, the term 'The Evil Quartet' describes the four major causes of biodiversity loss . These four causes are: (a) Habitat loss and fragmentation, which is the most important cause driving extinction ; (b) Over-exploitation of natural resources by humans ; (c) Alien species invasions, where non-native species cause the decline of indigenous ones ; and (d) Co-extinctions, where the loss of one species leads to the extinction of another associated with it . Because 'The Evil Quartet' comprises all four factors, any comprehensive answer would include all these components.