BIODIVERSITY OF BRITISH COLUMBIA: AN OVERVIEW

Hornby Island, BC, photo by Brian Klinkenberg

 

 by

Dick Cannings

British Columbia--bordered on the west by the rich waters of the Pacific Ocean, on the southeast by the Rocky Mountains and the northeast by fringes of the prairies, on the south by arid valleys and on the north by arctic-alpine tundra--is home to more species of living things than any other Canadian province.  Although the reasons for the existence of this rich assemblage of species can be attributed largely to topographic and climatic diversity, other factors are in British Columbia’s favour as well.  The intricate topography of the province juxtaposes mountains, plateaus, valleys and coastal plains with their associated lakes, rivers and wetlands to form a myriad of complex and varied ecosystems. 

Some species of animals and plants are endemic to British Columbia, meaning that they are not known to occur anywhere else in the world.  Perhaps the best known of these is the Vancouver Island Marmot, a large, chocolate brown relative of the woodchuck found only on the high mountain meadows of Vancouver Island.  Fewer than 100 of these animals survive, making it one of the rarest mammals in the world.  One hundred and sixty-eight insects are endemic to British Columbia, as are six plant species, most of them restricted to the coast.

 

Flammulated Owl, photo by Dick Cannings

 

Two systems that identify and map British Columbia’s ecological zones are widely used today.  Vladimir Krajina developed a system of biogeoclimatic zones (BEC zones), which are areas characterized by climatic factors and defined according to the tree species that dominate in climax forests within them.  Examples of the fourteen zones are the Coastal Western Hemlock Zone along most of the coast, the Ponderosa Pine Zone in dry Interior Valleys, and the Spruce-Willow-Birch Zone between the boreal forests and alpine tundras of the far north.  The second system is the ecoregion concept developed by Dennis Demarchi, in which British Columbia is divided into 10 ecoregions such as the Southern Interior Mountains in the Kootenays, the Boreal Plains around the Peace River, and the Georgia Depression, which includes the southwestern coast of Vancouver Island and Lower Mainland.  Both classification systems have many smaller categories grouped below the main categories.

British Columbia has a rich marine environment, home to several giant species including the largest octopus, sea star and chiton in the world.  Cold, turbulent waters surge through narrow passages, bringing nutrients to the highly productive coastal ecosystem.  The nutrients feed a soup of tiny plants, the phytoplankton, which in turn are eaten by clouds of shrimp and other small invertebrates, the zooplankton.  As coastal waters warm up in summer, the phytoplankton are sometimes dominated by dinoflagellates to create a red tide. 

 

Sagebrush Grassland, photo by Steve Cannings

 

The coastal environment is as diverse as the terrestrial environment.  In sheltered, rock-bottomed bays, kelp forests sway in the waves, sheltering schools of fish and many species of invertebrates on the ocean floor.  Shallow, sandy or muddy shorelines are often characterized by eel-grass meadows, underwater prairies of waving grass that host a unique community of animals and attract thousands of waterfowl, including Brant geese, every year.  Many offshore islands are breeding grounds for millions of seabirds.  Auklets, murrelets, murres, puffins and storm-petrels burrow into the turf or lay their eggs on rocky cliffs in their annual contact with land.  Triangle Island, off the northern tip of Vancouver Island, hosts the largest number, including a million Cassin’s Auklets.

Two wildlife spectacles of note occur annually in British Columbia coastal waters.  In spring, Pacific herring spawn in huge numbers in bays and channels up and down the coast.  These concentrations bring in seals, sea lions, thousands of ducks, loons, grebes, gulls and other water birds, and help feed the Grey whales on their northward migration.  The second spectacle is the annual migration of salmon to their spawning streams.  As the schools of big silver fish leave the open ocean and pass through Johnston Strait and the Gulf Islands, Killer whales follow them in, providing unparalleled viewing opportunities.

