Birds

Everybody recognizes starlings and English sparrows, of which the former is a serious predator of native birds' eggs and nestlings. The crested myna of Vancouver is merely an interesting curiosity. The other introduced birds in British Columbia, however, are "exotic" in both meanings of the word: alien, and interesting (even, to hunters and bird-watchers, exciting). They include the game birds northern bobwhite, California quail, ring-necked pheasant, chukar, wild turkey (now becoming abundant in parts of the East Kootenay), gray partridge and American black duck, as well as the non-game species, rock dove (common domestic pigeon), mute swan and Eurasian skylark. Of these, only the wild turkey and pheasant have established sizeable wild populations in the Columbia Basin. Some California quail, chukar and gray partridges can still be seen in the Thompson Okanagan, and may also occur in the Columbia Basin.

Fish

At the international workshop in April, 1998, "Toward Ecosystem-Based Management in the Upper Columbia River Basin," (Sustainable Fisheries Foundation, 1998) a common refrain echoed throughout was the need to avoid introduction of exotic fish species, and their parasites and diseases. Comments such as these were common in the summary report : "..water quality sufficient to maintain native fisheries..."; "...biodiversity of indigenous species maintained..." (emphasis added). Participants recognized that perhaps the only ecological good that came of the power dams was the restriction on upstream migration of non-native fish. Nevertheless, a number of exotics occur in the Columbia Basin. Both brook trout (actually, a char) and and brown trout have been widely stocked in the region. Carp, brown and black bullhead, pumpkinseed, smallmouth and largemouth bass, and black crappie are all in the Columbia River system, waiting for a chance to invade further upstream. These all have the potential to displace native sport fish; although, as warm-water fish, they may have trouble establishing large populations in the cold waters of the Columbia Basin. Walleye have already been reported from Arrow Lake; if confirmed, and if they establish a breeding population, woe betide the kokanee and trout populations which are already reeling from dam-related nutrient deficits.

Inappropriate inter-basin transfers of native fish have also interfered ecologically, for example, the stocking of Gerrard rainbow trout into Arrow Lake at the expense (apparently) of the native yellow-fin rainbow trout.

Mammals

So far, the potential impact of introduced mammals has yet to be felt in the Columbia Basin. Norway rats and house mice exist, but are not ecologically or economically troublesome. Dogs harass deer during harsh winters, and cats prey upon native songbirds, but their depredations are not regionally serious, so far as is known. Other species that may be, or may have been, present in the region include nutria (a muskrat-like rodent farmed for its fur), opossum, European rabbit, Eastern cottontail, gray squirrel and fox squirrel. As long as we have a good supply of native predators - river otter, lynx, bobcats, coyotes, foxes, cougar, etc. - exotic mammals are unlikely to gain a strong foothold in the Columbia Basin.

Invertebrates and Micro-organisms

Exotic invertebrates and micro-organisms cause a lot of grief to people and damage to ecosystems, but, ironically, some enhance our economy, while others offer ecological salvation.

On the down side, most or all of the diseases that affect human populations in the Columbia Basin were introduced with European explorers in the last century, with devastating effects on the native peoples of the region. Giardiosis ("beaver fever," caused by Giardia sp., a micro-oganism) and cryptosporidium are examples of newly introduced diseases, caused by micro-organisms, that can affect people. The same is true for wildlife: lungworm, introduced with domestic sheep, has caused massive die-offs in the Basin's bighorn sheep populations. In forests, the effects of the introduced white pine blister rust frustrate foresters throughout the region. There are also micro-organisms immigrating with domestic pets that can affect wildlife, such as the heartworm parasite of dogs which can affect wild canids (wolves, coyotes, foxes). Adamson (in Harding and McCullum, 1997, p. 9-6) suggests that, with global warming, a number of protozoan and invertebrate parasites could become troublesome, either because they are already present in B.C. and will breed or transmit more effectively in a warmer climate, or because the climate here will become suitable for new species to immigrate from the south.

Smith (1994) describes the causes and consequences of accidental and purposeful (for biological control) introductions of insects and a few micro-organisms. A major vector is as hitchhikers on nursery stock, by which route a number of insect pests arrived in Creston Valley orchards early in our settlement history. Examples are larch sawfly (Pristiphora erichsonii), European crane fly (Tipula paludosa), winter moth (Operophteron brumata), apple ermine moth (Yponomeuta malinellus), pear psylla (Psylla pyricola) and the cherry bark tortrix (Enarmonia formosana). Insects can cause economic damage, for example, by damaging crops and commercially valuable timber, and they can cause ecological damage by preying upon, parasitizing or competitively displacing native insects. The introduced seven-spotted ladybird beetle (Coccinella septempunctata), for example, being a generalist predator of aphids and other soft-bodied insects, has the potential to displace several of the 94 native species of ladybird beetles, many of which have more specific prey requirements. Smith (1994) lists 248 species of exotic beetles (7% of the 3,626 species of beetles in the province) and 67 species of accidentally introduced lepidopterans (moths and butterflies). Of purposeful introductions, she lists 111 insects, seven protozoan parasites, one fungus, two viruses and one bacterium introduced to control other insects; and 57 biological agents (insects, fungi and nematodes) brought in for biological weed control. Of this last group of weed control organisms, the majority are aimed at troublesome weeds of the West and East Kootenays: knapweeds, thistles, spurges, and toadflaxes (see Vascular Plants, below; and Grassland Ecosystems in the Ecosystem Diversity section).

