Abstract

Philip E. Hulme recently suggested in TREE that botanic gardens had in the past, and continue to have today, an important role in plant invasions across the globe [1xAddressing the threat to biodiversity from botanic gardens. Hulme, P.E. Trends Ecol. Evol. 2011; 26: 168–174Abstract | Full Text | Full Text PDF | PubMed | Scopus (67)See all References][1]. Although we agree that mistakes might have been made by gardens in the past, we contend that such historical plant invasions need to be viewed in the context of the time, and that the situation is different today.Hulme identifies several invasive plant species for which botanic gardens are inferred as sources for their introduction and early dissemination during the 19th and early 20th centuries. At this time, however, the active introduction and release of plants around the world was being vigorously encouraged and was the mission of many gardens (as well as a host of other agricultural agencies). Although most plant introductions have had a positive result, some of the introduced species have shown invasive potential in some regions. However, we do not believe that it is useful to continue to blame the botanic gardens of today for previous mistakes. Indeed, because of their education missions and scientific expertise, botanic gardens today are taking an active role in combating invasives.The combined collections of the botanic gardens of the world include up to one-third of all known plant species [2xSee all References][2] and although these do include potentially invasive species, these collections also have a considerable conservation value. According to the International Union for the Conservation of Nature, the number of extinct plant species would be 34% higher were it not for those preserved in gardens [3xIUCN Red List of Threatened Species, Version 2010.4. IUCN. See all References][3]. Moreover, no species is invasive everywhere; just because a garden has a species in its collection does not mean that it is introducing or promoting a species that is locally invasive. There are sometimes good reasons to include a regional invasive in a garden's collection; for example, if the species is part of a specialised taxonomic collection, or if it is being used in educational programmes. Telling people not to plant particular species means little: visitors might not recognise a name, but seeing the plant, with interpretation, might help them identify it as something they have in their garden or in their neighbourhood.There is clearly a value to having botanic gardens with wide and extensive collections, but there is also no room for complacency. This is particularly the case in remoter areas, where the lack of economic activity means that there are generally fewer other opportunities for non-native species to be introduced. Ecotourism is often an early activity in remote areas, including the desire to establish a garden. This can lead to increasing anthropogenic disturbance, opening opportunities for invasive species. Such gardens should therefore focus their efforts on the conservation and display of native species, and many are already doing so.Hulme notes that only ten out of 461 botanic gardens in the USA have endorsed the ‘St Louis Declaration’ and its voluntary Codes of Conduct for alien invasive species (http://www.centerforplantconservation.org/invasives/home.asp). Although it might be true that few gardens have completed formal endorsement, we know that 19 Center for Plant Conservation institutions that are not yet endorsers are nevertheless actively engaged in controlling invasive species at 269 sites across the USA. A positive outcome from the St Louis Declaration is PlantRight in California (http://www.plantright.org), fostering partnerships between gardens, nurseries and much of the entire horticulture value chain. The initiative has resulted in the identification of key invasive species from horticulture throughout California, the finding of safe alternatives and now the potential introduction of invasive-free certification for nurseries.In Europe, the European Botanic Gardens Consortium has established an alien plants initiative to identify emerging problem taxa from within the large and diverse botanic collections in European gardens, to alert collection holders to their potential risk of invasiveness. This initiative, which is especially important in an era of climatic change, fosters vigilance through sharing early recognition of these newly or potentially problematic taxa and ensures responsible, pro-active policies across Europe.In concluding, we believe that botanic gardens are developing a new approach to their collections. We also believe that botanic gardens, because of their past experiences and current knowledge, are key to mitigating the effects of invasive species in the future.

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