Community-based Control of Invasive Species

By Paul Martin

Invasive species are among the greatest challenges to environmental sustainability and agricultural productivity in the world. One of the most promising approaches to managing invasive species is voluntary citizen stewardship. However, in order for control measures to be effective, private citizens often need to make sustained and sometimes burdensome commitments.

Community-Based Control of Invasive Species is based on five years of research by leading scholars in natural resource and human behavioural sciences, which involved government and citizen groups in Australia and the United States. It examines questions including, 'how can citizens be engaged in voluntarily managing invasive species?', 'what communication strategies will ensure good motivation and coordination?' and 'how can governing bodies support citizens in their efforts?'.

With chapters on institutional frameworks, changing governance, systems thinking, organisational learning, engagement, communication and behavioural change, this book will be a valuable reference for researchers and practitioners involved in natural resources management.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Jun 1, 2019
• ISBN: 9781486308897

Book preview

Preface: supporting citizen stewardship

Paul Martin

Managing invasive species is a significant social challenge. It involves securing the involvement of many people to serve many roles: conducting technical investigations; managing government funding and coordination projects; specialist advice and operations; and, with pest species that have become established in the landscape, carrying out essential frontline control activities. To be effective in frontline control often requires a sustained, and sometimes burdensome, commitment from private citizens. To secure this social investment requires good communications with the community and the ability to win the continuing engagement of many people with diverse interests – and to maintain this even when conditions are unfavourable.

Between 2012 and 2017, a large team of Australian and American researchers and frontline practitioners sought answers to questions such as:

•How can voluntary engagement by private citizens to tackle a very difficult challenge be achieved?

•What types of communication strategies will ensure strong motivation and good coordination?

•Can public and private bureaucracies be reshaped to support citizens who are prepared to do the right thing?

The aim was to provide the people working in the field of invasive species management with the best available tools to meet the social and human behaviour challenges of their work. Many collaborations between researchers, control practitioners and citizens helped to find ways to focus the ‘human sciences’ on these aspects of invasive species control. This resulted in new tools applied to many practical problems encountered by practitioners, and provided training and other supports to those working at the coalface.

The social requirements for managing invasive species are not unique to the management of invasive species. Many natural resource stewardship initiatives, such as the protection of habitats, managing water or protecting soils face similar challenges. Communities, particularly rural communities, also have to deal with the same sorts of challenges when attempting to ensure resilience in the face of many types of external threats, or to ensure the welfare of members of that community. Though this book focuses specifically on the management of invasive species, its content is relevant to many other difficult challenges.

The book also contributes at another level: political concerns are often expressed about the effectiveness and the cost of public regulation and other government policies. As a result, policy innovations are often advocated, including novel instruments, initiatives to encourage philanthropy and voluntary action, and forms of ‘smart’ regulation. Industry self-regulation, codes and standards and hybrid governance are often proposed as alternatives to policed regulation. However, implementation of any such governance paradigm requires far more than law and policy instruments, or organisational structures. It also requires suitable resourcing arrangements, ways of interacting, and skills. This book considers many of the complementary changes needed to make the policy and regulation innovations that place more emphasis on citizen action effective. The content of this book is relevant well beyond the management of invasive species.

Primarily, this book is one outcome of a fruitful Australian–US collaboration. Other outcomes include training programs and research reports, and research-based recommendations about how to better align institutions to the needs of the people who take on the important stewardship roles. The chapters in this book concern various aspects of engagement, communications, human behaviour and institutional arrangements that are likely to affect citizen action on invasive species. They complement the publications and practice support resources that were generated by the Invasive Animals Cooperative Research Centre program on facilitating effective citizen action (IACRC Program 4E). Most of the work of the IACRC Program 4E collaboration focused on Australian issues; the involvement of the US partners, particularly those from Penn State University and Cornell University provided additional expertise that enabled an accelerated research agenda and the application of their knowledge to problems that are significant in practice. Box F1 lists the principles that guided the IACRC Program 4E research and laid the foundation for the structure and chapters of this book.

Basically, the work of the researchers followed two paths: (1) develop and distribute best practice guidance, based on up-to-date research of engagement and communications – we developed publications, online tools and training to meet this aim; and (2) work with frontline teams on particular research and practice projects that practitioners nominated, thus providing a ‘real world’ set of challenges and a basis for researchers and practitioners to work together to tackle them. The Appendix provides more details on the outcomes of the project.

