Biodiversity And Conservation

The major causes of biodiversity loss are collectively called the Evil Quartet, and they are habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions. Of these, habitat loss and fragmentation is considered the single most important cause driving plants and animals towards extinction, the prime example being the destruction of tropical rainforests such as the Amazon. Co-extinctions are incorrect as the leading cause because they occur secondarily when a species goes extinct and the plants or animals obligately associated with it also disappear. Over-exploitation, such as overharvesting and overfishing, is a significant but not the foremost cause. Alien species invasions cause declines when introduced organisms turn invasive and outcompete or prey on natives, but again this is not ranked first. As described in NCERT Class 12, Chapter 15 (Biodiversity and Conservation), habitat loss and fragmentation is the most important driver because it directly removes the living space that organisms depend upon. Plausibility check: since destroying a habitat eliminates every species living there at once, its primacy among the quartet is internally consistent.