mature second growth forests in the eastern Comox Valley had been logged.  Conservation Biologists argue that there is an urgent need to protect younger second-growth forests (60-80 years old) as “old-growth recruitment areas” in our rainshadow zone.  This is exactly what the Cumberland Community Forest Society is doing.

Habitat

From coho salmon and coastrange sculpin in Perseverance Creek to cougars and Columbian black-tailed deer in the woods, Cumberland’s forests provide habitat for an immense number of animals. Each species has specialized requirements for cover, forage, nesting, denning and other necessities of life.  The complexity and diversity of habitats in the Cumberland Community Forest provides both general (coarse-scale) and specialized (fine-scale) habitat requirements.

Beta-diversity is a term scientists use to describe the diversity of coarse-scale habitats within a given landscape.  For example, landscapes that include open canopy forests, closed canopy forests, wetlands, rocky outcrops and cliffs, lakes and creeks have higher beta-diversity than landscapes that include only closed canopy forest.  Beta-diversity is relatively high in the Cumberland area which is important for many species.  For example, the rough skinned newt breeds in early Spring in aquatic environments such as ponds, lakes, wetlands and slow moving streams.  However, adults spend most of their lives in upland forests.  In particular, they require the moist environments of large rotten logs or a well developed leaf layer on the forest floor to survive.  The juxtaposition of wetlands and forest environments in the Cumberland Community Forest provide habitat for this species whereas one without the other would not.

Structural diversity provides a range of important habitats within any given ecosystem type at the fine scale.  For example, large diameter, standing, dead or partially rotten trees (wildlife trees) are critical for a significant proportion of forest birds.  In fact, over 80 species of vertebrate animals in BC depend upon wildlife trees.  They promote what is called “stand-level” diversity or alpha-diversity.   An example of a species that requires wildlife trees in the Cumberland forest is the Brown Creeper.  This little forest bird often nests behind slabs of bark which are peeling away from rotten, large diameter trees.  Without the right kinds of habitat structures in the Cumberland Community Forests, these forest-dependant birds could not survive here.  Protecting a mosaic of habitat types including forests, wetlands, riparian areas and creeks along with conserving the important habitat elements within those ecosystems is critical to ensuring the full suite of native plants and animals will remain in our landscapes over the long-term.

Species at Risk

Over 50 species are considered “at risk” of extinction or extirpation in the Comox Valley.  Extirpation is when a species has been eliminated from one area, but still occurs in other places within its natural range.  In Cumberland’s forests at least two species have already been extirpated: Western Screech Owl and Wolverine.  The Northern Goshawk and Marbled Murrelet also likely nested in Cumberland’s forests in the recent past but no longer do so.  These losses of species are often a result of intensive modifications to the landscape resulting from urban, suburban or agricultural development as well as resource use, including logging, mining, recreation and hydroelectric development.  Invasive species, pollution, hunting and fragmentation of the landscape by roads, powerlines, trails, pipelines or other linear features can also play a part.  More often than not, it is a combination of these elements and their cumulative effects which are the cause of native species decline, extirpation and extinction.

Several species which still do occur in Cumberland’s forests are considered vulnerable to extinction or extirpation by the BC government.  These include the Northern Red-legged frog, Pacific Sideband Snail, Coastal Cutthroat Trout and the Olive-sided Flycatcher.  Protecting important habitats such as the riparian (streamside) areas of Perseverance Creek is the best thing we can do to make sure that species at risk will continue to call Cumberland home.

Endangered Forests

The rainshadow ecosystems which occur on eastern Vancouver Island, the Gulf Islands and the Sunshine Coast are “endemic” to (only found in) this part of the world.  This area which is also referred to as the Salish Sea also happens to be where 80% of the BC populations lives, and is an important economic region of Canada.  Over 49% of the landscape has been converted to non-natural land cover such as urban, suburban, agricultural and industrial land uses.  Most of the rest has been subject to industrial logging.  Here in the sensitive “rainshadow” environments of the Comox Valley, only 5% of the land base remains intact after 150 years of European and Asian settlement.

There are 35 different kinds of terrestrial ecological communities described by science that occur in the eastern part of the Comox Valley.  Of these 34 (97%) are considered “at risk” by the BC government. Eleven different kinds of forested ecological communities are known to occur in Cumberland.  All 11 types of Cumberland’s forests are “at risk” according to the BC government.  Some are considered “vulnerable to extinction” at the global scale, while others are globally “imperilled”.  These include the dominant or “matrix” forests that should be the most widespread in this area.  For example, forests co-dominated by Western Hemlock and Douglas-Fir with an understory dominated by Oregon Beaked Moss is the matrix forest that should be the dominant forest type in the Cumberland area and other upland areas of the Salish Sea region.  Globally, only 1% remains as old-growth forest as of 2004.  Over 90% has been lost to development or logged within the past 60 years.

The Cumberland Community Forest protects important areas of this forest type that will be allowed to reach mature and old-growth status over time, supporting the hundreds of species which rely on this ecological community as habitat.


Did you know?

Several species which still do occur in Cumberland’s forests are considered vulnerable to extinction or extirpation by the BC government.  These include the Northern Red-legged frog, Pacific Sideband Snail, Coastal Cutthroat Trout and the Olive-sided Flycatcher.  Protecting important habitats such as the riparian (streamside) areas of Perseverance Creek is the best thing we can do to make sure that species at risk will continue to call Cumberland home.