DENDROLOGY

Detailed explanation-1: -Unlike previous extinction events caused by natural phenomena, the sixth mass extinction is driven by human activity, primarily (though not limited to) the unsustainable use of land, water and energy use, and climate change.

Detailed explanation-2: -Unlike past mass extinctions, the current extinctions are being caused by human activities. Human impacts on biodiversity stem from overhunting and overfishing, habitat loss and degradation, climate change, and the facilitation of species invasions.

Detailed explanation-3: -Harvard biologist E. O. Wilson estimates that 30, 000 species per year (or three species per hour) are being driven to extinction. Compare this to the natural background rate of one extinction per million species per year, and you can see why scientists refer to it as a crisis unparalleled in human history.