overharvesting the oceans, we have dragnets that could drag the entire ocean. that s how efficient our technology is. food production, we have to worry about, because water, water is the key to food production and there are going to be perhaps water wars in the future. arthel: are you concerned about water wars and concern about running out of water? there will always be water on the earth, the question is what it takes to irrigate, and the kind of commodities start to rise. so because we re at the top of the top chain doesn t mean that we re invulnerable to what s happening outside where bio diversity is threatened. you mentioned insects could overrun the earth. that s in science fiction. but the cockroach, they never seem to go away. we ve got to figure out a way to get rid of them. dr. michio kaku, thank you very much. the new book is physics of the future .