Box F1. IACRC Program 4E streams and principles

We structured the IACRC Program 4E into four streams: engagement, communications, institutions and integration. We agreed a set of fundamental principles (see Box 1.2) for the research and practice improvement work, and evaluated our teams’ performance against these principles using surveys and discussion. A priority was to ensure that we were delivering real value to our collaborators and to those working at the frontline.

IACRC Program 4E principles

1. Our overall aim is to support and demonstrate a community-led model of invasive species management.

2. Our priority is to deliver tangible value to the ‘clients’ who are able to use the outputs. Our research will be identified and co-developed or negotiated with the ‘client’/partner. We work ‘with’ and ‘for community, not ‘on’ community.

3. Our partners will be genuinely engaged in the research and in its translation into practice. We will blend partner team members in our research/practice teams.

4. While working through government agencies, NRM bodies, etc., our focus is enabling those ‘at the frontline’, whether government or NGO or corporate workers.

5. One measure of our success will be an active cohort of leaders and communities of practice who are skilled in contemporary approaches.

6. We aim to embed scientific ‘continuous improvement’ approach in the management of the human aspects of invasive species control, based upon sound theory, empirical testing, peer dialogue and evaluation.

It would be misleading to suggest that all aspects of the research and the collaborations went smoothly. This was never likely given these principles. Under the agreed approach, frontline partners largely determined our priorities, and these (and the design of the program as a whole) required that the researchers work closely with ‘clients’ and with people from different disciplines and institutions, often across two countries. There were some conflicts and occasional tears. Resource re-allocation was needed at various times to meet the needs prioritised through our discussions with partners. We tried things that did not work as well as we wanted, such as experimental online communities of practice. For some challenges, feasible solutions were beyond what we could do within the boundaries of time, resources and our capabilities. But overall it was very successful.

We designed the research team’s internal processes, including how we allocated our resources and our reporting, to minimise bureaucracy and to maximise flexibility to meet the needs of our clients and partners. We used annual confidential surveys of stakeholders and of the research team itself to check our progress against the criteria that we set for the program, reflecting the core principles. Confidential telephone interviews were carried out by an interviewer who was not part of the program to make it easier for people to make critical comments about the team’s work, or to put forward proposals for doing things differently. This allowed us to check that we were doing what we had promised to do, and that our stakeholders were getting value from the work. The results from the surveys showed that (as our four programs matured and outcomes became more tangible) external stakeholders became increasingly happy with what the program was delivering. They generally believed that we were true to our principles. Within the team, we were satisfied that we were making a valuable contribution and that we were true to our principles; nevertheless, we generally felt that there was more that we wanted to do.

Importantly, as well as achieving useful outcomes, we made many friendships and achieved successes. We maintained a strong sense that we were all ‘in it together’ trying to do important work that would make a real contribution to those at the frontline. Over the last 6 years, many of the authors of this book have had the privilege of working with people who do far more than their personal responsibility requires, spending many weeks each year coordinating and managing programs with their neighbours. These champions work together to form control strategies, then implement and evaluate their programs. Often citizen teams carry out frontline work on public lands over which they have no legal title and for which they have no formal responsibility – in one instance even becoming ‘feral weeders’ who sneak onto public lands to control invasive plants when the responsible agency has no staff or budget to do the necessary work. Clearly, without the substantial sacrifices made by some people, the serious problem of invasive species would be far worse than it is today

Our aim with this book is to provide future leaders who are responsible for encouraging community engagement in the management of invasive species in Australia with ideas that are relevant to their work. There are aspects of this challenge that are not obvious even to those who are involved, and this book will reveal many of these. Some of the chapters deal with abstract ideas, such as the philosophical basis of the relationship between experts and citizens; others deal with the science that underpins modern methods of communication and engagement, and still others deal with strategic questions. The purpose of this book is to expose practitioners, especially, to thinking that goes beyond the usual to better meet an increasingly difficult social, as well as ecological and economic, challenge.

At its heart, the book is based on a belief that the management of invasive species is not fundamentally a technical problem – concerned only with better ways of killing harmful species, reducing breeding rates and creating containment – but a social challenge. It requires the alignment of institutions, of public and private organisations, groups of people and individuals. This book describes the techniques and theories – adapted to fit needs – that informed the IACRC Program 4E. The chapters are a mix of theory, case studies and advice; they discuss issues that already have currency, such as ‘engagement’ and ‘social responsibility’ and ‘communication’, but they do so in ways that underline the necessity of aligning the many factors that make up effective and efficient social interactions.

