Research Article |
Corresponding author: Thomas Evans ( thomgevans@gmail.com ) Academic editor: Curtis Daehler
© 2020 Thomas Evans, Tim M. Blackburn, Jonathan M. Jeschke, Anna F. Probert, Sven Bacher.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Evans T, Blackburn TM, Jeschke JM, Probert AF, Bacher S (2020) Application of the Socio-Economic Impact Classification for Alien Taxa (SEICAT) to a global assessment of alien bird impacts. In: Wilson JR, Bacher S, Daehler CC, Groom QJ, Kumschick S, Lockwood JL, Robinson TB, Zengeya TA, Richardson DM. NeoBiota 62: 123-142. https://doi.org/10.3897/neobiota.62.51150
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We use a recently proposed framework, the Socio-Economic Impact Classification for Alien Taxa (SEICAT) to undertake the first global assessment of the impacts of alien birds on human well-being. A review of the published literature and online resources was undertaken to collate information on the reported socio-economic impacts of 415 bird species with self-sustaining alien populations worldwide. These data were then categorised following the SEICAT guidelines. Impact data were found for 57 (14%) of the 415 alien bird species in this study. All but two of these species were found to have minor impacts on human well-being. The most significant threat to human well-being posed by alien birds may be associated with their impacts on aviation safety. About two-thirds of the impact data found described agricultural impacts. No data were found describing disease transmission impacts on humans. We lack data for developing regions of the world: this is of concern as alien species can threaten livelihoods in developing countries, particularly by affecting agricultural production and hence food security. Most assessments were allocated a ‘Low’ confidence score. This may be because SEICAT is a new framework, requiring data on the way in which alien species affect human well-being, as measured by changes to human activities: even where we do have data describing an alien bird impact, information on how profoundly this impact affects people’s activities is currently rarely available.
Aviation safety, biological invasions, common starling, Canada goose, Eurasian blackbird, frugivory, grape damage, human well-being
The socio-economic impacts of alien species can be severe, affecting human health and livelihoods across the globe. For example, in the Mediterranean, the silver-cheeked toad-fish (Lagocephalus sceleratus) impacts commercial and recreational fishing activities by predating upon fish caught in nets and damaging fishing gear. It is also highly toxic and has little economic value, but represents 4% of the total weight of artisanal catches, resulting in reduced incomes (
While there are many examples of alien species having socio-economic impacts, systematic assessments of these impacts for a given alien higher taxon are rare. Here, we address this with an analysis of the socio-economic impacts of an entire alien taxon, birds, the alien populations of which are relatively well documented (
To date, four studies have used scoring systems to quantify the socio-economic impacts of alien birds (
The recently proposed Socio-Economic Impact Classification for Alien Taxa (SEICAT:
A list of 415 alien bird species with self-sustaining populations worldwide (i.e. established breeding populations that can persist without further human intervention) was taken from
The impact categories have been designed to reflect an increase in the order of magnitude of a particular impact caused by an alien species to human well-being. Impacts of MC do not affect human well-being; MN impacts make it difficult for people to participate in their normal activities and individuals suffer in at least one constituent of human well-being (e.g. security, material assets, health); MO impacts result in a reduction in the size of an activity, with fewer people participating in it (e.g. the partial abandonment of an activity); MR impacts result in the local disappearance of an activity from all or part of an area invaded by an alien taxon (e.g. people switch to other activities), but this impact is considered to be reversible within a decade if the alien species is controlled or removed; MV impacts result in the local disappearance of an activity and this change is likely to persist for at least a decade, even if the alien species is controlled or removed.
A series of impact descriptions were used to guide the assessment process, as shown in the Suppl. material
SEICAT does not include formal alien species impact mechanisms with which to categorise the type of impacts caused by alien species: this is because any such mechanisms are likely to vary depending on the impacting alien species and the people/communities affected. For this assessment, and based on the findings of previous studies (
Contingency table tests (unconditional exact tests: the FunChisq package (
Regional alien bird species richness scores (the number of alien bird species with established populations in a region) were calculated using the Global Avian Invasions Atlas (GAVIA:
We found 128 impact reports for 57 (14%) of the 415 bird species with self-sustaining alien populations worldwide (see Suppl. material
The number of alien bird species with recorded socio-economic impacts from each of six orders. Pas: Passeriformes; Psi: Psittaciformes; Gal: Galliformes; Ans: Anseriformes; Col: Columbiformes; Fal: Falconiformes. Total species with impacts = 57. A further 358 species were categorised as being Data Deficient (DD) under SEICAT. % = proportion of bird species in each order with impact data.
