Maj De Poorter
Invasive Species Specialist Group (ISSG), IUCN; Centre for Invasive Species Research, University of Auckland, Auckland, New Zealand; e-mail: [email protected]
Efforts by the Convention on Biological Diversity and International Plant Protection Convention to address the problem of movement and spread of invasive alien species have implications for pest risk analysis. National plant protection organizations responsible for pest risk assessment must deal with a wider scope of pest impacts when environmental risks are included in the analysis. They also will often face a high level of complexity in ecological interactions. This paper provides general recommendations for overcoming such difficulties and outlines how the Invasive Species Specialist Group can provide assistance.
The natural biogeographical barriers of oceans, mountains, rivers and deserts provided the isolation essential for unique species and ecosystems to evolve. In just a few hundred years these barriers have lost their effectiveness; one critical element of economic globalization is the movement of organisms from one part of the world to another through trade, transport, travel and tourism.
Many organisms have been deliberately introduced into new ecosystems in which they are alien species (as defined previously, see section 1). The Convention on Biological Diversity defines "introduction" differently from the International Plant Protection Convention as "the movement by human agency, indirect or direct, of an alien species outside of its natural range (past or present). This movement can be either within a country or between countries or areas beyond national jurisdiction" (CBD, 2002). Many of the deliberate introductions are beneficial to people for food or other economic uses. However, tremendous damage results from those that are detrimental. This paper addresses the latter group: "invasive alien species", namely those species whose introduction and/or spread threaten biological diversity.
Biological invasions by alien species are now considered the second leading factor in biodiversity loss globally; on islands, invasive alien species are considered the main factor contributing to extinctions of native vertebrates (mammals, birds etc). The impacts of invasive alien species on biodiversity and ecosystem functioning are immense, insidious and often complex. Directly or indirectly, these impacts have ramifications for sustainable development and poverty alleviation (see also: Office of Technology Assessment, 1993, Lowe et al., 2000).
As discussed in earlier chapters, Article 8(h) of the CBD requires contracting parties, as far as possible and as appropriate, to prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species. Extensive guidance on how to implement this has been provided (CBD, 2002). Meanwhile, since 1999, the IPPC has been clarifying its role with regards to invasive alien species that are plant pests. In particular, the 2003 revision of ISPM 11: Pest risk analysis for quarantine pests including analysis of environmental risks included in the coverage of environmental impacts:
These efforts by the CBD and IPPC to address the problem of movement and spread of invasive alien species have ramifications for the operations of national agencies responsible for implementing the two conventions.
Including environmental impacts in pest risk assessment means that pest risk analysis will need to deal with a wider scope of impacts and often with a high level of ecological complexity.
The wider scope of impacts would involve the inclusion of, for example, pathogens affecting wild plants. For instance, Phytophthora cinnamomi, causing dieback, is the largest threat to biodiversity in a "hotspot" of native plant communities in southwest Western Australia (Watson, 2003).
Pest risk analysis will also have to deal with ecological complexity. The complexity of impacts in native biodiversity and ecosystem functioning can be very high. National plant protection organizations will need to adapt to the requirements of treating this complexity effectively in pest risk analyses. It is instructive to ask: How prepared are NPPOs to deal with assessing an organism that may not necessarily be harmful on its own but that may allow an invasive alien species to become a "super" invasive alien species? How prepared are NPPOs to deal with the effect of invasive alien plants on such abstruse ecosystem issues as the crocodile sex ratio? How will they deal with the concept of "invasional meltdown", when primary invaders facilitate the rapid development of invasiveness of other alien species?
Examples of the complex ecological impacts that will need to be assessed by NPPOs in pest risk analysis include the following:
Some invasive alien plants influence fire cycles. This has the dual effect of threatening native plant species and positively reinforcing the invasive alien plant’s advantages (D’Antonio, 2000).
