Introduction of species: alien invasives

The subject of ownership discussed previously is an issue because much reproductive material has been collected in one nation or geographic region, and introduced into another. This has been the case for most agricultural crops, and is also the case for many tree species. Such introduced or exotic species have often been a success because they have been selected from a wider range of species with desirable traits (from a forestry point-of-view - such as fast growth), than would be available from local, native or indigenous species. The introduced species often have no diseases or pests in their new environment and so grow better. Introduced hybrids can show particularly favourable characteristics in this respect.

In the majority of cases, introduced species are frequently of very great economic, environmental and social value and, at times, they help sustain national and local economies; they are thus, per se, acceptable or desirable. However, such species can give cause for concern when insufficient consideration is given to the context of their use and their management. This has led to exotic species getting a bad name, and being rejected for real or perceived environmental and cultural reasons that may or may not be justified (e.g. in the case of prosopis, eucalyptus, some pines and poplars).

The natural reproductive ability of some introduced species is currently giving cause for real concern. Although climatic differences in their new environment may mean that they cannot reproduce at all, in other cases, ease of natural regeneration and lack of pests and diseases result in the species becoming uncontrollable and, at times, weedy. Weediness (or invasiveness) is not only a physical problem, but also a biological one when the species alters a native ecosystem in a direction conceived as undesirable.¿Invasives" and especially ¿alien invasives¿ are presently a political as well as technical issue. They are presenting serious problems in many countries, and require stringent control, usually by eradication or rendering the plant sterile, and banning of import and further propagation. It is possible to be pre-emptive by studying the reproductive biology of the species and its growth characteristics in its natural habitat, and ensuring that proper considerations are given to all aspects, including invasiveness, in species introduction and management. FAO, with a number of partners, has sponsored a number of studies reviewing the issue.

last updated:  Wednesday, April 18, 2007