As major forests decrease in size, carbon and greenhouse gases have increased in the atmosphere. But you can help slow that trend.
"Think about greenhouse gas emissions -- driving less, buy a more fuel efficient car," Sizer says. He also recommends adjusting your thermostats by just a couple of degrees. "It makes a huge difference and saves money as well."
You can also buy carbon offsets. "If you have to fly for work often -- you can buy these offsets by making a small contribution to an organization that is planting trees, sucking up carbon that's being emitted when you fly. These things really add up."
About 20% of the Amazon has already been destroyed, and that's what scares Sizer. "The newest science now says if we deforest, if there's a clearing of more than about 30% to 40% of the Amazon rainforest, it will start to dry out. We'll pass an irreversible tipping point."