Meat reared on land matures relatively quickly, and it takes only a few pounds of plants to produce a pound of meat.

For humans, the Arctic is a harshly inhospitable place, but the conditions there are precisely what polar bears require to survive - and thrive. 'Harsh' to us is 'home' for them. Take away the ice and snow, increase the temperature by even a little, and the realm that makes their lives possible literally melts away.

In terms of personal choices, let's all think more carefully about where we get our protein from.

Sylvia Earle Quotes