This paper reviewed the benefits and negative impacts of alien species that are currently listed in the Alien and Invasive Species Regulations of the
Specifically, it identified conflict-generating species, evaluated the causes and driving forces of these conflicts and assessed how the conflicts have affected management.
A simple scoring system was used to classify the alien species according to their relative degree of benefits and negative impacts. Conflict-generating species were then identified and further evaluated using an integrated cognitive hierarchy theory and risk perception framework to identify the value systems (intrinsic and economic) and risk perceptions associated with each conflict.
A total of 552 alien species were assessed. Most of the species were classified as inconsequential (55%) or destructive (29%). Beneficial (10%) and conflict-generating (6%) species made a minor contribution. The majority (46%) of the conflict cases were associated with more than one value system or both values and risk perception. The other conflicts cases were based on intrinsic (40%) and utilitarian (14%) value systems.
Conflicts based on value and risk perceptions are inherently difficult to resolve because authorities need to balance the needs of different stakeholders while meeting the mandate of conserving the environment, ecosystem services and human well-being. This paper uses the identified conflict-generating species to highlight the challenges and trade-offs of managing invasive species in South Africa.
South Africa has a long history of alien species introductions and interventions for managing biological invasions (Richardson et al.
The main legislative instrument that guides the management of alien species in South Africa is the
The benefits and negative impacts of alien species vary widely in type and magnitude and are dependent on the species, their invasive potential, the extent to which they have invaded, the nature of the invaded environment and socio-economic contexts (Kueffer
A conceptual framework to categorise alien and invasive species based on their relative environmental and socio-economic negative impacts and benefits.
This paper, focusing on conflict-generating species, is directly aligned to one of the tenets of this special issue of
The 549 alien species that are currently listed in the A&IS Regulations (2014) were classified as inconsequential, beneficial, destructive or conflict-generating species according to their relative degree of benefits and negative impacts (Online Appendix). Three additional contentious species that are either not listed or were removed from the A&IS Regulations (2014) to avoid conflicts were also classified. Species were classified through a simple scoring system (
The scoring system used to identify conflict-generating species on the list of the alien species in the Alien and Invasive Species Regulations of 2014.
Impacts | Category | Score levels |
---|---|---|
Negative impacts | Ecological impacts | |
Socio-economic impacts | ||
Benefits | Economic benefits | |
Intrinsic benefits | ||
The identified conflict-generating species were then evaluated using an integrated cognitive hierarchy theory – risk perception framework (Estévez et al.
A conceptual framework created by integrating cognitive hierarchy theory (CHT) and risk perception theories.
Eight fundamental values that humans associate with nature.
Conflict level | Value or heuristic rule | Definition |
---|---|---|
Value system | Naturalistic | Exploration of nature and outdoor recreation |
Aesthetic | Physical attraction and appeal of nature | |
Dominionistic | Mastery and control over nature | |
Humanistic | Emotional, spiritual, or symbolic affection for nature | |
Moralistic | Moral concern about the right and treatment of nature | |
Negativistic | Fear or aversion towards nature | |
Scientific | Systematic and empirical study of nature | |
Utilitarian | Practical value or material benefit of nature | |
Risk perception | Evaluation of potentials | Differences in evaluations of potential hazards |
Lack of institutional trust | Lack of trust between stakeholders and government agencies could result from lack of community engagement and transparencies in decision making processes, differences in evaluations of potential hazards, and lack of confidence in government authorities |
Most of the 552 assessed alien species were classified as either inconsequential (55%) or destructive (29%). Far fewer species were classified as beneficial (10%) and conflict-generating species (6%) (
Categorisation of alien species listed under the A&IS Regulation (2014) based on the degree of their negative impacts (ecological and socio-economic) and benefits (economic and intrinsic). Jitter was used to indicate the density of dots where there is overlap.
Beneficial species comprised 13 animal and 42 plant species that had a score ≤ 5 for negative impacts but > 5 for benefits (
Conflict-generating species consisted of 9 animal and 25 plant species that had a score > 5 for either negative impacts or benefits (
The majority (46%) of the conflict cases could be explained by more than one conflict type and cognitive level (
Conflict-generating invasive species showing the negative impacts (ecological and social-economic), benefits (economic and intrinsic), cognitive level (VS = value system and PB = perceptions based) and value system or heuristic rule at which conflicts occurred.
