Citation Detail: Jeffrey A. McNeely. 1996. HUMAN DIMENSIONS OF INVASIVE ALIEN SPECIES:HOWGLOBALPERSPECTIVES ARE RELEVANT TO CHINA . in: Conserving China's Biodiversity (II) (PETER Johan Schei, WANG Sung and XIE Yan eds.). China Environmental Science Press. Beijing. 169-181p.

HUMAN DIMENSIONS OF INVASIVE ALIEN SPECIES:
HOW GLOBAL PERSPECTIVES ARE RELEVANT TO CHINA

Jeffrey A. McNeely
(IUCN, Gland, Switzerland)

★INTRODUCTION★HISTORICAL DIMENSIONS ★HUMAN DIMENSIONS OF THE CAUSES OF SPECIES INVASIONS★HUMAN DIMENSIONS OF THE CONSEQUENCES OF INVASIVE ALIEN SPECIES★HUMAN DIMENSIONS OF THE RESPONSE TO IAS★CONCLUSIONS

ABSTRACT
The great increase in the introduction of alien species that people are importing for economic, aesthetic, accidental, or even psychological reasons is leading to more species invading native ecosystems, with disastrous results: they become invasive alien species (IAS) that have significant deleterious effects on both ecosystems and economies. This paper examines some of the important human dimensions of the IAS problem, including historical, economic, cultural, linguistic, health, psychological, sociological, management, legal, military, philosophical, ethical, and political dimensions. These are addressed in terms of the causes, the consequences, and the responses to the problem of IAS. It is apparent from this overview that the human dimensions of IAS are fundamental, and that successfully addressing the problem will call for greater collaboration between different economic sectors and among a wide range of disciplines. The Convention on Biological Diversity and many other international agreements offer important opportunities for addressing the complex global problems of IAS through improved international cooperation.

INTRODUCTION

Human impacts on the ecosystems of our planet continue to grow. Our increasing population and expanding levels of consumption mean that more people are consuming more of nature's goods and services, pushing against the limits of sustainability. Greatly expanding global trade is feeding this consumption, with large containers of goods moving quickly from one part of the world to another by plane, ship, train, and truck.

One critical element in this economic globalization is the movement of organisms from one part of the world to another through trade, transport, travel, and tourism. Many of these movements of organisms into new ecosystems where they are alien (also called non-native, non-indigenous or exotic) are generally beneficial to people. But many others have very mixed impacts, benefiting some individuals or interest groups while disadvantaging others. And in a few cases, especially disease organisms and pests of forests or agricultural crops, the alien species is clearly detrimental to all, or nearly so. The latter groups are known as "invasive alien species" (IAS), that subset of alien species whose establishment and spread threatens ecosystems, habitats, or species with economic or environmental harm (GISP, 2001).

Farmers have been fighting weeds since the very beginnings of agriculture, and disease organisms have been a major focus of physicians for well over a hundred years. But the general global problem of invasive alien species has been brought to the world's attention only relatively recently by ecologists who were concerned that native species and ecosystems were being disrupted (e.g., Elton, 1958; Drake et al., 1989). Much of the work to date on IAS has focused on their biological and ecological characteristics, the vulnerability of ecosystems to invasions, and the use of various means of control against invasives. However, the problem of IAS is above all a human one, for at least the following reasons:

• People are largely responsible for moving eggs, seeds, spores, vegetative parts, and whole organisms from one place to another, especially through modern global transport and travel;
  
• While some species are capable of invading well-protected, "intact" ecosystems, IAS more often seem to invade habitats altered by humans, such as agricultural fields, human settlements, and roadways;
  
• Many alien species are intentionally introduced for economic reasons, a major human endeavour, and
  
• The dimensions of the problem of invasive alien species are defined by people, and the response is also designed and implemented by people, with differential impacts on different groups of people.

People introduce organisms into new habitats non-intentionally (often invertebrates and pathogens), intentionally (usually plants and vertebrates), or by inadvertence when organisms imported for a limited purpose then subsequently spread into new habitats (Levin, 1989). Many of the deliberate introductions relate to the human interest in nurturing species that are helpful to people, for agricultural, forestry, ornamental, or even psychological purposes (Staples, 2001). The great bulk of human dietary needs in most parts of the world are met by species that have been introduced from elsewhere (Hoyt, 1992); it is difficult to imagine China without potatoes, tomatoes, cattle, or maize -- all introduced species. Species introductions, therefore, are an essential part of human welfare and local cultures in virtually all parts of the world. Further, maintaining the health of these introduced alien species of undoubted net benefit to humans may sometimes require the introduction of additional alien species for use in biological control programmes which import natural enemies of, for example, agricultural pests (Waage, 1991; Thomas and Willis, 1998), but these biological controls may themselves sometimes become invasive.

