Government activities may have damaged environmental impacts. A whole range of policies, from farm- price support to protection for coal-mining, do environmental damage and often make no economic sense. For example, more intensive farming tends to worsen soil erosion, which threatens the productivity of land in both rich and poor countries. The United States, where the most careful measurements have been done, discovered in 1982 that about one-fifth of its farmland was losing topsoil at a rate likely .to diminish the soil' s productivity. Government policies have frequently added to the environmental damage that farming can cause. In the rich countries, subsidies for growing crops and price supports for farm output drive up the price of land. To in- crease the output of crops per acre, a farmer's easiest option is to use more of the most readily available in- puts: fertilizers and pesticides. Fertilizer use doubled in Denmark in the periond 1960-1985 and increased in the Netherlands by 150 percent. In the late 1980s and early 1990s some efforts were made to reduce farm subsidies. The most dramatic ex- ample was that of New Zealand, which scrapped most farm support in 1984. The end of fertilizer subsidies had been followed by a fall in fertilizer use, and it also stopped land-clearing and over-stocking, which in the past had been the principal causes of erosion. Farms began to diversify. The one kind of subsidy whose removal appeared to have been bad for the environment was the subsidy to manage soil erosion. In less enlightened countries, and in the European Union, the trend has been to reduce rather than eliminate subsidies, and to introduce new. payments to encourage farmers to treat their land in environmentally friendlier ways. It may sound strange but such payments need to be higher than the existing incentives for farmers to grow food crops. Farmers, however, dislike being paid to do nothing. In several countries, they have become interested in the possibility of using fuel produced from crop residues either as a replacement for petrol or as fuel for power stations. Such fuels produce far less carbon dioxide than coal or oil, and absorb carbon dioxide as they grow. They are therefore less likely to contribute to the greenhouse effect. But they are rarely competitive with fossil fuels unless subsidized—and growing them does no environmental harm than other crops. Governmental interference often has an effect that is______.