What is biodiversity?
One textbook definition is that biodiversity AKA biological diversity is all life on earth; the number, variety and variability of all living organisms. In general, biodiversity is described in terms of three categories discussed below: genetic, taxonomic, and ecological. How do we measure biodiversity?
There are several different scientific models for measuring biological diversity but perhaps the simplest and probably the most commonly used measure is species diversity, also called species richness. Species diversity is simply the number of unique species in a given area; and it is based on the taxonomic diversity in that area. Taxonomic Diversity
Taxonomic biodiversity involves the scientific breakdown of organisms into includes kingdoms, phyla, orders, families, genera, species, subspecies and populations. Taxonomic diversity more simply is all the different species that exist on earth, where a species is a unique population of individuals that are genetically dissimilar enough where they cannot produce viable offspring (young that survive and are themselves also able to reproduce). Taxonomic diversity is what most people would think of when they are asked what biological diversity is. Though when most of us think of taxonomic biodiversity we probably think of trees, bears, whales, eagles, etc, it is important to note that by far the greatest biological diversity that exists is that of micro-organisms, most of which have yet to be described or even identified by science. It is equally important to note that there are many other critical elements of biodiversity that should not be ignored. Genetic Diviersity
Genetic biodiversity within a population of the same species involves individuals and their unique combinations of genes and chromosomes, indeed the very fabric of all other aspects of biodiversity. Genetic diversity provides populations with enough variability that they should be able to survive changing environmental conditions because some variants would possess the unique genes that enable them to survive. Without genetic diversity we get the “bottleneck effect” where a population is reduced to few individuals and as a result previously rare or uncommon genes could get multiplied in the new population, this may produce effects that are beneficial in terms of survival but too often it makes the remaining individuals too susceptible to both genetic and environmental diseases as well as changing conditions. Ecological Diversity
Finally ecological diversity looks at the diversity of habitats on which individuals within a species depend on for their own unique niches that they occupy within the ecosystem. For example structural diversity in a forest looks at the vertical or horizontal distribution of plants, looking for instance at those that make up a forest canopy, the trees and shrubs, as well as those that grow on the forest floor, plus the epiphytes which live on the trees themselves, deriving nutrients from the air and small pockets of soil that develop in moss layers far above the forest floor. Functional diversity looks at nutrient cycling, energy flows and trophic-level relationships (the food chains or pyramid). It is often also very important to look at ecological diversity in terms of time because at different seral stages an ecosystem may reach peaks in their species richness in intermediate rather than climax stages, and may in fact reach several peaks in richness before levelling out. Values of Biodiversity
In summary, biodiversity is the sum of all life on earth and the unique environment it exists in. That is what biodiversity is but what does it really mean to us? Most of us will no doubt think of all the uses of biodiversity, our food sources, our textiles and fibres, our clothing and shoes, our paper and paper products, cures for common ailments, cultural values, the list can go on forever describing all the ways that biodiversity is useful to us. But what about the uses not yet discovered? What about the needs that biodiversity can supply that we don't even know exist yet? Even beyond future hypothetical uses for biodiversity (such as a cure for cancer) can we appreciate biodiversity for itself? Biodiversity can be simply measured by species richness but no means of measurement can ever do it justice simply because we still don't know how to value biodiversity. For instance, we can say that a temperate rainforest has higher species richness than a comparable size of land in a baking hot sub-equatorial desert, but which biodiversity is more valuable, can we even say that one is more valuable than the other? And what does this mean for conservation of biological diversity? If we admit that biodiveristy is valuable then are we admitting that life other than human life is equally valuable and has a right to continue living? (ie do we humans have the right to decide which species will survive and which will not). These are important questions we must now consider in a way that we never have before. Most people are not even aware that humanity is currently causing a mass extinction of biological diversity that, by the time its through, will compare to the great mass extinctions in the history of this planet, such as the one that took the dinosaurs. What's more, is that the current extinction is occurring at a faster rate than ever likely experienced before since historically most mass extinctions occurred over periods of thousands of years. If we value biodiversity, as I believe we should, then we should realize that we are on the wrong path and we should do what we can to prevent this catastrophe. See the Nature Stewardship page for more on what you can do for biodiversity. 
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This page was last updated on: February 19, 2007
We do not inherit the earth from our ancestors, we borrow it from our children
In Wilderness is the preservation of the World. - Henry David Thoreau
The frog does not drink up the pond in which it lives. - Chinese Proverb