Considerable evidence indicates a rapid recent growth in the number and impact of IAS (Mooney and Hobbs, 2000). Trade, and more generally economic development, lead to more IAS; Vilà and Pujadas (2001), for example, found that countries that are more effectively tied into the global trading system tend to have more IAS, being positively linked to the development of terrestrial transport networks, migration rates, number of tourists visiting the country, and trade in commodities (Dalmazzone, 2000). The general global picture shows tremendous mixing of species, with unpredictable long-term results but a clear trend toward homogenization (Bright, 1998; Mooney and Hobbs, 2000). The future is certain to bring considerable additional species shuffling as people continue to influence ecosystems in various ways, not least through both purposeful and accidental introduction of species as an inevitable consequence of growing global trade. This shuffling will yield species that become more abundant and many others that will decline in numbers (or even become extinct) but the overall effect will likely be a global loss of biodiversity at species and genetic levels. But how is the "great reshuffling" of species being driven by human interests and how will it affect them? How should people think about the issue? What stakes are involved? Whose interests are being affected? And how can the human dimensions be best addressed by scientists, resource managers, and policy makers?

These are not trivial questions, because the issue of IAS has ramifications throughout modern economies. It involves global trade, settlement patterns, agriculture, economics, health, water management, climate change, genetic engineering and many other fields and concerns. It therefore goes to the very heart of problems policy-makers are spending much time debating, ironically usually without reference to IAS. This paper draws on contributions presented at a workshop held in Cape Town, South Africa, on 15-17 September 2000, under the auspices of The Global Invasive Species Programme (GISP). The workshop examined some of the ramifications of IAS through many dimensions of human endeavour, including historical, economic, cultural, linguistic, health, psychological, sociological, legal, management, military, philosophical, and political components. The conclusion was that IAS are deeply woven into the fabric of modern life. While the biological dimensions of IAS are fundamental, more effective responses to the problems they pose must incorporate the kinds of human dimensions that are discussed in this paper.

HISTORICAL DIMENSIONS

Because of a long geological and evolutionary history, our planet has very different species of plants, animals, and micro-organisms on the various continents, and in the various ecosystems. As a broad illustration, pandas live in mountain forests, chiru live in Tibetan steppes, and elephants are confined in China to forests in Yunnan. Geographical barriers have ensured that most species remain within their region, thus resulting in a much greater species richness across the planet than would have been the case if all land masses were part of a single continent. This historical biogeographical framework provides the basis for defining concepts of native and alien species. It is also important to recognize that biogeography is dynamic, as species expand and contract their ranges and the contents of ecosystems change as a result of factors such as climate change (Udvardy, 1969).

Humans apparently evolved in Africa, then Homo sapiens spread to Europe and Asia over 100,000 years ago, Australia 40-60,000 years ago, the Americas about 15-20,000 years ago, and the far reaches of the Pacific less than 1000 years ago. Our species is a good example of a naturally invasive species, spreading quickly, modifying ecosystems through the use of fire, and driving other species to extinction (Martin and Klein, 1984). Wherever people have moved they have also carried other species with them. The Asians who first peopled the Americas, for example, were accompanied by dogs, and Polynesians sailed with pigs, taro, yams, and at least 30 other species of plants (and rats and lizards as stowaways).

Trade is known far back in human prehistory, judging from the discovery of stone tools at a considerable distance from where they were quarried. But as long-distance travel became more regular, trade became more important. Chinese traders have sailed into Southeast Asia for at least several thousand years, and trading routes between China, India and the Middle East stretch back at least as long. As sailing craft became larger and more reliable, trade increased further and was given a great boost with the voyages of Christopher Columbus that opened up entirely new sources of species, and led to the replacement of the rigid moral strictures of Medieval Europe by a new set of merchant values that stressed consumption (Low, 2001).

For at least several thousand years, armies have been an important pathway for moving species from one region to another, with at least some of these becoming invasive (like the armies). The spread of new diseases by armies is well known. For example, measles were carried into the Americas from Europe by the early conquistadors and perhaps syphilis went in the opposite direction (McNeill, 1976). Rinderpest, a virus that is a close relative of measles and canine distemper, is native to the Steppes of Central Asia, but it frequently swept through Europe, being carried by cattle moved to feed armies during military campaigns. Africa remained free of this disease until 1887, when it appeared in Eritrea at the site of the Italian invasion, spreading through Ethiopia in 1888 and conquering the entire continent in less than a decade. In some parts of Africa, rinderpest was followed by wars and cattle raids as the tribal pastoralists sought to maintain their herds (Pearce, 2000). Another result was that rinderpest led an ecological revolution against people and cattle and in favour of wildlife species that were resistant to the disease.

