Acclimatisation societies were voluntary associations, founded in the 19th and 20th centuries, that encouraged the introduction of non-native species in various places around the world, in the hope that they would acclimatise and adapt to their new environments. The societies formed during the colonial era, when Europeans began to settle in numbers in unfamiliar locations. One motivation for the activities of the acclimatisation societies was that introducing new species of plants and animals (mainly from Europe) would enrich the flora and fauna of target regions. The movement also sought to establish plants and animals that were familiar to Europeans, while also bringing exotic and useful foreign plants and animals to centres of European settlement.
It is now widely understood that introducing species to foreign environments is often harmful to native species and to their ecosystems. For example, in Australia the environment was seriously harmed by overgrazing by rabbits. In North America house sparrows displaced and killed native birds. In New Zealand, introduced mammals such as possums and cats became threats to indigenous plants, birds and lizards. Around the world, salamander populations are threatened by introduced fungal infections. Consequently, the deliberate introduction of new species is now illegal in some countries.[1]
Alfred Russel Wallace attempted to define acclimatisation in his contribution on the subject in the Encyclopædia Britannica, 11th edition (1911). Wallace tried to differentiate the concept from other terms, such as "domestication" and "naturalisation". He noted that a domesticated animal could live in environments controlled by humans. Naturalisation, he suggested, included the process of acclimatisation, which involved "gradual adjustment". The idea, at least in France, was associated with Lamarckism, and Wallace noted that some, such as Charles Darwin, denied the possibility of forcing individual animals to adjust. However, Wallace pointed out that there was the possibility that there were variations among individuals and so some could have the ability to adapt to new environments.[2]