In New Zealand there is no evidence that exotic conifers can utilize indigenous mycorrhizal fungi. It is possible that this is a factor that restricts the spread of these conifers into New Zealand’s native forests. However, the fly agaric (Amanita muscaria), an exotic ectomycorrhizal mushroom, is often found as a mycorrhizal associate of introduced conifers (Pinus spp., Pseudotsuga menziesii). Once this fungus is established in the native forests, what is the risk that the exotic conifers may follow (Johnston, 2002)?
In a study from 1994 to 1997 in South Africa, it was observed that the majority of Lake St Lucia’s nesting Nile crocodiles selected open, sunny, sandy areas in which to deposit their eggs. Nests were found only in shaded sites in the Mpate river breeding area; these nests were shaded primarily by an invasive alien plant, Chromolaena odorata. Shaded site soil temperatures at 25 cm depth were on average 5.0 - 6.0 °C cooler than sunny site soil temperatures at the same depth. Shaded site temperatures were well below the pivotal temperature for St Lucia’s Nile crocodiles and as a result a female-biased sex ratio would be expected (Leslie and Spotila, 2000).
A Pacific Island provides a notable illustration of "invasional meltdown" of ecological complexity. Alien tramp ants, also known as yellow crazy ants (Anoplolepis gracilipes), have formed extensive super colonies on Christmas Island (an Australian territory) since the mid-1990s. Red crabs are highly vulnerable to these yellow crazy ants. The extirpation of the native land crab population has had manifold consequences for the dynamics and structure of the native forest. It is also facilitating secondary invasions. This includes facilitation by the crazy ants (in the absence of red crabs) of invasion of native rainforest by the giant African snail (Achatina fulica), woody alien weeds and alien cockroaches (Green, O’Dowd and Lake, 2001).
In addition to such issues of capability in dealing with ecological complexity in pest risk analysis, there are questions at the level of the overall system. The Agreement on the Application of Sanitary and Phytosanitary Measures (WTO, 1994) is designed to facilitate free trade. Hence its focus is on international obligations to ensure that import restrictions are not a disguised form of commercial protectionism. The SPS Agreement’s mandate does not include ensuring that governments’ standards are adequate to protect environments and biodiversity from the undesirable side-effects of free trade, such as the massive increase in risk of invasions by alien species (Jenkins, 1999). However, discussion of whether or not the SPS system allows for effective dealing with ecological invasive alien species is beyond the scope of this paper.
Agencies such as NPPOs deserve the support and encouragement of the international community in tackling the difficulties of maximizing biodiversity outcomes in implementing both the IPPC and the CBD. Recommendations include:
For example, the New Zealand Ministry of Agriculture and Forestry developed an import health standard for spiders on table grapes. This is based on the fact that the commodity is a plant, even though the main concern about the spiders is their potential impact on native invertebrates (and human health), rather than on grapes (plants).
NPPOs have a major role to play here. The making or breaking of new attitudes to consultation, environment and thinking outside the box is often in the hands of NPPOs (or similar agencies), given their relative power within government systems and their resourcing compared with other agencies. NPPOs face challenges, but also have major opportunities to contribute to stemming the tide of biodiversity loss, species extinctions and resulting livelihood impacts.
The IUCN Invasive Species Specialist Group serves as an active network of people knowledgeable about invasive species problems and those requiring assistance in their fight against biological invasions. The Office of ISSG is located at the University of Auckland, New Zealand. Its role is global and includes:
providing technical and policy advice
increasing the awareness in the wider community about the biodiversity impacts from invasives and about management options
facilitating exchange of information and expertise about prevention, control and eradication of invasive alien species
publishing the Aliens newsletter bi-annually, providing interesting and timely information on invasive species and associated issues
managing Aliens-L
This is a listserver dedicated to invasive alien species that threaten biodiversity. It allows users to freely seek and share information on invasive alien species and related issues. Participation from all who are interested in the invasive species problem is welcome.
managing and maintaining the Global Invasive Species Database
This database was developed as part of the global initiative on invasive species led by the Global Invasive Species Programme. It focuses on invasive species that threaten biodiversity and covers all taxonomic groups from microorganisms to animals and plants. Species information, supplied or reviewed by expert contributors from around the world, includes impacts, ecology, distribution, management information, references, contacts, links and images.
coordinating and managing the Cooperative Initiative on Invasive Alien Species on Islands.
