It's Earth Day.
Gaia (proper name) - From Greek creation mythology, Gaia is Mother Earth. From her was born all of creation. She is mother of the sky (Uranus) and of the sea (Pontus). From her womb came the Titans and the Cyclopes.
Gaia Hypothesis - Proposed by scientist James Lovelock in 1965. This hypothesis observes that the Earth is a self-substaining cradle of life - a living being if you will. At its simplest, the waste product of plant life (oxygen) is necessary for animal life to thrive while animal waste (carbon dioxide) is required for photosynthesis. All life lives in balance with all other life.
If this balance is disrupted, say by releasing an excessive amount of carbon dioxide into the atmosphere, the Earth will heat up - killing off animal life while allowing plant life to thrive - until the balance is restored.