Biodiversity and Conservation

, Volume 17, Issue 8, pp 1979–1995 | Cite as

Assessing the risks of plant invasions arising from collections in tropical botanical gardens

  • Wayne Dawson
  • Ahmed S. Mndolwa
  • David F. R. P. Burslem
  • Philip E. Hulme
Original Paper


Tropical botanical gardens have played an important role in the distribution, naturalisation and spread of non-native plants worldwide. Appropriate guidance relating to risk assessments of established botanical garden collections is often scarce. This paper uses the Amani Botanical Garden (ABG), Tanzania, as a case study to highlight appropriate methods to assess the risks posed by existing and future collections in tropical botanical gardens. Key considerations included field assessments of species status using accepted definitions of naturalisation, spread and invasion, distinguishing between intentionally and unintentionally introduced species, identifying taxonomic patterns in invasion status, assessing patterns in habitats colonised, and determining how knowledge of invasion elsewhere might be useful in forecasting risk. Out of the 214 alien plant species surviving from the original plantings in the early 20th century, 35 had only regenerated, 38 had locally naturalised while 16 had spread widely in the botanical garden. A further 16 species with unclear introduction records in the garden were also found to be naturalised. A greater proportion of introduced species were potentially invasive than might be expected from previous analyses of global floras. Overall, just over half of all naturalised and spreading species were also observed in forest fragments and edges. The proportion of species that had been recorded elsewhere as naturalised/invasive was significantly related to their status in ABG, with 94% of spreading species and 79% of naturalising species being recorded as naturalised or invasive elsewhere, compared to 57% of species that were only regenerating and 49% of species only surviving. Recommendations for further risk assessments of botanical garden collections are discussed.


Alien Exotic Horticulture Invasion Naturalisation Risk assessment Weeds Tanzania 



Amani Botanical Garden



This work is part of the Darwin Initiative project “Combating alien invasive plants threatening the East Usambara mountains in Tanzania” (162/13/033) and authors are grateful for financial support from Defra and NERC. The authors would also like to thank the staff of the Amani Nature Reserve, especially Mr. Corodius Sawe, and the Tropical Biology Association, especially Dr. Rosie Trevelyan, for logistical support.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Wayne Dawson
    • 1
    • 2
  • Ahmed S. Mndolwa
    • 3
  • David F. R. P. Burslem
    • 1
  • Philip E. Hulme
    • 4
  1. 1.School of Biological sciencesUniversity of AberdeenAberdeenUK
  2. 2.Centre for Ecology and Hydrology (Edinburgh)Penicuik, MidlothianUK
  3. 3.Tanzanian Forestry Research Institute (TAFORI) HerbariumLushotoTanzania
  4. 4.National Center for Advanced Bio-Protection TechnologiesLincoln UniversityCanterburyNew Zealand

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