 

Burrowing Owls, photo by Dick Cannings

The salmon swim inland, up the rivers and streams they were born in, to spawn and die, sometimes hundreds of kilometres from the sea.  Their deaths provide a tremendous bounty for land-based animals.  Bears, raccoons and other mammals feast on the bodies, while mergansers, goldeneye, dippers and other birds dive for the eggs and salmon larvae.  Thousands of Bald Eagles gather each winter at sites of Chum and Coho salmon spawns, most notably at Brackendale on the Squamish and Cheakamus rivers and at Chehalis Flats on the Harrison River. 

Salmon runs are one small reason why the temperate rain forests along the coast of British Columbia are so productive.  The mild winters and abundant rainfall are big factors, of course, although the plants have to deal with poor nutrient levels at most sites.  Some of the tallest trees in the world grew along the coast, and a few huge Douglas-firs, western redcedar, western Hemlock and Sitka spruce remain.  Western Hemlock forests produce about 5 tonnes of plant material per hectare each year, and some very rich sites produce more than 30 tonnes per year. 

 

Yew Lake, BC, photo by Gerald and Irmgard Carter

 

In these forests of giant trees, some of the most important organisms are very small.  Fungi are essential elements of the ecosystem; some species connect with the roots of the trees to provide the trees an extra boost in obtaining nutrients in return for sugars produced in the greenery above.  Other fungi team up with algae to form lichens, once thought to be benign curiosities, but now known to be important providers of nitrates to a nutrient-poor ecosystem.  Important vertebrates include tiny salamanders, living at a density of about 200 per hectare, and Northern flying squirrels, which eat lichens and fungi, spreading their valuable spores through the forest.

Along the southeast coast of Vancouver Island and on the Gulf Islands, winter rainfall is considerably less and the summer drought stronger.  Here the natural forest is an open savanna of Garry oak, arbutus and Douglas-firs.  This habitat is one of the most endangered ecosystems in Canada.  At higher elevations in the Coast Mountains, the winter rains turn to snow in winter, and the rainforests become snow forests.  Mountain hemlocks, yellow cedars and amabilis firs manage to germinate and grow in forests where it is common to have 5 metres of snow or more on the ground at once, often lingering into July.  With very little chance of summer forest fires or other large disturbances, these are ancient forests filled with ancient trees.  One Yellow Cedar on the Sechelt Peninsula’s Caren Range was 1824 years old.

 

Sandhill Crane and chick, photo by Gerald and Irmgard Carter

 

Interior mountain forests are quite different, dominated by Engelmann spruce and wubalpine fir in the south and white spruce in the far north.  These forests are characterized by long, cold winters and short, warm summers.  They are similar in many ways to the boreal forests that ring the northern hemisphere, their understories characterized by plants of the heather family--for example blueberries, huckleberries, rhododendrons and false azaleas.  Much of the mountain and boreal forests of British Columbia are now covered by lodgepole pine, a species that needs high temperatures to open its cones and cleared areas to germinate in full sunlight.  Both needs are met by forest fires, which have cleared thousands of hectares of the Interior over the last century.  Another species that benefits from fire is the Trembling aspen.

The dominant animal in spruce forests is the Snowshoe hare, which has an amazing 10-year population cycle.  When the hares are abundant, their predators--Lynx, Great Horned Owls, Red Fox, Coyotes, Northern goshawks and others--increase in population as well.  This increase in predators drives down the hare population after two years, and numbers remain very low until they surge upwards about eight years later.  There is some evidence that the population increase is linked to climate changes locked into the 10-year cycle of sunspot activity.

Low elevation forests in the southern Interior are dominated by Douglas-fir and Ponderosa pine, with Western larch growing in moister areas.  The southern interior valleys have short, cool winters and long, hot summers, and these forests have an open, grassy understory.  Indeed, as one moves down in elevation, this becomes a parkland environment in pure ponderosa pine stands.  These are forests shaped by fire; both the pines and Douglas-firs have thick bark to protect them from ground fires that periodically clear out shrubs and small trees.  The larch, like the Lodgepole pine, needs fires to create the bare soil it needs to germinate.

