Desertification, the process by which fertile (肥沃的) land becomes desert, has severe impacts on food production and is worsened by climate change.【小题1】

Africa’s Great Green Wall is a project to build an 8,000- kilometre-long forest across 11 of the continent s countries. The project is meant to contain the growing Sahara Desert and fight climate change.【小题2】They include limited political support, lack of money, weak organizational structures, and not enough consideration for the environment. Just 4 million hectares (公顷) of land have been turned into forest since work on the Green Wall began 15 years ago.【小题3】

First proposed in 2005, the project aims to plant a forest from Senegal on the Atlantic Ocean in western Africa to Eritrea, Ethiopia and Djibouti in the east.【小题4】 It could also reduce levels of climate-related migration in the area and capture hundreds of millions of tons of carbon dioxide from the air. Several countries have struggled to keep up with the demands of the project.

【小题5】 Eritrea, Ethiopia, and Sudan have all expanded their efforts. Ethiopia is producing 5.5 billion seedlings leading to thousands of hectares of restored land. Efforts in Eritrea and Sudan have also resulted in nearly 140,000 hectares of newly planted forest. The U. N. desertification agency says the project will need to plant an average of 8.2 million hectares yearly to reach its goal of 100 million hectares by 2030．

Organic foods are produced according to certain production standards, meaning they are grown without the use of conventional pesticides, or chemical fertilizers and that they were processed without food additives. Livestock are raised without the routine use of antibiotics or growth hormones. In most countries, organic produced foods must not be genetically modified. They may also be required to be produced using energy-saving technologies and packaged using recyclable materials when possible.

Early consumers interested in organic food would look for non-chemically treated, fresh or minimally processed food. They mostly had to buy directly from growers: “Know your farmer, know your food” was the motto. Personal definitions of what constituted “organic” were developed through firsthand experience: by talking to farmers, seeing farm conditions, and farming activities. Historically, organic farms were relatively small family run farms—which is why organic food was once only available in small stores or farmers’ markets. However, since the early 1990s organic food has had growth rates of around 20% a year. As of April 2008, organic food accounts for 12% of food sales worldwide. Currently organic food production is legally regulated. Many countries require producers to obtain organic certification in order to mark food as organic.

Several studies have attempted to examine and compare conventional and organic systems of farming. The general consensus is that, in the short term, organic farming is less damaging for the following reasons:

●Organic farms do not release synthetic pesticides into the environment—some of which have the potential to harm soil, water and local wildlife.

●Organic farms are better than conventional farms at sustaining diverse ecosystems, i.e., populations of plants and insects, as well as animals.

●Organic farms are more energy efficient and produce less waste.

Another report published in March 2008 by The Organic Centre claims that organic food is on average 25% more nutritious than conventional food.

However, many critics believe that the increased land needed to farm organic food could potentially destroy the rainforests and wipe out many ecosystems. And organic products cost 10 to 40% more than similar conventionally produced products. Processed organic foods in supermarkets are 65% more expensive.

In 1960 the Aral Sea was one of the world’s largest inland water bodies, covering an area of approximately 68,000 square kilometers (26,000 square miles). By the year 2000 the area covered by the Aral Sea had become less than half its 1960 size, its volume reduced by 80 percent. By about 2010 all that will remain will be three shallow remnants.

What caused the Aral Sea to evaporate over the past 40 years? As recently as 1965, the Aral Sea received about 50 cubic kilometers (12 cubic miles) of fresh water per year. By the early 1980s this number had declined to nearly zero. The reason was that the waters of the Amu Darya and Syr Darya had been diverted to supply a major expansion of irrigated agriculture in this dry realm.

The intensive irrigation has greatly increased agricultural productivity, but not without significant costs. The deltas of the two major rivers have lost their wetlands, and wildlife has disappeared. The once thriving fishing industry has been eliminated, and the 24 species of fish that once inhabited the Aral Sea are no longer there. The shoreline is now tens of kilometers from the towns that were once fishing centers.

The shrinking sea has exposed millions of acres of former seabed to sun and wind. The surface is covered with salt and agrochemicals brought by the rivers. Strong winds routinely pick up thousands of tons of newly exposed materials every year and deposit them throughout the region. This process has not only contributed to a significant reduction in air quality for the region’s population, but has also appreciably reduced crop yields due to the deposits of salt-rich sediments on farmable land.

The shrinking Aral Sea has had a noticeable impact on climate. Without the moderating effect of a large water body, there are greater extremes of temperature, a shorter growing season, and reduced local precipitation. These changes have caused many farms to switch from growing cotton to growing rice, which demands even more diverted water.