Because forest restoration is a process, a good restoration programme starts with a fairly clear idea of what type of forest is being created, that is, the target for restoration and the associated activities. This can only be approximate, because ecosystems change and evolve, but can help set the approach and time scale.140 There can be many different aims and end points, for instance:
140 Peterken, 1996.
• Restoration of deforested land with a staged process leading to a more natural forest over time, e.g., as in Guanacaste, Costa Rica, where exotic species are used as nurse crops for natural forest141
• Restoration of forest with specific social values, e.g., tembawang fruit gardens of western Borneo, which are planted for their nontimber forest products but are also high repositories of biodiversity
• Restoration of specific values within managed forests by specific interventions, such as re-creation of dead wood components in southern Swedish and Finnish forests
• Restoration as a centuries-long process, where initial intervention is then augmented by natural changes and aging, as in the previously deforested Agathis forests of northern New Zealand
Although it is often assumed that restoration aims to re-create a "natural" forest, this is not always the case. Many efforts aim instead at culturally important forests, as in parts of the Mediterranean, or even seek to limit the spread of trees to maintain game animals, as in many of the eastern African savannahs. Whatever the aims, good restoration needs to be planned and monitored against some framework, usually a similar forest type that identifies a template for the type of forest being restored.
Reference forests provide a model to follow. The best reference forests are those that have
141 Janzen, 2002.
been identified, protected, and monitored over time, so that they have an associated body of understanding about their ecology. They will often, although not invariably, be old forests, although younger forests can provide valuable reference for successional stages. Even quite newly identified reference forests can provide valuable information if their history is known and it will often be necessary to find a reference forest or reference landscape as part of the planning for forest restoration at a landscape scale. Sometimes reference forests need to be re-created theoretically from historical records and pollen diagrams. Although most valuable in relating to forest types in the same ecosystem, reference forests also provide information of value to forests far away. It is important to understand the relationship between the historical reference forest and the future forest being re-created or modified; the reference forest is not necessarily the same as the target forest being restored. Sometimes it will be possible, over time, for the latter to become very similar to its reference, while in other cases this will be impossible either because of other pressures on and needs from the forest or because conditions have changed and certain elements of the original forest are irrecoverable. A clear understanding of this relationship is important when setting targets for restoration.
Reference landscapes provide information on different aspects of ecology, particularly composition, ecological processes and functioning, and, crucially but often the most difficult to pinpoint, cyclical changes over time. Locating forests undisturbed enough to exhibit natural changes either through a gradual process of aging and renewal or from evidence of natural catastrophic events is now increasingly difficult in many areas, yet an understanding of how forests renew themselves is important in recreating near-to-natural forests and in understanding likely pressures on managed forests.
Other elements to consider in defining targets for restoration include long-term human interaction with forests and the evolution of cultural landscapes (many forests have never existed without the presence of humans so that the idea of a pristine, human-free ecosystem is often little more than a myth). The probability of future climate change and other forms of environmental disturbance means that targets should be tailored with this in mind, also suggesting the limitation of following reference landscapes too closely, when they may be undergoing change themselves. More generally, targets for restoration should be developed with an understanding of likely changes. The idea that vegetation evolves to some climax type and then stays the same is now largely disproved, at least at the level of a particular stand, where flux is expected and is likely to be constant. In the end, choices usually need to be made about levels of biodiversity, naturalness, and livelihood values contained in particular restored forests, and reference forests can only provide information to help with these more political choices.
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