Cairns, John Jr.2014-01-232014-01-232009http://hdl.handle.net/10919/25024Change has been the Earth s most notable feature for the past 4 billion years. Earth has already passed two ecological tipping points with the acidification of the oceans and the melting glaciers and ice sheets, both caused by anthropogenic carbon dioxide emissions resulting from the combustion of fossil fuels. Unwise energy use has produced unprecedented economic and exponential population growth, both of which have had harmful consequences for the human species as well as other life forms occupying the planet. Humankind has a moral and ethical responsibility to protect the biosphere.en-USIn Copyrightclimate changepopulation growthcarrying capacitySustainabilityArticlehttp://www.johncairns.net/Commentaries/castchanges2.pdf