Ponderosa pine forests in particular have a number of birds restricted to them.  The White-headed Woodpecker, Canada’s rarest woodpecker, is found only in the pine forests of the south Okanagan.  Pygmy nuthatches are one of the commonest birds in these forests and hardly ever seen in any other habitat.  The Flammulated owl, a small insect-eating species, is locally common in mixed Ponderosa pine and Douglas-fir forests.

Long-billed Dowitchers, photo by Gerald and Irmgard Carter

In the valley bottoms of most southern Interior valleys, from the Fraser and Thompson through the Okanagan and in the East Kootenay, the summers are too hot and dry to allow tree germination.  Here the natural ecosystem is a semi-arid grassland dominated by bunchgrasses and shrubs, notably the big sagebrush, rabbitbrush and antelope-brush.  Brittle prickly-pear cactus is common, and the list of animal species sounds very desert-like:  scorpions, black widow spiders, rattlesnakes, and even pigmy short-horned lizards. 

The grasslands of British Columbia have been divided into three groups, roughly based on elevation.  The Lower Grasslands are characterized by bluebunch wheatgrass, often growing with big sagebrush, mostly found in the Thompson-Okanagan area.  The Middle Grasslands, dominated by bluebunch wheatgrass and Sandberg’s bluegrass, have few shrubs, usually common rabbitbrush, and are typical of the Nicola Valley.  The Upper Grasslands are usually dominated by fescues, but on the Cariboo and Chilcotin plateaus wheatgrasses and needlegrasses are important species.

 

Prickly Pear Cactus (Opuntia fragilis). Cacti are readily dispersed

throughout suitable habitat. Photo by Brian Klinkenberg.

 

Much of British Columbia’s native grasslands have been converted to intensive agriculture, and the Antelope-brush grasslands of the south Okanagan are considered one of Canada’s four most endangered ecosystems (along with the Garry oak savanna mentioned above).

The other treeless environment in British Columbia is of course the alpine tundras on the mountaintops throughout the province.  The treeline in the coastal mountains is relatively low, usually around 1700 m, set by the tremendous amount of winter snowfall that in many years does not melt until July if at all.  Alpine meadows on the coast are dominated by sedges and low shrubby plants of the heath family such as mountain-heathers and crowberries.  Interior treelines are generally set by temperature, especially the length of the summer growing season, and occur at about 2100 m elevation in the south.  Most southern Interior mountains have extensive subalpine meadows, created by various combinations of fire, climate change and , locally heavy snowfall.  These meadows are famous for their midsummer flowers, with huge tracts of red paintbrush, blue lupine, yellow arnica and white valerian.

Kinnikinnick and phlox, photo by Gerald and Irmgard Carter

Animal life is scarce but easily visible; typical birds include ptarmigan, Horned Larks, American pipits and Gray-crowned rosy-finches.  Insects from butterflies and beetles to flies can be locally abundant on mountain-tops as they gather in summer in hill-topping mating rituals.

Most of the highly diverse natural areas of British Columbia coincide with areas that have been heavily populated and modified by humans--the southern valleys and coastal plain.  Ecosystems that are particularly vulnerable are wetlands, riparian woodlands (those habitats along streams and lakeshores) and grasslands.  Old growth forests throughout the province are rapidly diminishing in size and number; in many places only small remnants can be found.  Species that need these forests for survival are becoming very rare.  The most famous of these, the Spotted owl, has only about 50 individuals left in British Columbia, but others are affected as well.  Environmental issues around the marine environment in British Columbia generally deal with pure overexploitation.  Sea otters and whales were almost eliminated in the early years of European exploration and settlement, but overharvests have continued with salmon, herring, abalone, halibut and many other species. 

 

Reprinted with permission from

The Encylcopedia of British Columbia, Copyright Harbour Publishing

[Francis, Daniel (editor). 2000. The Encyclopedia of British Columbia.  Harbour Publishing.  806 pages.  $49.95. Available locally, or through Amazon.com.]