We know of more than 1.7 million species, but since most havenít been discovered yet, we can realistically estimate that the actual number is closer to 40 million. Insects alone count for approximately 75% of all species. It is a fact that from a certain length, the number of species is negatively correlated with their size; the smaller they are, the more they multiply.
Every species possesses a combination of genes that defines the characteristics of their morphology and their capacity to interact with the world. The total amount of genes differs; bacteria count 1000, mammals 100 000 and flowering plants possess the highest amount with more then 400 000. This genetic baggage is passed through to each generation and causes a species to evolve in a certain way when confronted with natural selection. Natureís constant pressure: predators, extreme temperature or the challenge to consume energy, explains their different shapes.
Genetic diversity plays a crucial role in the stability of our ecological system, and what we retrieve from it is priceless. Every species fulfills a role in the earthís biosphere and assures ecological survival. By self-regulation, biodiversity keeps the soil fertile, recycles all nutrients and cleans the air and water. Moreover, the richer the genetic baggage, the higher the capacity to fight different virus or bacteria, which are also species that evolve. For every virus, there is a gene capable to neutralize it. It is the diversity of the genetic baggage that makes natural extinction so rare.
Many products, whether they be industrial or medicinal, exist thanks to biodiversity. Because of its rich diversity, the tropical forest provides us with special medicines that can help us overcome diseases. But most importantly, biodiversity provides food for humans. Different kinds of plants and animals mean different kinds of food as well. Food diversification assures us the possibility to have provisions when contamination or extinction happens to a certain type of food. This is a crucial advantage for our survival.
Today, approximately half of all species are found in tropical forests. This is known as megadiversity. These areas are often victims of human expansion and deforestation, which are problems related to overpopulation. It causes an important loss to the gene pool. This phenomenon is known as genetic erosion, which is a decrease of genetic diversity. Since a species often depend on a specific environment or another species to survive (food chain), genetic erosion is a real domino effect. What we have now on our planet is the heritage of a great evolution. However, since human expansion is driving many species to extinction, the genetic reservoir is declining as well.
Basically, biodiversity provides everything humans need to survive: food, fresh air, clean water, clothing, medicine and material for shelter (different types of wood for example). It is considered for some people to be the most precious thing we have on earth. A rich ecological environment is indeed very complex, and is impossible for human to recreate. Genetic erosion is wiping out millions of years of evolution and a loss in biodiversity is not something we can bring back.