The period of European colonialism into North America, Australia, New Zealand and elsewhere ushered in a new era of species introductions, as the European settlers sought to recreate the familiar conditions of home (Crosby, 1986). They took with them species such as wheat, barley, rye, cattle, pigs, horses, sheep, and goats, but in the early years their impacts were limited by the available means of transport. Once steam-powered ships came into common use, the floodgates opened and over 50 million Europeans emigrated to distant shores between 1820 and 1930, carrying numerous plants and animals that were added to the native flora and fauna (Reichard, 2001). More recently, Chinese, Indian, Indo-Chinese, African, and other emigrants have carried familiar species with them to grow in their new homelands in Europe, Australia, and the Americas.

Thus the faunal and floral assemblages found in any particular location have been profoundly influenced by past human activities, and people are likely to have an even greater impact in the future. This leads to the contemplation of whether the current episode of globalization might lead to increased diversity in at least some places after the dust settles on the current extinction spasm (Parker, 2001). As just one example, New Zealand has twice as many plants today as it did when humans first arrived, as well as a whole suite of new mammals; one tragic cost was the loss of an extensive unique fauna of birds. Further development of biotic communities as climates change will depend on organisms invading into novel habitats, sometimes hybridizing with the native species, sometimes replacing them, and sometimes adding to the diversity of the ecosystem with new species interactions. Through introducing species, humans are creating their own ecosystems (Orr and Smith, 1998), often more or less by accident, and disrupting ecosystems that had evolved over millions of years.

HUMAN DIMENSIONS OF THE CAUSES OF SPECIES INVASIONS

Global trade has enabled modern societies to benefit from the unprecedented movement and establishment of species around the world. Agriculture, forestry, fisheries, the pet trade, the horticultural industry, and many industrial consumers of raw materials today depend on species that are native to distant parts of the world. The lives of people everywhere have been greatly enriched by their access to a greater share of the world's biological diversity, and expanding global trade is providing additional opportunities for further such enrichment. Most people warmly welcome this globalization of trade, and growing incomes in many parts of the world are leading to increased demand for imported products. North American nursery catalogues, for example, offer nearly 60,000 plant species and varieties to a global market, often through the Internet (Ewel et al., 1999). A generally unrecognized side effect of this globalization is the introduction of alien species, at least some of which may be invasive.

Linked to the global marketplace, the world is becoming increasingly urban, with half the world's population living in cities at the turn of the century. Cities tend to be the focal points of the global economy and the entry points for many invasives. Many invasive species are most prolific in urban and urban-fringe environments where long histories of human disturbance have created abundant bare ground and many opportunities for invasion. Many urban dwellers seek ornamentals from a wide range of sources, and these may become invasive. For example, Berlin has 839 native species of plants and 593 aliens (Kowarik, 1990). Urbanization involves large and mobile populations that can easily escape the environmental penalties from mis-using resources. Further, they are seldom aware of the problems of invasive species because they have essentially lost their connections to the natural environment (Staples, 2001). Settlement patterns also involve transportation links, and the distribution of many invasives seem to follow transportation corridors. Thus human settlement patterns, too, are part of the invasive species issue (Marambe, et al., 2001).

Many people who seek to introduce a non-native species into a new habitat do so for an economic reason (McNeely, 1999). They may wish to increase their profits from agriculture, they may believe that the public will like a newly-discovered flower from a distant part of the globe, or they may think that non-native species will be able to carry out functions that native species cannot carry out as effectively. But few of those introducing alien species have carried out a thorough cost-benefit analysis before initiating the introduction, ignoring ("externalizing") the negative impacts that may follow from species introductions because they have not been required to recognize them. They might also be worried that they would be expected to compensate those who are negatively affected.

Similarly, those who have been responsible for inadvertently introducing species into new habitats may not have been willing to make the investment necessary to prevent such accidents from occurring. They may not have realized the dangers, and in any case the dangers would be unlikely to have much economic impact on their own welfare. Rather, the costs of such accidents are borne disproportionately by people other than those who are permitting the accidents to happen. Thus the costs of introducing potentially invasive alien species into new habitats are externalized in considerations of the costs of global trade. The line of responsibility is insufficiently clear to bring about the necessary changes in behaviour, so the general public and future generations end up paying most of the costs.

One limitation of human perception of the costs of IAS is that invasions often happen almost invisibly, without any clear responsibility, and with very limited initial impacts. Further, monitoring, early detection, and containment of invaders before they cause widespread damage are unlikely to be considered to have a positive cost-benefit ratio because the costs are required now while the main benefits (at least in terms of future costs avoided) remain speculative. On the other hand, where sound cost-benefit studies have been done, they demonstrate the value of control, and prevention is shown to be the best strategy (Jenkins, 2001).

