Biodiversity refers to the variety of species found in an ecosystem.
Extinction is when a group of organisms fail to adapt to the environment and therefore cannot survive. This is a natural process.
Fossils show that there have been several mass extinction events. After each, biodiversity has slowly increased as the remaining organisms have adapted to the new environment.
The rate of extinction can be calculated from the presence or absence of higher animals and birds. Normal extinction rates for these animals are compared with current extinction rates.
This calculation is only an estimate and can be used to calculate the presence of little-known organisms. The spread and increase in size of the human population is contributing to the extinction rate.
It is noted that the extinction of mega fauna – giant animals such as woolly mammoths – coincided with the spread of humans.
The destruction of natural habitats by humans is causing the current rate of species extinction to be much higher than the natural background rate.