Part 1 explains the concept of mass extinction and presents current population monitoring data illustrating the current 6th mass extinction (endangered species, IUCN red list…).
Part 2 details the 5 factors of biodiversity collapse and the associated human activities and introduces historical perspective.
Part 3 concludes with a discussion of the loss of knowledge and experience of living things, and the phenomenon of ecological amnesia.
The theory of evolution, established in the 19th century and consolidated in the 20th century with advances in genetics, explains the emergence of species, including humans, through genetic differentiation from common ancestors.
It is based on the random modification of hereditary traits via mutations, transmitted from generation to generation, and on natural selection favoring the survival and reproduction of the most advantageous traits.
Biodiversity is always evolving, with new species appearing and others dying out.
The living world is dynamic, with some species naturally becoming extinct and others appearing (background extinction). But when a large number of species become extinct at the same time, we speak of a mass extinction.
The Earth has already experienced five mass extinctions, the best-known being the extinction of the dinosaurs.
Today, a 6th mass extinction of species is considered to have begun, with extinction rates greater than those of previous crises. Unlike previous extinctions, which took place over very long periods (millions of years), this biodiversity crisis is extremely rapid. It is entirely caused by human activities.
Human activities exert numerous pressures on biodiversity:
- land and sea use change (e.g. deforestation), destroying habitats and ecosystems and reducing the territories available to wild species
- overexploitation of natural resources (e.g. fishing, forestry, intensive agriculture…)
- climate change (fossil fuels…)
- pollutions (chemical, plastic, noise, light, etc.)
- displacement of invasive species
All these drivers are leading to the extinction of biodiversity. A quarter of all living species are threatened with extinction by 2050.
Several phenomena are at play.
Ecological amnesia (Pauly): there is a loss of perception of change as each generation redefines what is “normal”. For example, we've forgotten that huge agricultural plains are not “normal” landscapes and didn't exist before the 60s and the Green Revolution. We've forgotten the abundance of fish and cetaceans in our oceans, emptied by intensive whaling in the 19th century and today by industrial fishing.
Ecological amnesia is accentuated by the decline of nature experienceand knowledge in many modern societies (Pyle 1978).
Generally speaking, when the environment changes faster than a species can evolve and adapt, most individuals die or fail to reproduce, and the species declines and becomes extinct. Nature will adapt, but will we be able to?