Descriptive category | Common name | Species | Taxon | Costs | Benefits | Conflict level | Value or heuristic rule | ||
---|---|---|---|---|---|---|---|---|---|
Ecological | Social-economic | Economic | Intrinsic | ||||||
Leucaena | P | 7 | 7 | 6 | 5 | VS | Utilitarian | ||
Mission prickly pear | P | 6 | 6 | 8 | 4 | VS | Utilitarian | ||
Blue-leaf cactus | P | 6 | 6 | 7 | 4 | VS | Utilitarian | ||
Honey mesquite | P | 9 | 9 | 8 | 6 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Velvet mesquite | P | 9 | 9 | 8 | 6 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Guava | P | 6 | 4 | 9 | 6 | VS | Aesthetic, utilitarian | ||
Smallmouth bass | FV | 9 | 2 | 9 | 9 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Largemouth bass | FV | 8 | 2 | 9 | 9 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Brown trout | FV | 8 | 2 | 9 | 1 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Marron | I | 6 | 3 | 6 | 1 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Japanese oyster | I | 6 | 4 | 7 | 1 | VS | Utilitarian | ||
Nile tilapia | FV | 8 | 2 | 7 | 1 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Rainbow trout | FV | 8 | 2 | 9 | 1 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Golden wattle | P | 6 | 3 | 1 | 6 | VS | Aesthetic, naturalistic | ||
Red eye/rooikrans | P | 10 | 7 | 6 | 3 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Silver wattle | P | 10 | 7 | 6 | 3 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Black wattle | P | 10 | 7 | 9 | 4 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Australian blackwood | P | 10 | 7 | 7 | 5 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Slash pine | P | 8 | 4 | 8 | 5 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Patula pine | P | 8 | 3 | 10 | 4 | VS, PB | Utilitarian, evaluation of potential hazard | ||
Monterey pine | P | 8 | 3 | 8 | 6 | VS | Aesthetic, naturalistic, utilitarian | ||
Marram grass | P | 7 | 6 | 6 | 2 | VS | Utilitarian | ||
Domestic cat | TV | 7 | 5 | 1 | 8 | VS | Aesthetic, moralistic | ||
Himalayan tahr | TV | 6 | 3 | 1 | 6 | VS | Humanistic | ||
Chain-fruit cholla | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Boxing-glove cactus | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Imbricate cactus | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Pencil cactus | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Pink-flowered sheathed cholla | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Cane cholla | P | 7 | 8 | 4 | 6 | VS | Aesthetic | ||
Syringa | P | 6 | 1 | 2 | 8 | VS | Aesthetic | ||
Yellow bunny-ears | P | 6 | 6 | 3 | 7 | VS | Aesthetic | ||
Jerusalem thorn | P | 7 | 7 | 3 | 6 | VS | Aesthetic | ||
Belhambra | P | 8 | 4 | 2 | 6 | VS | Aesthetic | ||
Pink tamarisk | P | 7 | 7 | 2 | 6 | VS | Aesthetic |
Species were grouped into four descriptive taxon categories were
Conflicts centred on intrinsic value systems collectively accounted for 40% of all the examined cases of conflict-generating species (
The negative impacts and benefits framework indicated that almost half of the 552 assessed species could be classified as ‘inconsequential species’ that have neither substantial benefits nor negative impacts. Most of these inconsequential species have either limited distribution or no known impacts in South Africa or elsewhere in the world. For example, freshwater fish can only spread within a river system and their spread across the country is facilitated by human movement. Some of the species such as
Species that were classified as destructive (no substantial benefits but high negative impact) made up the second largest proportion of all the listed species on the A&IS Regulations. Species in this category are largely regarded as pests and weeds because of the deleterious effect they have on society and the environment. Many of these species were also accidental introductions. As a result, the degree of social contestation regarding ways to control or eradicate them is low. For example, there has been little public resistance to the management of invasive rodents (
There are also some species that were categorised as beneficial but not harmful. This suggests that active management is not necessary or should only be done in particular cases. Some of these perceived beneficial species still create conflict even though there is not much evidence of negative impacts and represent some unique cases. Previous attempts to manage these unique cases have led to some controversy where either proposed management actions have been completely put aside or there have been some trade-offs and compromises. For example,
Similar compromises have also been made for other listed plants that have high economic and intrinsic values, such as eucalypts (
Examples of beneficial animal species where compromises had to be made for their management include rock doves (
Actual and potential conflict-generating species made up the smallest proportion (6%) of all listed species. Species in this category had both benefits and negative impacts. The majority of these conflicts could be explained by more than one cognitive level, such as utilitarian values based on practical or material benefits and risk perceptions of possible impacts from invasive species. Examples include
Similarly,
The aversion of possible impacts of invasive species with utilitarian values is clearly illustrated by conflict around the proposed regulation of
The utilisation of
In some cases, species were associated with different conflict types that could be either intrinsic or utilitarian values. For example, the removal of invasive trees in urban or peri-urban environments in the City of Cape Town created conflicts because of the intrinsic and utilitarian values attached to certain species such as acacias, eucalypts and pines (Gaertner et al.