HUMAN DIMENSIONS OF THE CONSEQUENCES OF INVASIVE ALIEN SPECIES

IAS have many negative impacts on human economic interests. Weeds reduce crop yields, increase control costs, and decrease water supply by degrading catchment areas and freshwater ecosystems. Tourists unwittingly introduce alien plants into national parks, where they degrade protected ecosystems and drive up management costs. Pests and pathogens of crops, livestock and trees destroy plants outright, or reduce yields and increase pest control costs. The discharge of ballast water introduces harmful aquatic organisms, including diseases, bacteria and viruses, to both marine and freshwater ecosystems, thereby degrading commercially important fisheries and recreational opportunities. And recently-spread pathogens continue to kill or disable millions of people each year, with profound social and economic implications. While considerable uncertainty remains about the total economic costs of invasions, estimates of the economic costs of particular invasives to particular sectors indicate the seriousness of the problem. Some of these, drawn primarily from Perrings et al., 2000, have been collected in Box 1. Many of these estimates remain controversial among economists.

BOX 1: INDICATIVE COSTS OF SOME ALIEN INVASIVE SPECIES (costs in US$)

Globalization is bringing with it a series of new medical threats, many of which can be considered a sub-set of the IAS problem. Viruses are a particular problem because they are so difficult to combat; while vaccines for viruses such as smallpox, polio, and yellow fever have proven effective, cures remain elusive and even very substantial investments to find a cure for AIDS have thus far proven only marginally effective. Even worse, the global changes that are affecting many parts of the world are expected to lead to the expansion of the ranges of many viruses that are potentially dangerous to humans. When people move into formerly unoccupied wilderness areas, this brings them into contact with a wider range of viruses and bacteria, while air travel carries them around the globe before the symptoms become apparent.

Infectious disease agents often, and perhaps typically, are invasive alien species (Delfino and Simmons, 2000). Unfamiliar types of infectious agents, either acquired by humans from domesticated or other animals, or imported inadvertently by travellers, can have devastating impacts on human populations. Pathogens can also undermine local food and livestock production, thereby causing hunger and famine. Examples:

The bubonic plague (caused by Pasturella pestis) spread from central Asia through north Africa, Europe, and China using a flea vector on an invasive species of rat (Rattus rattus) that came originally from India.

The viruses carrying smallpox and measles spread from Europe into the western hemisphere shortly following European colonization. The low resistance of the indigenous peoples to these diseases helped bring down the mighty Aztec and Inca empires.

The influenza A virus has its origins in birds but multiplies through domestic pigs which can be infected by multiple strains of avian influenza virus and then act as genetic "mixing vessels" that yield new recombinant-DNA viral strains. These strains can then infect the pig-tending humans, who then infect other humans, especially through rapid air transport.

The dynamism among invasive pathogens, human behaviour, and economic development are complex and depend on interactions between the virulence of the disease, infected and susceptible populations, the pattern of human settlements, and their level of development. Large development projects, such as dams, irrigation schemes, land reclamation, road construction and population resettlement programmes, have contributed to the invasion of diseases such as malaria, dengue, schistosomiasis and trypanosomiasis. The clearing of forests in tropical regions to extend agricultural land has opened up new possibilities for wider transmission of viruses that carry haemorrhagic fevers that previously circulated benignly in wild animal hosts. Invasive species combined with variations in inter-annual rainfall, temperature, human population density, population mobility and pesticide use all contribute to one of the most profound human dimensions of invasive species: the threat to human health.

Components of biological diversity that are threatened or lost as a result of IAS can lead to the loss of traditional knowledge, innovations and practices. Likewise, customary uses of biological resources in accordance with traditional cultural practices may be inhibited or, in the worst case, discontinued completely. As intimate users of local biological resources, indigenous and local communities potentially are best-qualified to monitor the impacts of alien species on local ecosystems and their components (Article 7 of the Convention on Biological Diversity), to identify when those species become invasive, and to be involved in eradication and mitigation programmes (Article 8h of the CBD). But this depends on awareness of the problem. In China, Vietnam, Malaysia, Thailand, Korea, and Cambodia (at least), people "make merit" by releasing captive animals, especially birds, fish, and turtles; but one study found that 6% of birds released were exotic, and most of the fish and turtles were captive-bred exotic species that could become invasive (Severinghaus and Chi, 1999). Clearly, the cultural process of "making merit" does not intentionally include deleterious impacts on native ecosystems, largely because the people involved are urban dwellers who have no concept of IAS.

HUMAN DIMENSIONS OF THE RESPONSE TO IAS

This paper says relatively little about the actual management of IAS, which is well covered by GISP (2000). But generally speaking, GISP advocates four main management approaches: first, subject all alien species proposed for introduction to expert consideration, following the precautionary principle; second, improve the scientific basis for predicting which species proposed for deliberate introduction are likely to become invasive and which are likely to be beneficial; third, improve control of pathways for unplanned introductions (through ballast water, international trade, wooden packing material, and so forth); and fourth, improve management techniques to eradicate or control invasive alien species once prevention has failed or become impractical.

