scientists have long been in the business of helping to solve practical societal problems. Leonardo da Vinci helped build machines of war; Lavoisier's talents supplied gunpowder for the American Revolution, and Pasteur's experiments showed brewers and vintners how to keep their beverages from spoiling. Indeed, scientists' skills in practical problemsolving are often a barometer for the methodological sophistication of the theories that they employ. Good methods frequently lead to successful problemsolving. Failure at practical problemsolving often indicates poor scientific methods.

What can we learn about the precision, explanatory power, and empirical adequacy of the methods of community ecology – by examining the instances in which it has been used to solve practical environmental problems? This is the main question we assess in these ten chapters. Our answer is, in part, that when we wish to apply ecology in order to promote conservation or preservation, our knowledge of particular taxa is more important than our knowledge of general theory. In other words, following Kitcher's (1985b, 1989) distinction, we believe that, for practical problemsolving, “bottom-up” approaches to ecological explanation are likely to be more fruitful than “top-down,” although both are needed. Top-down approaches tend to use an account of theoretical explanation to underwrite talk about fundamental mechanisms and identification of causes in particular cases. Bottom-up approaches tend to focus on specific phenomena; they emphasize our ability to see causal relations in such phenomena and then to pull together results about individual cases or events into some sort of theoretical explanation.