Biological diversity or 'biodiversity' refers to the variety of life on earth. 

As defined by the United Nations Convention on Biological Diversity, it includes diversity of ecosystems, species and genes, and the ecological processes that support them. Natural diversity in ecosystems provides essential economic benefits and services to human society - such as food, clothing, shelter, fuel and medicines - as well as ecological, recreational, cultural and aesthetic values, and thus plays an important role in sustainable development. 

Biodiversity is under threat in many areas of the world. Concern about global biodiversity loss has emerged as a prominent and widespread public issue.

2010 has been declared the International year of biodiversity.

The Holocene extinction is the widespread ongoing extinction of species during the current epoch.  However the quantity of recent extinctions is difficult to measure or estimate.  Between 1500 and 2009 there are 875 documented extinctions however the estimate for extinctions in the last century is between 20,000 and 2 million species.