The priorities in conservation should be to reduce extinction rates and to prevent further damage to ‘high-quality’ sites (Chapter 3). However, some sites which have already been damaged still retain valuable features and threatened species. There is increasing interest in attempting to rebuild such communities to a state more like the natural community. These efforts may prove to be particularly valuable when used to enlarge small fragments of habitat. Restoration has been defined by E. B. Welch and G. D. Cooke as ‘any active attempt to return an ecosystem to an earlier condition following degradation resulting from any kind of disturbance’. This includes a return to desirable semi-natural conditions. Several management principles relevant to restoration can be found in Chapters 5 and 7, although those chapters focus more on protection of existing interest and on maintenance of the interest once it has been restored.

Restoration has a long history in conservation. For example, some reforestation of Trinidad and Tobago was undertaken in the eighteenth century, using exotic bamboo to protect soils from erosion. In the English Lake District in the early 1800s, the poet Wordsworth appealed for the release of lakeside back to nature, and advised the planting of native tree species to restore attractive forests. Aldo Leopold was amongst the first ecologists to attempt restoration. From 1934 he worked in an old pasture in Wisconsin, USA, aiming to create and study an imitation of the local tallgrass prairie.