Biological diversity, very simply, refers to all of the different kinds of life on Earth. Also called biodiversity, biological diversity is often used to refer to the total number of different species on Earth. A collection of this biodiversity would include human beings, Bengal tigers, sugar maples, oyster mushrooms, bacteria and the millions of other living organisms found on Earth. Conservative estimates of the number of species on Earth range from 5 to 7 million but some scientists estimate as many as 30 million! With only about 1.6 to 2 million of these species having been studied (many only at the most basic level) and given a name, much still needs to be learned about the diversity of life on Earth.
Within each species there can also be a high level of diversity. For example, human beings have 100,000 genes of which 10,000 can vary from individual to individual. Variations in these 10,000 genes result in differences, such as race, height, eye color, etc. that make each person an individual.
Although the number of variable genes differ between organisms, many plant species can also show a great degree of variability within a species. For example, plant breeders may screen thousands of wheat plants to find just one individual with the proper mix of genes that can provide resistance to rust, a common wheat disease. When differences within a species are combined with differences between species an idea of the magnitude of the Earth's biological diversity emerges. It should give us pause to reflect upon what we lose when a species goes extinct or the population of a species is drastically reduced.
Much of the Earth's bio-diversity is concentrated in the tropics. Some scientists estimate that 50 percent of all species on the planet are found in tropical rain forests that comprise only 6 to 7 percent of the Earth's land surface. Given the rapid rate at which tropical rain forests are being cut, it is estimated that up to 20 percent of the Earth's biodiversity may become extinct in our lifetime! Loss of this biodiversity means we would not only lose rich and beautiful ecosystems but we might also lose plants and other organisms that could improve or enrich our lives. Already the tropical forests have provided humankind with food crops we enjoy daily, such as, tomatoes, peppers, corn, rice, coconut, banana, coffee, cocoa, cassava (tapioca), beans and sweet potatoes, to name but a few. Tropical biodiversity has also provided us with many pharmaceuticals, such as quinine for treating malaria and vincristine and vinblastine which are used to cure childhood leukemia. How many more valuable products lie waiting in the tropical forests to be discovered before they disappear?