Biodiversity Issues
(Michael Pidwirny, Tracy Gow, Jillian Cornock, Jennifer Danzinger, Shaun Davies and Shannon McCallum)

1. INTRODUCTION

We often ignore the importance that plants and animals play in human society. Humans have used these living resources as a source of food, clothing, transportation, labor, and chemicals for industrial products and medicines. The types of species we currently use to better our lives represents only a small proportion of the total number of species currently living on this planet. Many of these species have never been classified by biological taxonomists . If fact, biologists are not completely sure how many different species live on the Earth. Estimates of how many species exist on the Earth range from 2 million to 100 million. To date, about 1.8 million species have been classified, primarily in the areas of the middle latitudes. Most of the unclassified species on this planet are invertebrates. This group of organisms includes insects, spiders, mollusks, sponges, flatworms, starfish, urchins, Earthworms and crustaceans. The cataloging of species in the tropical rainforest has been quite limited. Scientists estimate that this single biome may contain 50 to 90 % of the Earth's biodiversity.

The loss of an entire species is called extinction. The death of all the individuals in the species known as the passenger pigeon a t the turn of this century would be an example of an extinction. The death of a local population of a species is called an extirpation. An example of an extirpation, is the complete decline of grizzly bears from the state of Colorado. In British Columbia, 28 species of vascular plants and 11 species of vertebrates are consider extirpated. Species heading toward extinction can be classified as either endangered or threatened . An endangered species is one having so few individual survivors that the species could soon become extinct over all or most or its natural range, for example:

• White Rhinoceros - 100
• California Condor - Teens
• Giant Panda - 1000
• Florida Panther - 30 to 50

Some endangered species have too few individuals for future survival and are said to be ecologically extinct. Species with too few individuals can die-out if the low numbers results in inbreeding or the inability of population members to find mates. A threatened species is still abundant in its natural range but is declining in numbers and likely to become endangered. In British Columbia, 66 species and sub-species of amphibians, reptiles, birds and mammals are designated as either threatened or endangered.

Many species have gone extinct over time. The primary reason for these extinctions is environmental change or biological competition. Since the beginning of the industrial revolution, a large number of biologically classified species have gone extinct due to the actions of humans. This includes 83 species of mammals, 113 species of birds, 23 species of amphibians and reptiles, 23 species of fish, about 100 species of invertebrates, and over 350 species of plants. Scientists can only estimate the number of unclassified species that have gone extinct. Using various methods of extrapolation, biologists estimate that in 1991 between 4000 to 50,000 unclassified species became extinct, mainly in the tropics, due to our activities. This rate of extinction is some 1,000 to 10,000 times greater than the natural rate of species extinction (2 - 10 species per year) prior to the appearance of human beings. The continued extinction of species on this planet by human activities is one of the greatest environmental problems facing humankind.

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