Just to show that aquatic ecosystems are not immune to the depredations of non-native invertebrate species, the giant Gerrard rainbow trout of Kootenay Lake were nearly wiped out in part by the intentional but misguided introduction of non-native (to this system) mysids (shrimp-like organisms). See the Aquatic Ecosystem section for the full story.

Vascular Plants

Taylor and McBride (1977) found that 21.1% of all vascular plants to British Columbia were exotics. Alien plants are strongly associated with disturbed environments. Plants that colonize disturbed habitats must be able to disperse widely because, as the ecosystem recovers with the growth of other vegetation following disturbance, the environment becomes unsuitable for these species. Hence, their progeny must be able to find new, disturbed environments, and therefore these species have evolved mechanisms for wide dispersal, such as wind-borne seeds and animal-borne burrs (Sorensen, 1984). Many arrived in the grain or hay of livestock feed (Burcham, 1957), in ballast from ships, in nursery or agricultural shipments and on equipment such as tractors, hay mowers and harvesters (Montgomery, 1964). Because so many of these products move by rail, and the railroad beds provide ideal habitats for disturbed-site species, railroad rights of way have been major routes of introduction (Montgomery, 1964). Some, such as burdocks (Arctium lappa, A. minius) and hound's tongue (Cynoglossum officinale) are spread by furred wildlife, livestock and people. A few alien flowers, such as blackeyed susan (Rudbeckia hirta) are native to elsewhere in North America and have recently migrated to British Columbia on their own. Of course, many alien wildflowers escaped from cultivation in domestic gardens. The common elements in all of these alien flower and weed vectors are dispersal and disturbed sites.

Many plant species introduced into the Columbia Basin serve useful functions, or are aesthetically pleasing. English daisies (Bellis perenis) add interest to a lawn, for example, and many of the alien mints (Mentha citrata, M. piperite, M. spicata, M. rotundafolia) seem to improve a meadow or roadside wet spot with their blue or purple flowers and fresh scent. Even the much maligned dandelions (Taraxacum officinale, T. laevigatum and other species) are pretty on someone else's lawn. Lupines (Lupine arborus, L. densiflorus), clovers (Trifolium arvense, T. pratense and T. subterraneum) and a number of other wildflowers are routinely seeded to add nitrogen and prevent erosion on rights of way. Several attractive, introduced blue-flowered vetches (Vicia craccia, V. hirsuta, V. sativa), now wild, also perform this function. Some flowers, like the bright gold California poppy (Escholtzia californiana) are seeded for colour along urban roadsides. Ox-eye daisies (Chrysanthemum leucanthemum) are widely naturalized along roadsides and in meadows and fields. Other flowers, such as chickory (Cichorium intybus) which is especially abundant along roadsides in the dry interior, helleborine (Epipactus helleborine), crane's bill (Geranium molle), herb robert (G. robertanium), baby's breath (Gypsophila paniculata), dame's violet (or rocket) (Hesperis matronalis), yellow flag Iris (Iris pseudacorus), linaria (Linaria dalmatica), toadflax (L. vulgaris), mullien pink (Lychnis coronaria), purslane (Portulaca oleracea), have simply escaped from flower or herb gardens. As well as contributing to soil stability and development, introduced wildflowers provide seeds for birds and small mammals and nectar for hummingbirds and insects. However, these benefits are often a mixed blessing.

Notwithstanding the aesthetic, economic (slope stabilization, right-of-way maintenance, etc.) and even environmental benefits of alien wildflowers, they do take the place of, and in many cases directly displace, native flora. Moreover, they often alter the biological structure, and possibly the functions, of some ecosystems.

Range and Agricultural Weeds

Alien range and agricultural weeds of economic importance are listed under the Weed Control Act. The distributions of several important species are shown in the Grasslands section of the Ecosystem Diversity pages on this web site. Some wildflowers such as ox-eye daisy contaminate seed, hay or grain crops, reducing their value. Field bindweed (Convolvulus arvensis) causes mechanical damage to harvesting equipment. Canada thistle (Cirsium arvense), also alien, is one of the most troublesome agricultural weeds in British Columbia. A perennial, it can reduce grain yields by over 60% and may release toxic chemicals into the soil that inhibit other plants. Other alien weeds that cause agricultural damage in the Columbia Basin include nodding thistle (Carduus nutans), Russian knapweed (Acroptilon repens), perennial sow thistle (Sonchus arvense), plumeless thistle (Carduus acanthoides), leafy spurge (Euphorbia esula), common crupina (Crupina vulgaris), globe-podded hoary cress (Cardaria pubescens), sulphur cinquefoil (Potentilla recta), common tansy (Tanacetum vulgare), blueweed (Echium vulgare), rush skelton weed (Chrondrilla juncaceae), clustered dodder (Cuscuta approximata), common dodder (C. epithymum), wild oats (Avena fatua), velvetleaf (Abutilon theophrasti), orange hawkweed (Hieracium aurantiacum), and jointed goatgrass (Aegilops cylindrica).