Human societies seem to have a great capacity for contradiction, with quarantine inspections, for example, being the responsibility of the same governments that promote globalization that undermine government capacity to apply effective quarantine measures (Low, 2001). Governments have a responsibility to provide regulations in the public interest, but current economic orthodoxy argues that global trade is fostered through removing regulations that may constrain such trade, such as restrictions that may limit the introduction of a potentially invasive alien species. These contradictions help to underline the conflict of interests between global trade and the control of IAS, and the challenges to current management measures and legal frameworks.

The human dimension is the most unpredictable variable in any management programme to control IAS. Reaser (2001) and Mack (2001) demonstrate that IAS are a by-product of human values, decisions, and behaviours, suggesting that a focus on human beliefs and resultant behaviour might be more effective than focusing primarily on IAS themselves as the problem. Resource managers must therefore generate public support and understanding for any control programme before a project begins. Thus, "social embedding" of management actions, as through the "Working for Water Programme" in South Africa (Noemdoe, 2001), can foster effective management intervention.

Economic arguments have much to contribute to programmes to address the problems of IAS (Perrings et al., 2000). Decision-makers often find arguments couched in economic terms to be more convincing than those cast in emotive or ethical terms, and economics-based arguments of costs and benefits can be used to support stronger programmes to deal with invasive species.

Some methods of controlling IAS may carry health hazards as well. For example, pesticides can have serious effects on both people and ecosystems. Between 1975 and 1985, forests in Atlantic Canada were sprayed with the insecticide Matacil to control spruce budworm (Choristoneura fumiferana). In the late 1990s, fisheries and environmental scientists inferred that the declines in the Atlantic salmon (Salmo salar) stocks in the Restigouche River that occurred at that time were related to the exposures of the smolt to nonylphenol used as an inert solvent in the pesticide (Fairchild et al., 1999).

Once public enthusiasm to control IAS has been generated, it must be channelled in the right direction. For example, gorse (Ulex europeus) has become invasive in montane grasslands of Sri Lanka following its introduction about 150 years ago. Recently, several local NGOs have launched volunteer programmes to remove gorse. However, several species of endemic reptiles and amphibians have found gorse a congenial habitat, providing food and cover. When the eradication programmes removed this habitat virtually overnight, the endemic species were exposed to native opportunistic predators such as crows (Marambe et al., 2001). Therefore, programmes to eradicate invasive species of plant also need to consider restoring the ecological functions of the species that are removed.

Over 40 international conventions, agreements, and guidelines have been enacted for addressing the problem of IAS, at least in part, and many more are being prepared (Shine et al., 2000). Governments have expressed their concerns about the problem of IAS especially through the Convention on Biological Diversity (CBD), which calls on the Parties to "prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats, or species" (Article 8h). But the expanding impact of IAS on both global economies and the environment implies that these international instruments have been insufficient to prevent and combat IAS effectively, suggesting that additional measures, such as a protocol under the CBD, are advisable.

The invasive alien species issue can be seen as ultimately an ethical concern. If people are seeking to maximize their material welfare, or even the diversity of species with which they surround themselves, alien species might well be a part of their rational response. But when alien species become invasive, destabilizing ecosystems and reducing diversity, then control is a far more acceptable, even necessary, response. Since invasions invariably involve trade-offs, the determination of costs and benefits of IAS becomes paramount (though this too has its ethical components).

Thus the concept of invasive alien species is not purely dependent upon objective ecological criteria, but also on human concepts used to identify origin, authenticity, and responsibility

CONCLUSIONS

IAS are able to invade new habitats and constantly extend their distribution, thereby representing a threat to native species, human health, or other economic or social interests. One remarkable human dimension is the fact that a strong consensus can be built that many specific invasions are harmful, including killer bees, water hyacinth, spruce budworms, various pathogens, and agricultural weeds. The issue of IAS, therefore, can bring together interest groups that might otherwise be in opposition, such as farmers and conservation groups. Bringing in the human dimensions can shift the focus from the IAS itself to the human actions that facilitate its spread or manage its control, and implies that focussing directly on the invasive species is likely to provide only symptomatic relief. A more fundamental solution requires addressing the ultimate human causes of the problem, often the economic motivations that drive or enable species introductions.

This paper has identified some of the human dimensions involved in IAS. It is apparent that these dimensions are interconnected, and are relevant in different degrees in different countries, or with different species of invasives. But the presence of so many human dimensions implies that approaches to management need to involve many sectors of modern society, including trade, tourism, industry, the military, public health, and so forth. Addressing the problem will call for more collaboration between ecologists, geographers, land use planners, economists, sociologists, psychologists and people from other disciplines to investigate the human dimensions of biological invasions.

