Biodiversity refers to the variety of life on earth. This life, in all its forms and dimensions, occurs in the context of ecosystems: it depends on, and interacts with, other organisms and the physical environment. Biodiversity represents the collective "knowledge" acquired by evolving species over millions of years, on how to survive in the highly variable environmental conditions that the Earth experiences.
In other words, biodiversity, as shaped by evolution since the appearance of life on Earth over three billion years ago, is an essential component in the functioning of the Earth system. This biodiversity is of course directly linked to the geoclimatic and physico-chemical conditions of the ecosystems in which it thrives. However, as a result of rapid climate change induced by human activity, we are witnessing a veritable collapse in biodiversity on a planetary scale.