gre考试阅读真题解析(B)_GRE阅读

gre考试阅读真题解析(B)

　　Other problems can be foreseen. Policymakers need to consider many factors and opinions such as the cost of control compared to existing methods, and the impact of the clearance of bracken on the landscape, wildlife, and vegetation. In fact, scientists already have much of the information needed to assess the impact of biological control of bracken, but it is spread among many individuals, organizations, and government bodies. The potential gains for the environment are likely to outweigh the losses because few plants, insects, mammals, and birds live associated only with bracken, and many would benefit from a return of other vegetation or from a more diverse mosaic of habitats. But legal consequences of attempts at biological control present a potential minefield. For example, many rural tenants still have the right of estoyers, the right to cut bracken as bedding for livestock and uses. What would happen if they were deprived of these rights? Once a biological control agent is released, it is difficult to control its speed. What consideration is due landowners who do not want to control bracken? According to law, the release of the biological control agents must be authorized by the secretary of state 国务卿) for the environment. But Britain lacks the legal and administrative machinery to assemble evidence for and against release.