The ‘Evil Quartet’ refers to four main causes of species extinction, as identified by Michael Soulé:

.Habitat loss – Destruction of natural habitats.

.Over-exploitation / co-exploitation – Unsustainable use of species.

.Alien species invasion – Introduction of exotic species.

.Co-extinctions – Extinction of one species leading to extinction of others dependent on it.

Hunting is included under over-exploitation, so it is not counted separately in the “Evil Quartet

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