Structure of the book

The book covers various aspects of the IACRC Program 4E. The first few chapters discuss the governance structures and institutions that provide the framework within which invasive species managers work and how that framework is changing and requiring innovative management. Chapter 1 outlines the governance structure and institutions in Australia and the US and how they are changing to embrace a novel policy concept, ‘shared responsibility’. The chapter discusses the impact of policy changes on frontline invasive species managers. Chapter 2 explains the method, systems thinking, used as a key framework for key aspects of this work and relates to the implementation of the policy changes to strategy discussed in Chapter 1. The systems thinking method has proven useful to help community groups and strategists to gain a clear understanding of complex problems. Chapter 2 provides examples of how some groups have used the method.

An important requirement to meet the challenges identified in Chapter 1 is for organisations to become more adaptive and to continuously learn. For any organisation, this is difficult; and it is particularly so for bureaucracies. Achieving the necessary internal coordination is also not easy but there are methods for doing so. Chapter 3 considers what it means to be an adaptive and learning organisation, providing case study examples of how some groups have managed to embed learning and adaptation in their work, and introducing concepts of engagement and communication that are explored in more depth in the book.

Chapters 5–7 reinforce some of the insights discussed in the early chapters, reframed in terms of the community engagement challenge, and placing the chapters that follow in the context of that challenge. Chapter 5 explains how today’s shared responsibility system needs to remodel the expert–citizen relationship. Chapter 6 discusses the changing role of leadership within a remodelled engagement regime. Chapter 7 further explores the concept of collective reflection as a way to stimulate continuing improvement, also considered in Chapter 3.

Chapters 9 and 10 explore how the behavioural sciences can ensure that those involved in invasive species management are more scientific and more effective in public communication. Effective responses to the complex problems of invasive species management, including the need for effective methods to shape behaviour to meet social goals, is a variant of problems faced in other professions, such as community health and education programs. There are lessons from the scientific theories and practices applied in those field that can be translated into methods for more effective social engagement in invasive species management. Chapter 8 considers the value of taking lessons from other disciplines, using a scientific approach to effectively engaging the community in the management of invasive species. Chapter 9 discusses behaviour change and how a sophisticated understanding what this entails can help with invasive species management. One method to make it more likely that communication (essential to achieve effective community engagement) is effective is to ensure that messages are precisely targeted. Chapter 10 provides methods to ‘segment’ groups in society who are involved with, or should be involved with, the management of invasive species, to ensure accurate delivery of carefully crafted communication.

The last two chapters return to the broader social and institutional framework for invasive species management. Chapter 11 focuses on the operation of the mass media: an issue identified by invasive species practitioners as increasingly significant in the governance system that affects citizen action. Chapter 12 considers what might be done to increase the effectiveness of invasive species management, given the insights from theory and practice that are available from this book and the other resources developed in IACRC Program 4E ‘Facilitating effective community action’.

Bibliography

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Cattanach G, Harris A, Horne J (2013) Mapping Australia’s Weed Management System. Rural Industries Research and Development Corporation, Canberra, <https://www.agrifutures.com.au/wp-content/uploads/publications/13-019.pdf>.

Craik W, Palmer D, Sheldrake R (2017) ‘Priorities for Australia’s biosecurity system: an independent review of the capacity of the national biosecurity system and its underpinning intergovernmental agreement’. Commonwealth of Australia, Canberra, <http://vinehealth.com.au/wp-content/uploads/2014/07/priorities-for-aus-bio-system-red.compressed.pdf>.

Foley P (2015) Fight to end fire ants chews up resources. Queensland Times, Ipswich, 18 April.

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Spring D, Keith J, Kompas T (2016) Eradicating fire ants is still possible, but we have to choose now. The Conversation, 1 December, pp. 12–15.

