Biodiversity is simply the variety of living things-or number of species-in a particular area. It is a contraction of the words "biological" and "diversity". Biodiversity can refer to variation within or between species, but is usually used to refer to the variety of life in an ecosystem.
There are about 5 to 30 million different species on Earth, with about 1.75 million being named, classified, and described. Most of those that have been named, classified, and described are insects, meaning, as the count now stands, terrestrial ecosystems are more biodiverse than ocean ecosystems.
Biodiversity is fundamentally important to the functioning of natural and man-made ecosystems. All species play a role in the services that ecosystems provide. They cycle the matter and forward the energy that all of us depend on.
But biodiversity is taking a hit from human activity. Globally, it is declining at rates estimated to be 100 to 10,000 times faster than natural. The main reason? We are destroying the habitat on which these species depend-we are destroying their homes. Another scary estimate? Up to 50% of well-understood species are threatened with extinction.
Some scientists argue that we are in the middle of the Earth's 6th mass extinction event. Go us.