Conflicts centred on intrinsic values represented some form of emotional relationship between society and nature. The detected value systems included naturalistic, humanistic, aesthetic and moralistic values systems. For example, moralistic values are centred on the right of invasive animals to live and not to be abused. Control measures often involve culling which is strongly opposed by some sectors of society such as animal rights organisations (Bremner & Park
Conflicts based on utilitarian values were observed for species that are economically important because they provide food and raw materials for industry and local communities. For example, many cactus species were introduced as part of agricultural initiatives to improve fruit production for human consumption, fodder for livestock and ornamental purposes (Novoa et al.
Species that are on the margins (i.e. scoring high on the benefits) but medium on the negative impacts (and vice versa) should be prioritised for directed research as they represent areas where new conflicts might emerge. For example,
Most conflicts around the management of invasive species in South Africa could be explained by more than one value system (intrinsic vs. utilitarian) and cognitive level (values systems vs. risk perception). Value-based conflicts are inherently difficult to resolve because management authorities have to balance the needs of different stakeholders while still conserving the environment. An ideal management plan is where parties with different value systems agree on a win-win solution where invasive species can still deliver benefits, but adverse impacts are reduced. This is potentially possible through open dialogue among stakeholders, trade-offs and compromises. In cases where the perceived benefits outweigh impacts such as those observed for most of the intrinsic-based conflicts, the management approach has generally been to tolerate the species and monitor whether they potentially cause impacts in the future. In contrast, when the impacts outweigh perceived benefits, management options have involved trade-offs and compromises that have minimised impact of the invasive species but retained a large proportion of their amenity values. In extreme cases, control efforts have proceeded despite opposition because of a strong body of scientific evidence and political support. Conflicts based on risk perception were mainly centred on the fear and aversion of impacts of the invasive species or the control methods proposed for it management. In some cases, such as the use of biological agents to control invasive plants species, management authorities have employed strategies to try and effectively communicate the risks through open dialogue among stakeholders and this has resulted in trade-offs and compromises (Zachariades et al.
The majority of invasive alien species listed in the A&IS Regulations were not considered to be conflict-generating. However, the small proportion of species identified as conflict-generating hold the potential to negatively impact the future efficiency of conservation management in South Africa by forcing regulators and managers to spend great amounts of time and resources addressing stakeholder complaints and concerns instead of discharging their duties in dealing with the species that do not generate controversy. The initial delay in promulgating the lists because of the objections of the trout lobby, and the subsequent amount of time and energy spent by the Department of Environmental Affairs (DEA) staff in negotiating the relisting of trout (Woodford et al.
A.N., D.M.R., R.T.S. and B.W.vW. acknowledge funding from the DST-NRF Centre of Excellence for Invasion Biology. D.M.R. (grant 85417), B.W.vW (84512), O.L.F.W. (77444), D.J.W. (103581) and T.Z. (103602) received support from the National Research Foundation. A.N. and P.I. acknowledge funding provided by the Working for Water Programme of the South African Department of Environmental Affairs, through the South African National Biodiversity Institute Invasive Species Programme.
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
All authors collected data (scored species) and T.Z. analysed the data. R.T.S. developed the scoring framework. T.Z. drafted the manuscript with input from all other authors.