Verbeek M, Martin P, Fortunato M, Alter TR, Bridger J, Radhakrishna R (2016) Evaluation of a natural resource management program: an Australian case study. Australasian Journal of Environmental Management 23(4), 382–401. doi:10.1080/14486563.2016.1250680

1

A focus on citizen-led action

Paul Martin and Autumn Smith-Herron

Invasive species pose a major risk to the environment, industry and health: invasive species – pests, diseases and weeds – threaten agriculture and forestry, native species, natural regeneration and ecosystem resilience. They already have a massive environmental, social and economic impact, and climate change is likely to enable new invasive species to thrive. (Cresswell and Murphy 2016, p. v)

This quote from Australia’s 2016 State of the Environment report summarises a significant challenge: the management of the increasing harms from invasive species. Harms caused by invasive species are increasing in Australia – where it is one of the five major threats to biodiversity, and a significant cause of economic cost – and this is true around the world. As human beings move around the planet, they take with them plants, animals, viruses, fungi and single-celled protists, which including moulds and protozoa. The reasons for this movement of species include: to provide food, fibre and fuel; to recreate aesthetic or other conditions from other places; to collect and display exotic species; or to achieve environmental or production benefits. However, often the relocation of species has been accidental, such as the introduction of the black rat and the many European weeds introduced into the New World. Unfortunately, many of the introductions, whether intentional or not, have been harmful to the receiving environment or to human welfare.

The Global Invasive Species Database records invasive species from around the world: animals (364), bacteria (8), fungi (19), plants (467), protista (30) and viruses (29). Including animal diseases to the database would add a significant number of harmful invasive species. The 100 of the Worst report illustrates that invasive species have many deleterious effects, including impacts on primary production, on the environment and on human and animal welfare (Doherty et al. 2016; Early et al. 2016; Low 2017; McGeoch et al. 2011; Paini et al. 2016). Very harmful creatures can be found in every taxonomic category, including: plant diseases and parasites that reduce production or crowd out beneficial species; invasive grasses and trees; aggressive ants and other insects; and mammals such as rats and feral pigs (Lowe et al. 2000).

This chapter first considers in more detail the costs of invasive species to the economies and social welfare of Australia and the US, and then discusses the institutional issues that ‘frame’ the management of invasive species. Institutions shape roles and obligations, and what resources can be obtained; they also largely determine how (or whether) the work of citizens is coordinated and supported by government and industry. This chapter makes the point that institutional arrangements are not distinct from community action: they are part of it because of the significant impacts they have on citizen roles and obligations, resources and coordination.

Invasive species: the costs to Australia and the US

As is the case in many other parts of the world, Australia and the US have experienced inexorable increases in invasions, despite their substantial investment and efforts to manage the invasive species challenge. Table 1.1 lists the numbers of invasive species known to exist in the two countries.

Any measures of invasive species presence and impacts is imprecise because of fluctuations over time and space and the difficulties of measurement. For example, contrasting with the figures provided in in Table 1.1, Pimentel et al. (2005) estimates that 50 000 exotic species occur in the US alone. Not all introduced species cause significant harm, however, and some provide human services. Some species are important to our economy (e.g. horses, cattle, sheep, pigs, goats, deer and poultry) or be beneficial agricultural crops (e.g. maize, wheat, rice and sugarcane).

Table 1.1. Numbers of invasive species in the US and Australia.

Source: Invasive Species Database, http://www.iucngisd.org/gisd/

In Australia, invasive species have been identified as one of the three main threats to biodiversity under the National Biodiversity Strategy, prepared as part of Australia’s commitments under the Convention on Biological Diversity (National Biodiversity Strategy Review Task Group 2010). That strategy highlights community engagement as central to all forms of biodiversity protection, including invasive species management, and many programs are used to try to motivate and enable citizen action (Department of the Environment 2014).

Notwithstanding these efforts, national state of environment (SOE) reports and other studies show that Australia continues to face deteriorating invasive species conditions. The recent 2016 SOE (Cresswell and Murphy 2016, p. 8) report for Australia summarises the situation as follows:

The pressure from invasive species and pathogens continues a very high and worsening trend. Invasive plants and animals are the most frequently cited threats to species listed in the Environment Protection and Biodiversity Conservation Act 1999, and account for 12 of the 21 identified key threatening processes. Almost all states and territories note that data on the distribution and abundance of pest plants and animals, and management effectiveness for these pests are poor.

