What’s the conversation mainly about?

M: I just learned from the TV that human beings had used up one third of the world’s resources in the last 30 years. At that rate, how long do you think it will take us before we use up the rest?
W: Let me guess--- . er, about 60 years?
M: You’re close. One estimate gives us 50 years before we will need another planet to sustain the world’s population if it keeps using resources the way it does today.
W: Really? What a terrible thing! I remember our geography teacher told us [8A] people in countries such as America, Japan, and European countries can use up to 30 times the amount of resources as people from poor countries. Human beings simply catch too many fish, use too much wood and waste too much fresh water.
M: Well, she did say that. Do you have any idea as to what percentage of the world’s important fish stocks are already over-exploited?
W: What do you mean by over-exploited?
M: I mean that, at the current rate of use, their species will disappear altogether within the next 10-20 years.
W: Hmmm. I’d say, 50%.
M: [9C] Actually, more, at least 70%. As if that weren’t enough, the commercial bush meat trade takes many rare wild species for luxury food. Are you familiar with this term "bush meat"?
W: Does it mean the meat of forest animals such as gorillas, elephants and chimpanzees?
M: Right, I think you heard the term from the news about the growth of wild demand in Africa. [10D] "Bush meat" is usually understood to refer to the meat, used for food, of any wild animal on Land. Besides, consumption of fresh water has tripled since 1950, and it is becoming a very scarce resource.
W: That’s terrible! We must put brakes on this kind of runaway exploitation of the resources.
M: Well, that’s it.