The complex relationship between globalization and invasion pathways is perhaps the most important human dimension of IAS, and should be occupying the minds of policy makers in the next few decades (Carleton and Ruiz, 2000). Globalization carries with it the rise of transnational corporations, international financing, and multi-media marketing that undermine the political power of most governments, weakening their ability to regulate economic behaviour in the public benefit (Hattingh, 2001). One important implication is that concern about IAS needs to be expressed in terms of the threats to the resource base of the global economic system, which translates into monetary figures. Thus many of those who are concerned about the problems of IAS have quite properly turned to economics to argue their case.

Humans, with all their diversity of quirks, strengths, and weaknesses, are at the heart of the problem of IAS and, paradoxically, also at the heart of the solution. Given the ultimate human motivations of survival and reproduction, and perhaps spiritual fulfilment, and the more immediate economic motivations, people might be encouraged to contribute to addressing the problem of IAS by such measures as:

Helping the public to identify and embrace values that have a direct relationship to basic needs and are environmentally sound, thereby also achieving longer term benefits. This might include promoting the concept of "community", including native species, as a value that can balance the powerful economic values of globalized trade.

Developing conservation practices and ethics that emphasise the importance of natural ecosystems, for example by refining distinctions between natural and anthropogenic conditions, devising ways to use ecosystems without losing biotic diversity, and facilitating shifts in societal values toward more respect for nature.

Identifying measures that work within existing value systems, but encourage people to support conservation measures (for example, through the use of economic incentives and disincentives).

Ensuring that the costs of controlling IAS are "internalized", paid by those who are benefiting from intentional introduction and those responsible for unintentional introductions.

Linking the concern about invasive alien species to the drive for development that motivates most people, and virtually all governments, today.

Including human dimensions in the various conventions, agreements, and guidelines on IAS, such as those developed under the Convention on Biological Diversity.

When introducing new species, use risk assessment procedures that take into account future changes in usage and demonstrate that -- to the best of current knowledge -- detrimental impacts will be limited.

A fundamental constraint against changing the way people behave in regard to IAS is that few people in any part of the world consciously perceive that they have been affected negatively by IAS, either directly or indirectly. While the Global Invasive Species Programme has been reasonably successful in developing technical information for resource managers, the supply of information on IAS to the general public remains generally poor, so that most people have little idea of which species are invasive, what are their impacts, and what are appropriate control methods. In the absence of such information, inappropriate responses can be expected. On the other hand, human perceptions are filtered by the media, the availability of information, and language, and all of these can be influenced to limit the spread of IAS.

It is remarkable that some agencies that should know better are actually promoting IAS in the name of development. For example, development assistance agencies often seem to prefer to introduce alien species (especially from the country providing the funding for the assistance), rather than promoting native species. Even UN agencies, such as FAO, are widely promoting numerous weedy trees, shrubs, fodder grasses and legumes that are known to be highly invasive in at least some countries.

Broader public support needs to be based on a stronger foundation of science. Despite decades of research, scientific knowledge of the biology, ecology, and human dimensions of invasive alien species remains very incomplete. With no more than 20% of the world's species even scientifically described, scientists simply are unable to predict which species are likely to become invasive or to assess the precise ecological, social or economic impact they are likely to have. With such incomplete knowledge, we risk unexpected consequences any time a new species is introduced into an ecosystem. Unpredicted effects, such as the hole in the ozone layer, global warming, mad cow disease, pesticide accumulation, the impacts of hormones in the environment, and so forth, can result from seemingly beneficial products and procedures. It therefore seems sensible to do everything we can to ensure that we err on the side of precaution, perhaps on occasion sacrificing some economic profit for the businesses directly involved while helping to ensure a healthier future for all of society. Thus we should also strongly support research to assess the risks of invasive alien species and to find effective means of dealing with the risks.

Research priorities for human dimensions of IAS include:

Identifying conflicting interests regarding benefits and risks of introductions, substantiating evaluations of those benefits and risks, and determining the likely distribution of benefits and risks among sectors of society (Ewel et al., 1999).

Identifying underlying causes for human choice in relation to IAS, including identifying how human beliefs about specific invasive species influence their actions to promote or limit the spread of that species.
Evaluating potentially useful indigenous organisms rather than non-indigenous ones, thereby reducing incentives for introductions.

Elucidating the interactions between the media, the public, and scientists/ conservationists.
Identifying the views of various interest groups about invasive alien species.
Carrying out a predictive modelling exercise to project what might be the outcome if we are unable to slow or stop the spread of IAS.

This paper has sought to clarify basic economic, social, psychological, ethical, and political elements about IAS, but the challenge has been considerable and it appears that each case needs to be considered on its own merits. That said, here are some human dimensions elements to consider in addressing any IAS problem:

Ensure that those who are most directly affected by the IAS are involved in decisions about how to manage the problem.

