Threats to Biodiversity

Taking Nature’s Pulse concluded that of the six major stresses that threaten biodiversity in BC, the three most significant ones are ecosystem conversion, ecosystem degradation and alien species. And over all these threats is climate change which is already seriously impacting British Columbia and is the foremost threat to biodiversity.

Habitat Fragmentation

Ecosystem conversion and ecosystem degradation contributes to habitat fragmentation. Habitat loss from exploitation of resources, agricultural conversion, and urbanization is the largest factor contributing to the loss of biodiversity. The consequent fragmentation of habitat results in small isolated patches of land that cannot maintain populations of species into the future. Tweedsmuir Provincial Park, at 974,046 hectares, is British Columbia’s largest provincial park and is big enough to maintain much of the composition, structure and function of biodiversity within the protected area. However, smaller provincial parks, such as Buccaneer Bay at less than one hectare in size, will not be able to maintain all of its original biodiversity in isolation. Scientists report that the effect of habitat fragmentation on biodiversity may not be fully realized for decades after habitat is degraded. Therefore, habitat connectivity must be considered in current management practices to prevent the devastating effects of fragmentation on biodiversity.

Exotic Species Introductions

Infestation by alien species, such as the Codling Moth, is also a major threat to BC ecosystems. The intentional and inadvertent introductions of a wide variety of species to ecosystems in which they do not belong have resulted in ecosystems that differ radically in structure and function from those originally present. Exotic species are typically introduced into ecosystems without their co-evolved predators and parasites, which enables an alien invader to out-compete native species with similar ecological requirements. In British Columbia, plants such as Knapweed, introduced to arid grasslands, and Purple Loosestrife, introduced to marsh and riparian areas, are rapidly becoming dominant plant species in their respective ecosystems. The interactions between native species are altered or destroyed by these exotic species, and can result in the loss of native biodiversity.

Pollution

Atmospheric and hydrologic pollution have far-reaching negative effects on biodiversity. Pollution from burning fossil fuels such as oil, coal and gas can remain in the air as particle pollutants or fall to the ground as acid rain. Acid rain, which is primarily composed of sulfuric and nitric acid, causes acidification of lakes, streams and sensitive forest soils, and contributes to slower forest growth and tree damage at high elevations. In addition, chemical pollutants such as pesticides and herbicides leach into soils and watersheds. Some fish species, such as salmonids, require small freshwater streams to spawn. Polluted streams result in the abandonment of traditional spawning areas and ultimately in the loss of salmon populations. Species’ sensitivity to pollution is variable. However, many species are vulnerable to the indirect effects of pollution through the concentration of toxic chemicals in top predators of food chains and disruption of predator-prey interactions.

Global Climate Change

Carbon dioxide released from burning fossil fuels and biomass, deforestation, and agricultural practices contributes to greenhouse gases, which prevent heat from escaping the earth’s surface. With the increase in temperature expected from increasing greenhouse gases, there will be higher levels of air pollution, greater variability in weather patterns, and changes in the distribution of vegetation in the landscape. Some species will not be able to adapt to these changes in the environment and will become extinct. However, it is expected that many plant and animal species will attempt to disperse to higher latitudes and altitudes as the temperature increases. Therefore, any barriers in the landscape, such as highways and urban areas that prevent movement to more hospitable environments, will result in loss of biodiversity.

Corridors and Connectivity

Such threats to biodiversity may cause the extinction of many species. Maintaining the connectivity of the landscape could offset their impacts on biodiversity. The corridor concept proposes that refuges connected by corridors will have higher immigration rates than isolated patches of natural habitat. This can offset extinction by promoting gene flow and preventing inbreeding. Corridors composed of naturally occurring or restored strips of land that connect large habitat patches may facilitate the movement of species between patches, and decrease the effects of threats to biodiversity. Habitat patches connected by corridors must always be large enough to maintain populations of species, especially for large-bodied vertebrates.

The effectiveness of wildlife corridors depends on many corridor design parameters, which include habitat type and structural stage, length and width, and level of human activity in and around the corridor. Individual species require different scales of connectivity. Some species are able to disperse in very narrow strips of natural vegetation, such as hedgerows, whereas other species require large habitat patches close together with very short migration distances through unsuitable habitat. Solely retaining or enhancing narrow strips of vegetation between habitat refuges cannot maintain biodiversity; the habitat values of the overall landscape must be retained.

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