Additional to the biodiversity impacts are the economic costs of invasions. It is hard to provide an accurate figure on the total impact. A 2016 study of the revenue and control costs of weeds to Australian grain growers put this impact at A$3.32 billion (Llewellyn et al. 2016). Another study conducted by the grains industry estimates the cost of weeds to grain production exceeds A$3 billion each year, and the risk management value of biosecurity is thousands of dollars each year for each Australian farm (Hafi et al. 2015). A NSW government committee calculated the annual costs of rabbits, carp, pigs, foxes, wild dogs, goats and introduced birds in NSW at A$170 million, and a national national economic impact of A$720 million to A$1 billion (NSW Natural Resources Commission 2016). A scenario-based analysis of the costs of selected pest animals to agriculture indicates a national range of between A$416 million and A$797 million per annum (McLeod 2016). If a value for biodiversity impacts and if the risks of potential invasive species impacts was included, the economic extent of the problem would be even greater.

The types of impact in the US are similar. The reported costs associated with invasions include detection (survey) efforts, costs associated with land management practices and habitat preservation of beneficial native species. Intentional or accidentally introduced non-native species invade native communities and predate (by browsing and grazing), compete for limited ecological resources, reduce the likelihood of native tree regeneration (Tyler et al. 2006), introduce disease and parasites, hybridise, and create en vironmental chain reactions that reduce natural diversity (Temple 1990). For example, many plants introduced into the US for food, fibre or ornamental purposes have escaped and established into natural ecosystems. These are outcompeting native plant species at an alarming rate (Morse et al. 1995). The introduction of vertebrate animals into new areas is typically human related (Pimentel et al. 2005). Some of these (domestic cat Felis catus; domestic dog Canis familiaris) are pets whose feral descendants become a threat to native species such as amphibians, reptiles, birds and small mammals, and to farmed livestock.

The negative effects of invasive species on US industry, including on international trade, forestry, fisheries and power production is counted in the billions of dollars each year (Lovell and Stone 2005). A recent study by the US Weed Science Society of America indicates that, should weed control methods fail or be unavailable through legal restrictions, removal from the market or resistance, the potential economic losses of corn and soybean crops in North America could exceed US$40 billion each year. As already mentioned, the risk of invasion is accelerating because of new transport systems that help to increase trade and tourist activities (García-Llorente et al. 2008).

Institutional frameworks for citizen action

Increasing international concern about invasive species impacts is reflected in the Aichi Convention, Target 9. The ratifying countries have committed in principle that ‘[b]y 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated and measures are in place to manage pathways to prevent their introduction and establishment’ (Convention on Biological Diversity 2016).

This reflects a general understanding that invasive alien species cause significant biodiversity loss and threaten food security, human health and economic development. It is likely that, partly because of increased human travel and trade, the adverse effects of invasive species will increase regardless of policy goals or instruments. Because the methods used to control this major problem are not sufficiently effective, significant innovation is needed to get better results.

The prevention or control of invasive species harms requires action at many levels (see Fig. 1.1). The first level is to prevent additional invasive species entering an uncontaminated area or becoming established in that area. The second level is response strategies intended to eliminate unwanted species as soon as possible after they are detected. The third level is ongoing management to control the harms once species have become established in an environment. These activities each require specialised research, administration, regulation, investment and other actions. The strategies, instruments, roles and stakeholders are different for preventative biosecurity (e.g. federal government management through customs quarantine), incursion response (e.g. state and local biosecurity emergency response teams) or ongoing pest animal or weed control (e.g. regional community-based natural resource management programs).

Fig. 1.1. Generalised invasion curve.

The nature of the issues along the invasion curve dictates what roles are played by government and by community organisations. Customs and policing activities require the power of the state, and biosecurity emergency response is likely to require powers and specialised skills most likely to be found in government – though incursion responses often aim to involve industry and community groups in a government-coordinated program. Different specialisations and organisations are involved, depending on whether the risk is to human health, to farming, to animals or to the environment, with the nature of potential impacts indicating what organisations are likely to be involved. When threats are potentially economically or environmentally catastrophic or affect human health, direct government action is often required. However, when the challenge is to control established (non-catastrophic) invasions, government is likely to rely more heavily on citizens and non-government organisations. The first reason is the many practical constraints on the ability of governments to take action. Many harmful established invasive species occur across large areas, and their control requires a substantial and sustained investment of labour and resources. Governments do not have enough human and financial resources to do this, and political dynamics make it difficult to ensure ongoing investment in any public program. Theory and experience also suggest that control of established invasions is best carried out by people who are ‘on the spot’ and who are likely to be aware of what is happening in their landscape. They should be better equipped to intervene early and to minimise the harm at a lower cost than if the work is carried out by government agencies, who carry an unavoidable bureaucratic overburden and transaction costs. In times of budget constraints and increasing demands on public investment, government agencies are finding it harder to provide the funds and other resources for large ongoing programs. They are finding ways to limit that involvement, which means that the load must be picked up by the non-government sector, or it means that the work is not done and problems remain under-managed.

