By biodiversity we mean the variety of life on Earth and the interaction among its creatures. From a different viewpoint, it may also be defined as the “knowledge” accumulated during the many million years of evolution that makes living organisms capable of adapting to the ever-changing environmental influences. Biodiversity is the greatest in the tropical rainforests near the equator (which host two-thirds of all known species), and decreases over distance to the poles. We may describe it with the number of species present, their incidence and its time and spatial patterns.
Biodiversity is threatened by many factors: apart from natural causes such as ice ages, continental collisions, volcanic eruptions or the destructive power of meteorites, the most consequential one is human activity. The destruction of habitat, environmental pollution, the increasing human population, poaching and the spread of invasive species all contribute to the immense decrease of biodiversity, leading to a possible ecological catastrophe in the future.