单项选择题

Everyone knows that the world has too many people. But how many people are too many By what standard is the Earth overpopulated Certainly not in terms of living space. The world’s entire population could fit into Jacksonville, Florida, in the USA, with everyone having standing room. Dense cities often are surrounded by nearly empty countryside. For overpopulation to be real, there must be conditions that are undesirable and unmistakably caused by the presence of a certain number of people. If such indications cannot be found, we are entitled to dismiss the claim of overpopulation.
In arguing their case, believers in overpopulation make references to a vague standard known as "carrying capacity", colorfully illustrated with stories about bacteria and herds of zebras (anything but human beings). Famine, deepening poverty, disease, environmental degradation and resource depletion. Yet on no account is there evidence to support the claim of overpopulation.
In fact, during the 20th century there has been no famine that has not been caused by wars, irrational economic policies or natural disasters. Food is abundant and is becoming cheaper and more plentiful. That good news is due largely to technological advances (the "green revolution") that have provided better seeds, fertilizers, pesticides and methods of farming. The only obstacles to agricultural progress are those created by governments. Imagine what the world would be like today if the fertile farmland of India or Russia had been in productive private hands operating in free markets for the past several decades. Since permitting market incentives in agriculture, India has become a net food exporter and China has experienced a boom in agricultural production.
Catastrophists argue that the bright past does not imply a bright future; they assert that mankind has crossed some fateful threshold. Those who annually predict imminent famine seize on any change as evidence that man’s alleged strain on the environment is finally beginning to show. Thus, if the price of seafood rises, they announce that the seas are nearing exhaustion. They never consider the more plausible possibilities, such as the shift in diet from meat to fish, the decline of the Russian industry during the political break-up of the Soviet Union, or the lack of property rights in the world’s oceans and lakes.
In paragraph 1, the writer suggests that the world’s population