The role of governments in environmental management is difficult but inescapable. Sometime

s, the state tries to manage the resources it owns, and does so badly. Often, (21) , governments act in an even more harmful way. They actually subsidize the exploitation and (22) of natural resources. A whole (23) of policies, from farm-price support to protection for coal-mining, do environmental damage and (often) (24) no economic sense. Scrapping them offers a two-fold (25) : a cleaner environment and a more efficient economy. Growth and environmentalism can actually go hand in hand, if politicians have the courage to (26) the vested interest that subsidies create.

No activity affects more of the earth's surface than farming. It shapes a third of the planet's land area, not (27) Antarctica, and the proportion is rising. World food output per head has risen by 4 per cent between the 1970s and 1980s mainly as a result of increases in (28) from land already in (29) , but also because more land has been brought under the plough. Higher yields have been achieved by increased irrigation, better crop breeding, and a (30) in the use of pesticides and chemical fertilizers in the 1970s and 1980s.

All these activities may have (31) environmental impacts. For example, land clearing for agriculture is the largest single (32) of deforestation; chemical fertilizers and pesticides may (33) water supplies; more intensive farming and the abandonment of fallow periods (34) exacerbate soil erosion; and the spread of monoculture and use of high-yielding varieties of crops have been accompanied by the (35) of old varieties of food plants which (36) some insurance against pests or diseases in future. Soil erosion threatens the productivity of land in both rich and poor countries. The United States, (37) the most careful measurements have been done, discovered in 1982 that about one-fifth of its farmland was losing topsoil at a rate (38) to diminish the soil's productivity. The country subsequently (39) a program to convert 11 percent of its cropped land to meadow or forest. Topsoil in India and China is (40) much faster than in America.

A．however

B．therefore

C．but

D．hence