The objective of this initiative is to facilitate cooperation in key areas of invasive alien species management where it will generate a significant improvement in the conservation of island biological diversity. This includes prevention of new invasions and building local and regional capacity on ecological aspects of pest risk analysis.
References
CBD. 2002. Sixth Conference of the Parties, The Hague, the Netherlands, 7 - 19 April 2002: Decision VI/23: Alien species that threaten ecosystems, habitats or species to which is annexed Guiding principles for the prevention, introduction and mitigation of impacts of alien species that threaten ecosystems, habitats or species (available at www.biodiv.org).
D’Antonio, C.M. 2000. Fire, plant invasions, and global changes. In H.A. Mooney & R.J. Hobbs, eds. Invasive species in a changing world, pp. 65 - 93. Washington, DC, USA, Island Press. 384 pp.
Green P.T., O’Dowd, D.J & Lake, P.S. 2001. From resistance to meltdown: secondary invasion of an island rain forest. In K.N. Ganeshaiah, R. Uma Shaanker & K.S. Bawa, eds., Tropical ecosystems: structure, diversity and human welfare, pp. 451 - 455. Proceedings of the International Conference on Tropical Ecosystems, Bangalore, India, 15 - 18 July 2001. New Delhi, India, Oxford-IBH. 791 pp.
Jenkins, P. 1999. Avoiding a rat-infested, zebra mussel-fouled, nasty weed patch for a planet: global policy changes needed to stop biological invasions caused by international trade. Presented at the Workshop on Legal and Institutional Dimensions of Invasive Alien Species Introduction and Control, Bonn, Germany, 10 - 11 December 1999.
Johnston, P.R. 2002. Pers. comm., IUCN Aliens-l listserver, 31 July 2002. Linked to report by P.R. Johnston and P.K. Buchanan, Landcare Research, New Zealand, on their research [1997 - ] funded by the New Zealand Foundation for Research Science and Technology (available at www.landcareresearch.co.nz).
Leslie, A.J. & Spotila, J.R. 2002. Alien plant threatens Nile crocodile breeding in Lake St Lucia, South Africa. In C. Zachariades, R. Muniappan & L.W. Strathie, eds. Proceedings of the Fifth International Workshop on biological control and management of Chromolaena odorata, Durban, South Africa, 23 - 25 October 2000, p. 118. Pretoria, South Africa, ARC-PPRI Publications. 186 pp.
Lowe, S., Browne, M., Boudjelas, S. & De Poorter, M. 2000. 100 of the world’s worst invasive alien species: A selection from the Global Invasive Species Database. Auckland, New Zealand, IUCN/SSC Invasive Species Specialist Group (ISSG). 12 pp. Booklet distributed with Aliens 12, December 2000 (available at www.issg.org).
Office of Technology Assessment [of the U.S. Congress]. 1993. Harmful non-indigenous species in the United States. OTA-F-565. Washington, DC, USA, U.S. Government Printing Office (available at www.wws.princeton.edu). viii + 391 pp.
Watson, J. 2003. Small is beautiful: conserving the nature of low altitude mountain protected areas in South Western Australia. Presented at the World Heritage Mountain Protected Areas Workshop, Drakensberg, South Africa, 4 - 8 September 2003, at the occasion of the Fifth World Parks Congress, 8 - 17 September 2003, Durban, South Africa.
WTO. 1994. Agreement on the application of sanitary and phytosanitary measures. In: Agreement establishing the World Trade Organization: Annex 1A: Multilateral agreements on trade in goods. Geneva, Switzerland (available at www.wto.org).
