Eucalyptus beyond Its Native Range: Environmental Issues in Exotic Bioenergy Plantations

The genus Eucalyptus is native to Australia and Indonesia but has been widely planted in many countries. Eucalyptus has proven to be particularly successful in tropical and subtropical regions. Several species are also successful in some temperate regions, but problems with sudden and severe frosts pose limitations. Current plantations around the world are dominated by the “big nine” species (E. camaldulensis, E. grandis, E. tereticornis, E. globulus, E. nitens, E. urophylla, E. saligna, E. dunnii, and E. pellita) and their hybrids, which together account for more than 90% of Eucalyptus planted forests. Much of current tree improvement efforts focus on the use of hybrids and clones, and development of genetically modified Eucalyptus is already underway. For many reasons, there is increased interest in using wood for energy, and short-rotation plantings of Eucalyptus will likely be an important source of feedstock [1]. Many Eucalyptus species have desirable properties for bioenergy plantations, including rapid growth rates and high wood density. The indeterminant growth pattern and evergreen foliage allow eucalypts to grow whenever climatic conditions are suitable.The sclerophyllous leaves of eucalypts allow them to withstand very dry conditions and may also be an adaptation to low nutrient conditions. However, the same traits that make Eucalyptus attractive for bioenergy and other bioproducts, such as rapid growth, high fecundity, and tolerance of a wide range of climatic and soil conditions, also make them potentially invasive. The prospect of widespread planting of these nonnative species for commercial purposes in the southern United States has again arisen, prompting questions about potential environmental effects. In response, a conference was held in Charleston, South Carolina, in February of 2012 to review the history of Eucalyptus research and culture in the USA and around the world and to examine potential environmental issues surrounding their expanded introduction in the southern USA. Environmental issues addressed included invasiveness potential, fire risk, water use, and sustainability. Papers from that conference, as well as contributions from other countries that shed light on these issues, are the subject of this special issue.