Build sufficient public information programmes into each effort, investing more in this regard where the problem is likely to involve controversial techniques (such as use of poisons).

Conduct a detailed analysis of human dimensions as these affect the interested parties, including the general public and decision makers.
Build linkages between the management of IAS and development, through involving economic sectors such as health, energy, agriculture (food security), forestry, and fisheries.

Establish general principles for guiding policies that explicitly promote the identities and values that motivate and direct people to minimize the spread of IAS.

Because we can never be certain about the behaviour of an alien species imported into a new environment, we should do everything possible to prevent unwanted invasions, carry out careful assessments before intentionally introducing an alien species into a new environment, build a stronger awareness among the general public about the problems of IAS, and build an ethic of responsibility among those most directly involved in the problem. The global trading system brings many benefits but it needs to be managed in a way that minimizes any deleterious impacts of invasive alien species on ecosystems, human health, and economic interests. Human dimensions are central in doing so.

REFERENCES
Bangsund, D.A, F.L. Leistritz, and J.A. Leitch. 1999. Assessing economic impacts of biological control of weeds: The case of leafy spurge in the northern Great Plains of the United States. Journal of Environmental Management 56: 35-43.
Bright, C. 1998. Life Out of Bounds: Bioinvasion in a Borderless World. W. W. Norton & Company, New York.
Carlton J. and G. Ruiz. 2000. The vectors of invasions by alien species. pp 82-89 In Preston, G., Brown, G. and E. van Wyk (eds.). Best Management Practices for Preventing and Controlling Invasive Alien Species. Symposium Proceedings. The Working for Water Programme, Cape Town.
Crosby, A. W. 1986. Ecological Imperialism: The Biological Expansion of Europe, 900-1900. Cambridge University Press, Cambridge, New York.
Dalmazzone, Silvana. 2000. Economic factors affecting vulnerability to biological invasions. Pp. 17-30 in Perrings, Charles, Mark Williamson and Silvana Dalmazzone (eds.). The Economics of Biological Invasions. Edward Elgar, Cheltenham, UK.
Daszak, P. A. A. Cunningham, and A. D. Hyatt. 2000. Emerging Infectious Diseases of Wildlife: Threats to Biodiversity and Human Health. Science. 287:443-449.
Drake, J.A., H.A. Mooney, F.D. Castri, R.H. Groves, F.J. Kruger, M. Rejmánek, and M. Williamson (eds.). Biological Invasions: A Global Perspective. Wiley and Sons, Chichester, England.
Elton, C.S. 1958. The Ecology of Invasions by Plants and Animals. J. Wiley, New York.
Ewel, John J., and 20 others. 1999. Deliberate introductions of species: research needs. BioScience 49(8):619-630.
Fairchild, W.L., E.O. Swansburg, J.T. Arsenault, and S.B. Brown. 1999. Does an Association between pesticide use and subsequent declines in catch of Atlantic salmon represent a case of endocrine disruption? Environmental Health Perspectives 107:349-358.
Foxcroft, Llewellyn C. 2001. A Case Study of Human Dimensions in Invasion and Control of Alien Plants in the Personnel Villages of Kruger National Park. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Genovesi, Piero and Sandro Bertolino. 2001. Human Dimension Aspects in Invasive Alien Species Issues: The Case of the Failure of the Grey Squirrel Eradication Project in Italy. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Gould, Steven J. 1998. An evolutionary perspective on strengths, fallacies, and confusions in the concept of native plants. Arnoldia 58(1):3-10.
Hattingh, Johan. 2001. Human Dimensions of Invasive Alien Species in Philosophical Perspective: Towards an Ethics of Conceptual Responsibility. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Hirsch, S.A. and J.A. Leitch. 1996. The Impact of Knapweed on Montana's Economy. Department of Agricultural Economics, North Dakota State University, Fargo, North Dakota, Agricultural Economics Report 355.
Hoyt, E. 1992. Conserving the Wild Relatives of Crops. IBPGR, IUCN and WWF. Second Edition.
Jenkins, Peter T. 2001. Who Should Pay? Economic Dimensions of Preventing Harmful Invasions Through International Trade and Travel. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Kowarik, I. 1990. Some responses of flora and vegetation to urbanization in Central Europe. pp. 45-74 in Sukopp, H., S. Mejny and I. Kowarik (eds.). Urban Ecology: Plants and Plant Communities in Urban Environments. SPB Academic Publishing, The Hague.
