Pollution diminishes the value ofour resources and places burdensome costs on farmers and their families and on society as a whole. We can reduce these costs in several ways. We can act against the pollutants themselves, or to change the circumstances under which damaging effects occur, or against the underlying causes of the problem. We can stop pollution altogether, or we can encourage the adoption of alternative agricultural practices that are low polluting. Thus, control of pollution can be targeted against any or all of the components in the chain we described in the introduction to this book (see Figure 1.1). The actions taken are essentially technological, such as installing a treatment plant to remove nitrates from a domestic water supply or introducing a biological agent to control a pest that does away with the need to use pesticides. But whether they are adopted depends on the presence of knowledge, economic incentives and legal regulations. Farmers' practices and behaviour may be changed by the provision of advice and information, or by incentives in the form of prices, taxes, subsidies or by regulations that enforce change. In practice, effective control of pollution inevitably requires a mix of all three approaches and an integration of different disciplines and sectors.