Range weeds that affect grassland ecosystems have economic costs of reducing forage for livestock, in addition to effects on wildlife. The figures at left and below show the extent of serious and mild infestations of three of them: spotted knapweed, dalmation toadflax and leafy spurge. Many range weeds, not favoured for livestock and wildlife forage, degrade pasture and rangelands by out-competing native grasses and forbes for space and soil moisture and nutrients. Disturbance is usually associated with the initial infestation and later spread, although, once present, many weeds can compete with native species and infest healthy grasslands. However, other environmental factors, such as prolonged cool, wet periods or droughts, can also favour weed species (Sturko and Wikeem, 1990). Conversely, healthy, undisturbed grasslands can better withstand weed infestations without being dominated by them, and some native grassland communities are more resistant than others. For example, grassland communities dominated by rough fescue (Festuca campestris [F. scabrella]) seem more resistant to knapweeds than nearby blue-bunch wheatgrass (Elymus spicatus [Agropyron spicatum]) communities (Sturko and Wikeem, 1990). Once an infestation is established, the alien weeds can maintain environmental conditions suitable for themselves, with the possible result that the original climax ecosystem may be altered and productivity lowered.

Among the worst range weeds for Columbia Basin range lands are knapweeds, especially spotted knapweed, Centaurea maculosa, and diffuse knapweed, C. diffusa (Watson and Renney, 1974). They have caused major environmental deterioration and loss of beef production, as well as undetermined losses in grassland recreational and wildlife value. Canada thistle is also widespread in Columbia Basin pastures. It does not limit forage production except in local situations, such as around ephemeral ponds and wet meadows that dry in summer and receive heavy grazing, where it can form dense stands. It is also common in logged areas, where it (and other weeds) are introduced in the mud on the tires and tracks of logging vehicles, and by sheep used to control broad-leafed plants.

Other potential new problem weeds include wild four o'clock (Mirabilis nyctajinea), recently found at Spences Bridge; yellow starthistle (Centaurea solstitialis), not yet in British Columbia (1994) but identified in adjacent Washington and Idaho; and rush skeleton weed (Chondrilla juncea) which was recently (1994) found in the Kootenays and the North Okanagan (D. Blumenauer, pers. comm.).

A discussion of introduced rangeland plants would be incomplete without mention of alien grasses. Many different seed mixtures of at least 21 species of grasses and other plants have been used in British Columbia by different agencies for a variety of purposes, such as seeding rights of way (Nordstrom, 1984). These domestic species only become a problem if they invade natural habitats to the detriment of native species. Provincial government agencies and private ranchers have seeded crested wheatgrass (Agropyron cristatum) and other grasses and legumes to improve forage production and for rangeland rehabilitation. These mixes are seeded on some clear-cut areas in the interior, to provide livestock forage during the early reforestation period. Cheatgrass (Bromus tectorum), a very invasive annual grass, may have spread north from California, where it was introduced by early Spanish settlers with hay for their cattle, and has been associated there with widespread rangeland degradation. It sprouts from foxtail-type seeds dispersed by furred wildlife, grows quickly, sets seed in spring and then dies. Under heavy grazing pressure on the preferred perennial grasses, annuals such as this can gain a competitive advantage (Dasman, 1965). Until the 1940s and 1950s, cheatgrass occupied large areas of grassland in the Thompson-Okanagan and Cariboo regions. Cheatgrass has since declined considerably, probably in response to better grazing management, although pockets still remain in locally disturbed areas. Taken together, whether a cause of ecosystem degradation or merely a consequence of other disturbance, these alien weeds may considerably degrade the land's ability to support livestock and wildlife.

Costs of Control

No one can pretend that it would be possible to eradicate the long established and widely dispersed alien wildflowers and weeds from the province, but they are the subject of intensive control efforts in specific environments such as range lands, crops and urban environments. For example, control of knapweeds on range lands costs the province about $1,000,000 per year (Environment Canada, 1991). Various crop/range management, mechanical and biological control programs have limited the spread and helped reduced the damage caused by these weeds. This is accomplished with considerable interagency dialogue and co-operative programs between federal, provincial and regional district governments as well as non-government groups such as cattlemen's associations. The emphasis of current weed control programs is on containing existing infestations and preventing new ones. However, controls are not completely without impacts of their own. Herbicides such as Picloram, used to control broad-leaved weeds and to encourage grasses, may affect biodiversity of native plant communities within the treatment areas (Sturko and Wikeem, 1990).

The challenges now are to: continue to protect the health of grassland ecosystems through effective management, to prevent the further introduction and spread of exotic species wherever possible, and to carefully evaluate the effects of control options.

References