2 . Imagine living on the edge of a vast desert, which is moving quietly closer to your village every day and covering your fields. The desert is on the move. This is called desertification (沙漠化).

Desertification occurs in regions close to an already existing desert. It generally arises from two related causes. The first is over-use of water in the area. There is not enough water in any case, and if it is not carefully used, disaster can follow. As time goes on, water shortages make farming more and more difficult. In some places, locals can remember local lakes and marshes which were once the homes for all kinds of fish and birds. They have been completely buried by the sand now. Farmers leave the land, and fields are replaced by deserts.

The second cause is misuse or over-use of the land. This means that the wrong crops are planted, and need more water than is available (可获得的). Ploughing (耕种) large fields and removing bushes and trees means that the wind will blow away the soil. Once the soil is lost, it is hard to replace, and if there is rain, it has nowhere to go, and brings no benefit.

It is not only the farmers and villagers who suffer. Every spring, the skies over some of cities, thousands of kilometers away from the deserts, can be darkened by sandstorms. Dust from deserts can have a great effect on weather systems. While desertification is perhaps being partly caused by global warming, these sandstorms can make global warming worse by adding to what is known as the greenhouse effect.

What can be done to slow down or stop the process of desertification? A great deal of work is already under way. Obviously the first step is to find new water sources. Tree planting can also help, by providing barriers (屏障) between desert and rich field. Some types of grass also hold the soil together, and stop the wind taking it. Without these efforts, it will be harder and harder to stop the world’s deserts in their tracks, and more and more farmers will give up and head for cities. The lesson to be learnt lies beneath (在……下面) the sand.

5 . Global warming may or may not be the great environmental crisis of the 21st century, but — regardless of whether it is or isn’t — we won’t do much about it. We will argue over it and may even, as a nation, make some fairly firm commitments (承诺) to avoid it. But the more dramatic and meaningful these commitments seem, the less likely they are to be observed.

Al Gore calls global warming an “inconvenient truth,” as if merely recognizing it could put us on a path to a solution. But the real truth is that we don’t know enough to relieve global warming, and — without major technological breakthroughs — we can’t do much about it.

From 2003 to 2050, the world’s population is estimated to grow from 6.4 billion to 9.1 billion, a 42% increase. If energy use per person and technology remain the same, total energy use and greenhouse gas emissions (mainly, CO₂) will be 42% higher in 2050. But that’s too low, because societies that grow richer use more energy. We need economic growth unless we condemn (注定) the world’s poor people to their present poverty and freeze everyone else’s living standards. With modest economic growth, energy use and greenhouse emissions will more than double by 2050.

No government will adopt strict limitations on economic growth and personal freedom (e.g. electricity usage, driving and travel) that might cut back global warming. Still, politicians want to show they’re “doing something”. Consider the Kyoto Protocol (京都议定书). It allowed countries that joined to punish those that didn’t. But it hasn’t reduced CO₂ emissions (up about 25% since 1990), and many signatories (签字国) didn’t adopt tough enough policies to hit their 2008-2012 targets.

The practical conclusion is that if global warming is a potential disaster, the only solution is new technology. Only a determined research and development program might find ways of breaking our dependence on fossil fuels or dealing with it.

The trouble with the global warming debate is that it has become a moral problem when it’s really an engineering one. The inconvenient truth is that if we don’t solve the engineering problem, we’re helpless.

In order to save this species from     1    , the Chinese government placed it under national protection. Zhaxi and other     2     watched over the antelopes day and night to keep them safe from     3    . Bridges and gates were     4     to let the antelopes move easily and keep them safe from cars and trains. The measures were     5    .

Yours,

Li Hua