The institutional arrangements at each level of government also vary depending on whether the impacts are likely to be catastrophic or merely chronic, and whether the primary impact is upon the environment, human uses of the environment, or animal or human welfare. For example, detection of a serious disease that can spread rapidly and affect animals and humans will trigger a more urgent response by different types of experts than the detection of a less aggressive invasive species that will only affect non-commercial environmental interests. As a result of these and other jurisdictional and bureaucratic arrangements, the organisational arrangements for biosecurity activities are complicated. They involve both the private and public sector, many specialised activities and significant investment.

The problem of invasive species has unique characteristics, but also has similarities with other natural resource governance challenges, such as soil degradation, agro-biodiversity loss and pollution. These all demand sustained systematic work and substantial investment at a landscape scale. They all require solving social, political and economic problems (as discussed throughout this book), not just better technologies or better control methods. Without a reliable partnership between government, industry and citizens, it is impossible to deal effectively with many of these human issues. Achieving this partnership requires better ways to engage government, industry and community in a coordinated and committed program. To overcome the many barriers to sustained collaboration requires innovation in institutions, engagement methods, communications, political organisation and operational management. Doing the same things in the same ways that they have always been done is likely to lead to the same (inadequate) control outcomes, particularly when the pressures are increasing and public resources under greater pressure.

The challenge of achieving coordinated action

Invasive species, particularly animals, are hard to control. They can be mobile and rapidly breed and they can adapt. Some are intelligent, and learn how to avoid control. Control programs can be expensive, and an ill-designed strategy can cause rebound effects or make it possible for other harmful species to increase, or can cause other undesirable results. Even if a landholder is diligent on their own land, problems easily arise due to the connective systemic nature of the issues. A coordinated whole-of-landscape approach that spans land tenures is often needed to prevent re-invasion from areas where control has not yet happened. Intermittent investment, or incomplete coverage of a region can make actions ineffective and may be counterproductive.

Comprehensive control often requires that some people take on responsibilities beyond good stewardship on their own lands. A citizen’s legal obligation as a steward on their own land, or the economic incentive to control species that cost landholders’ money or cause them difficulties, may not be enough to motivate necessary work, particularly if this goes beyond the boundaries of that person’s own estate. Leading or coordinating group activities, or managing the administrative side of coordinated programs, are essential activities where the individual economic reward is particularly small compared with the effort. In addition, for some issues, such as controlling feral cats, the personal economic incentive for landholders to invest in control is small, and the difficulties are substantial. Even if citizens are motivated, the limit to the resources that they can access is often a major impediment. Overall, effective control is behaviourally complex, and essential activities can demand a lot from the people involved in many different roles.

Climate or other contingencies affect a landholders’ capacity to carry out biosecurity activities. Industry economic cycles also affect their economic capacity to maintain control, and price volatility is a common feature of agricultural enterprises (Botterill 2002; Kuehne et al. 2010). When incomes are high for grain, for example, cattle prices may be low, or wool may be in the doldrums. At any time, one group of landholders will be able to invest but another group may not. Individual landholders also have different capacities. An impoverished landholder, or one suffering from ill-health, may not have the ability to do what is required regardless of their personal motivation. Neighbourly cooperation can moderate some of these capacity problems, but major institutions are ill-equipped to accommodate individual circumstances, and inflexibility can limit the implementation of ‘nil-tenure’ approaches to control (Standing Committee on Agriculture Forestry and Fisheries and Schultz 2005).

Invasive species can also have economic or emotional significance for some people that complicates management. This may be for cultural reasons (e.g. the propagation and private trade in garden weeds), for consumption (e.g. edible, but potentially harmful, plants and animals), for recreation (such as hunting), or for economic reasons, including the illegal trade in species. A weed plant may be a much-loved garden flower or source of medicine or food. It may be propagated and spread for these reasons, helping