Levin, S.A. 1989. Analysis of risk for invasions and control programmes. pp.425-432. In J.A. Drake, H.A. Mooney, F. di Castri, R.H. Groves, F.J. Kruger, M. Rejmánek and M. Williamson (eds.). Biological Invasions: A Global Perspective. Scope 37. John Wiley and Sons.
Low, Tim. 2001. From Ecology to Politics: The Human Side of Alien Invasions. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Luken, James O. and John W. Thieret. 1996. Amur honeysuckle, its fall from grace. BioScience 46(1):18-24.
Mack, Richard N. 2001. Motivations and Consequences of the Human Dispersal of Plants. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Marambe, Buddhi, Channa Bambaradeniya, D.K. Pushpa Kumara, and Nirmalie Pallewatta. 2001. Human Dimensions of Invasive Alien Species in Sri Lanka. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Martin, Paul S. and Richard G. Klein (eds.). 1984. Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, AZ.
McNeely, J.A. 1999. The great reshuffling: how alien species help feed the global economy. Pp. 11-31 in Sandlund, O.T. et al. (eds.). Invasive Species and Biodiversity Management. Kluwer Academic Publishers, Dordrecht, The Netherlands.
McNeill, William H. 1976. Plagues and Peoples. Anchor Press, Garden City, N.Y.
Mooney, H.A. and Hobbs, R.J. 2000. Invasive Species in a Changing World. Island Press, Washington D.C.
Naylor, R.L. 1996. Invasions in agriculture: assessing the cost of the golden apple snail in Asia. Ambio 25:443-448.
Noemdoe, Simone. 2001. Putting People First in an Invasive Alien Clearing Programme: Working For Water Programme. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Orr, M.R. and T.B. Smith. 1998. Ecology and speciation. Trends in Evolution and Ecology 13(12):503-506.
Parker, Vivian. 2001. Listening to the Earth: A Call for Protection and Restoration of Habitats. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Perrings, C., M. Williamson, and S. Dalmazzone Cheltenham. 2000. The Economics of Biological Invasions. Edward Elger Publications, UK.
Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and economic costs of non-indigenous species in the United States. BioScience 50:53-65.
Reaser, Jamie. 2001. Invasive Alien Species Prevention and Control: The Art and Science of Managing People. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Reichard, Sarah H. 2001. Horticultural Introductions of Invasive Plant Species: A North American Perspective. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Shine, C., N. Williams, and F. Burhenne-Guilmin. 2000. Legal and Institutional Frameworks on Alien Invasive Species: A contribution to the Global Invasive Species Programme Global Strategy Document. IUCN Environmental Law Programme, Bonn, Germany.
Staples, George W. 2001. The Understorey of Human Dimensions in Biological Invasions. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Thomas, M.B. and A.J. Willis. 1998. Biocontrol: Risky but necessary? TREE 13(8):325-329.
Turpie, J. and B. Heydenrych. 2000. Economic consequences of alien infestation of the Cape Floral Kingdom's Fynbos vegetation, in Perrings, C., Williamson, M. and Dalmazzone, S. (eds) The Economics of Biological Invasions. Elgar, Cheltenham.
Udvardy, Miklos. 1969. Dynamic Zoogeography. Van Nostrand Reinhold, New York.
Vilà, Montserrat and Jordi Pujadas. 2001. Socio-Economic Parameters Influencing Plant Invasions in Europe and North Africa. In McNeely, J.A. (ed.). The Great Reshuffling: Human Dimensions of Alien Invasive Species. IUCN, Gland, Switzerland.
Waage, J.K. 1991. Biodiversity as a resource for biological control. pp. 149-163 in Hawksworth, D.L. (ed.). The Biodiversity of Micro-organisms and Invertebrates: Its Role in Sustainable Agriculture. CAB International, Oxford, UK.
Watkinson, A.R., R.P. Freckleton, and P.M. Dowling. 2000. Weed invasion of Australian farming systems: from ecology to economics, in Perrings, C., M. Williamson, and S. Dalmazzone (eds.). The Economics of Biological Invasions. Elgar, Cheltenham.
White, P. and G. Newton-Cross. 2000. An introduced disease in an invasive host: the ecology and economics of rabbit calcivirus disease (RCD) in rabbits in Australia. In Perrings, C., M. Williamson, and S. Dalmazzone (eds.). The Economics of Biological Invasions. Elgar, Cheltenham.
Williamson, M. 1998. Measuring the impact of plant invaders in Britain, in Starfinger, S., K. Edwards, I. Kowarik and M. Williamson (eds.). Plant Invasions. Ecological Mechanisms and Human Responses, Leiden, Backhuys: 57-70.
Wilson, Edward O. 1984. Biophilia. Harvard University Press, Cambridge, Massachusetts.
Zavaleta, E. 2000. Valuing ecosystem services lost to Tamarix invasion in the United States. In Mooney, H.A. and R.J. Hobbs (eds.). Invasive Species in a Changing World, Island Press, Washington, D.C.