Animal life hasn’t existed for very long on planet Earth. In the last 500 million years, there have been five mass extinctions, defined as events that wiped out at least 75% of animal life. The Devonian mass extinction is considered to have been caused by the rise of plants on land, which polluted the oceans in the absence of animals.
| Mass extinction | Calculated species loss [1] |
| Ordovician, 439 mya | 84–85% |
| Devonian, 367 mya | 79–83% |
| Permian, 245 mya | 95% |
| Triassic, 208 mya | 79–80% |
| Cretaceous, 65 mya | 70–76% |
We are currently heading for a sixth mass extinction. At current rates, massive ecosystemHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More collapse due to loss of animals is predicted within as few as three of our lifetimes and three-quarters of all species on Earth will be gone within 250–540 years [2].
- Brenchley, P.J., A geologic time scale 1989, by W. B. Harland, R. L. Armstong. A. V. Cox. L. E. Craig, A. G. Smith and D. G. Smith. Cambridge University Press, Cambridge. 1989. No. of pages: 263. Price: £25.00 ($49.50) (hardback, £11.95 ($19.95) (soft cover). ISBN 0 521 38361 7 (hardback). 0 521 38765 5 (soft cover). Geological Journal, 1992. 27(2): p. 199-199.
- Ceballos, G., et al., Accelerated modern human–induced species losses: Entering the sixth mass extinction. Science Advances, 2015. 1(5): p. e1400253.
