填空题
A very important world problem, if not the most serious of all the great world problems which affect us at the moment, is the increasing number of people who actually inhabit this planet. The limited amount of land and land resources will soon be unable to support the huge population if it continues to grow at the present rate.
In an early survey conducted in 1888, a billion and a half inhabited the earth. Now, the population exceeds five billion and growing fast--by the staggering figure of 90 million in 1988 alone. This means that the world must accommodate a new population roughly equal to that of the United States and Canada every three years! Even though the rate of growth has begun to slow down, most experts believe the population size will still pass eight billion during the next 50 years.
If we examine the amount of land available for this ever-increasing population, we begin to see the problem. If everyone on the planet had an equal share of land, we would each have about 50,000 square meters. This figure seems to be quite encouraging until we examine the type of land we would have. Not all land is useful to humans as it cannot produce food. We can cut out about one fifth of it because it is permanently covered by mow and ice. Then we can cut out another fifth because it is desert. Another fifth is too mountainous or is too great a height above sea level. A tenth doesn’t have enough soil for crops to grow--it is hard rock. Now the position begins to look rather more bleak!
Obviously, with so little land to support us, we should be taking great care not to reduce it further. But are we Mankind seems to be unable to accept that we live on a finite planet--we act as if its resources were infinite. Because of overpopulation and over-consumption, humanity is incapable of supporting itself on its ’income’—the energy arriving continuously from the son. Instead, we are consuming its ”capital’--its nonrenewable fossil fuels and other mineral deposits that took millions of year to form but which are now being destroyed In decades. We are also doing the same with other vital resources not usually thought of as being nonrenewable such as fertile soils, groundwater and the millions of other species that share earth with us.
Man is constantly destroying the very resources which keep him alive. He is destroying the balance of nature which regulates climate and the atmosphere, produces and maintains healthy soils, provides food from the seas, etc. In short, by only considering our needs of today, we are ensuring there will be no tomorrow.
In short then, it is everybody’s duty to safeguard the future of the mankind--not only through population control, but by being more aware of the effect his actions have on nature. Nature is both fragile and powerful. It is very easily destroyed; on the other hand, it can so easily destroy its most aggressive enemy--man.