He means like if all the bees suddenly died out and they weren't there a lot of plants wouldn't be producing their fruit/seeds, mostly the parts of them that we eat. And it would hit us twice because it would also affect the animals we use for food too. While something like that isn't going to kill us off, a very large percent of our population would likely die from starvation.
[LNet]-GSIV:Lysistrata: "And I'm pretty perfect sooooo... What can I say. I'm dedicated. (To Jeril's cock.)"
It's not necessarily the disruption to the food chain itself from a temperature change of only a few degrees--warmer temperatures reduce crop yields quickly, which in turn affects meat prices as grain-fed animals become much more expensive. Major increases in the price of food won't necessarily cripple America, but have the potential to cause devastating mass starvation in the third world.
http://www.economist.com/node/18386161
http://phys.org/news/2013-02-climate...orn-crops.html