Unit 4: Ecological Complexity and Biodiversity in B.C.
Introduction to Unit 4
In this unit we will be listening to a presentation by Dr. Brian Starzomski, of University of Victoria School of Environmental Studies.
Learning Objectives
After successfully completing this introductory unit, you will be able to:
- Understand the unique situation of British Columbia re biodiversity
- Understand the complexity of biodiversity in local and regional ecosystems
Context
Of all the Canadian provinces and territories, British Columbia is home to the richest diversity of vascular plants, mosses, mammals, butterflies and breeding birds, and the largest number of species of reptiles, tiger beetles and amphibians found only in one province or territory. This species richness is exemplified by the complex Biogeoclimatic Zone system, which divides the province into 14 separate BEC zones. A biogeoclimatic zone is defined as “a geographic area having similar patterns of energy flow, vegetation and soils as a result of a broadly homogenous macroclimate.” The BEC zones are further broken down into subzones for relative moisture and temperature levels.
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, alpine plateaus, valleys and coastal plains with their associated lakes, rivers and wetlands to form a myriad of complex and varied ecosystems. Many species of plants and animals are endemic to BC, meaning that they are found nowhere else in the world. Despite this uniqueness, B.C. has more species at risk than any other province and is one of only three provinces that lack stand-alone legislation to protect endangered species.
The situation on southern and eastern Vancouver Island is one of the most unique: here winter rainfall is considerably less and the summer drought longer and hotter (i.e. Mediterranean conditions). The resulting natural forest is a mixture of open savanna with Garry Oak, Arbutus and Douglas-fir trees. This habitat, largely disturbed by two centuries of European colonization, is one of the most endangered ecosystems in Canada. Because so much habitat has been lost or degraded, more than 100 species of plants, mammals, reptiles, birds, butterflies and other insects are officially listed as “at risk” in these ecosystems.
Less than 5% of the original Coastal Douglas-fir and Garry Oak ecosystems remain undisturbed in our local area, stretching from Victoria north to the Comox Valley. Efforts to protect and restore these ecosystems have been ongoing for more than 30 years, however the relentless pressures of land use change, human population increase, arrival of invasive species, and more extreme climatic cycles have made protection and restoration very challenging. The Garry Oak Ecosystem Recovery Team (GOERT) led these protection and restoration efforts for many years; now volunteers and environmental non-profit groups and private landowners have taken up the torch to protect the small amount of Coastal Douglas-fir ecosystem still intact.
Video attribution: “biodiv RestoCourse Starzom2020V2 video” is licensed under CC BY-NC-ND 4.0.
Summary of Key Points
- Scientists distinguish three different types of biodiversity: alpha/beta/gamma;
- Biodiversity extinction on the planet is affecting mainly gamma biodiversity – the number of species on the entire planet
- Many species exist in the world which have not been described, especially insects and bacteria;
- British Columbia holds almost half of the diverse number of species in Canada, due to: landscape diversity; climate diversity; elevation diversity; geology variation; glacial history; and peripheral habitats (northern ranges of habitats).
- The Coastal Douglas-fir Biogeoclimatic Zone is one of the most heavily impacted ecosystem types in the province;
- The main threats to biodiversity are: land use change; climate change; introduced and invasive species; overexploitation of species; and nitrogen deposition.
- All these threats combine as cumulative impacts to change ecosystems.