Provided for Non-commercial Research and Educational Use. Not for Reproduction, Distribution or Commercial Use

is not a guarantor of lessened risk; diverse, multiple-species stands themselves are not immune to devastating attack by introduced pests, a situation likely to increase in frequency as a result of globalization of trade in timber products. Often the practices associated with intensive management are the causes of insect and disease problems. For example, the desire to maximize wood production may set the level of tolerable damage from native pests lower than the stable equilibrium levels for the pest; attempts to control the pest at lower levels may cause unstable population growth cycles. The potential risks of plantations stem from their uniformity: the same or a few species, planted closely together, on the same site, over large areas. Pests and pathogens adapted to the dominant species may build up quickly due to food supply and abundant sites for breeding or infection. Proximity of the branches and stems in closely spaced stands may favor buildup of species with low dispersal rates or small effective spread distances. Conversely, the same uniformity of plantations that contributed to the risks of insects and diseases also confers some advantages. Species can be chosen that have resistance to diseases, for example, the greater resistance of loblolly pine (Pinus taeda) compared to slash pine (P. elliottii) to Cronartium rust was one reason loblolly was favored by forest industry in the US South. The shorter rotation length of plantations relative to naturally regenerated stands means trees are fallen before they become overmature and become infected. The compact shape and uniform conditions in plantations facilitate detection and treatment of economically important pests and pathogens. Plantations may negatively impact adjacent communities – because of invasive natural regeneration of planted trees in adjacent habitat or alteration of local and regional hydrologic cycles and poor management practices may damage aquatic systems. Plantations are certainly simpler and more uniform than naturally regenerated stands or native grasslands, and may support a less diverse flora and fauna. Nevertheless, plantations can contribute to biodiversity conservation at the landscape level by adding structural complexity to otherwise simple grasslands or agricultural landscapes and by fostering the dispersal of forest-dwelling species across these areas. Further, comparisons of plantations to unmanaged native forests or even naturally regenerated secondary forests are not necessarily the most appropriate comparisons to make. Although the conversion of old-growth forests, native grasslands, or some other natural ecosystem to forest plantations rarely will be desirable from a biodiversity point of view, in that forest plantations often replace other land uses including degraded lands and abandoned agricultural areas. Objective assessments of the potential or actual impacts of forest plantations on biological diversity at different temporal and spatial scales require appropriate reference points. Forest plantations can have either positive or negative impacts on biodiversity at the tree, stand, or landscape level depending on the ecological context in which they found. Impacts on water quantity and quality can be minimized if sustainable practices are followed; similarly with soil resources and long-term site productivity. Both complex plantations for wood production and environmental plantations can beneficially impact local and regional environments. Lastly, managing forest plantations to produce goods such as timber while at the same time enhancing ecological services such as biodiversity involves tradeoffs; this can be made only with a clear understanding of the Author's personal copy 1680 Population Dynamics | Forestry Management ecological context of plantations in the broader landscape. Tradeoffs also require agreement among stakeholders on the desired balance of goods and ecological services from plantations. Thus, there is no single or simple answer to the question of whether forest plantations are ‘good’ or ‘bad’ for the environment. See also: Boreal Forest; Temperate Forest; Tropical