Contingency table (unconditional exact test) showing actual and expected numbers of alien bird species that have or do not have reported socio-economic impacts that also have or do not have reported environmental impacts. Expected values are displayed in italics.
Alien bird species with reported environmental impacts | Alien bird species without reported environmental impacts (DD species) | Total | |
---|---|---|---|
Alien bird species with reported socio-economic impacts | 45 | 12 | 57 |
16.34 | 40.66 | ||
Alien bird species without reported socio-economic impacts (DD species) | 74 | 284 | 358 |
102.66 | 255.35 | ||
Total | 119 | 296 | 415 |
Several alien bird species were found to have equally severe impacts through more than one impact mechanism: for example, the Canada goose consumes crops, fouls public parks and poses a risk to aviation safety. The majority (98%) of the impacts reported were classified as being ‘less severe’ (MC impacts = 9; MN impacts = 117), with the remainder being classified as ‘more severe’ (MO impacts = 2; MR and MV impacts = 0) (Figure
Impacts on agriculture was the most frequently reported impact mechanism (83 impact reports, 65% of all reported impacts), followed by damage to public facilities, buildings and utilities (26 impacts, 20%) (Figure
Contingency table (unconditional exact test) showing actual and expected numbers of impact allocations to each impact mechanism for each order of alien birds. Expected values are displayed in italics. Data for impacts by Falconiformes and disease transmission were removed from the dataset for the test, due to low sample sizes (one MN impact each).
Damage to agriculture | Damage to public facilities, buildings and utilities | Nuisance | Aviation safety | Total | |
---|---|---|---|---|---|
Passeriformes | 38 | 3 | 5 | 1 | 47 |
30.59 | 9.7 | 5.22 | 1.49 | ||
Psittaciformes | 12 | 12 | 5 | 2 | 31 |
20.17 | 6.4 | 3.44 | 0.98 | ||
Galliformes | 12 | 1 | 2 | 0 | 15 |
9.76 | 3.1 | 1.67 | 0.48 | ||
Anseriformes | 10 | 8 | 2 | 1 | 21 |
13.67 | 4.33 | 2.33 | 0.67 | ||
Columbiformes | 10 | 2 | 0 | 0 | 12 |
7.81 | 2.48 | 1.33 | 0.38 | ||
Total | 82 | 26 | 14 | 4 | 126 |
The greatest number of impacts were recorded in Australasia (48 impacts, 38% of all impacts), followed by Oceanic Islands (26 impacts, 20%). No impact data were found for South America (Figure
The severity and type of socio-economic impacts caused by alien birds, and the regions in which they are sustained. This figure shows the number of impact records for each of: (A) five impact categories; (B) six impact mechanisms; and (C) seven regions of the world. MC: Minimal Concern; MN: Minor; MO: Moderate; MR: Major; MV: Massive. Agr: Damage to agriculture; Fac: Damage to public facilities, buildings and utilities; Nui: public nuisance; Avi: risk to aviation safety; Dis A: transmission of diseases to animals; Dis H: transmission of diseases to humans. Aus: Australasia; Isl: Oceanic Islands; Eur: Europe; N Am: North (and Central) America; Asi: Asia; Afr: Africa; S Am: South America. Total impact reports = 128.
Contingency table (unconditional exact test) showing actual and expected numbers of impact reports and regional alien species richness scores. Expected values are displayed in italics.
No. of alien bird species (alien species richness) | No. of impact reports | Total | |
---|---|---|---|
Africa | 50 | 7 | 57 |
48.48 | 8.52 | ||
Asia | 121 | 11 | 132 |
112.26 | 19.74 | ||
Australasia | 99 | 48 | 147 |
125.02 | 21.98 | ||
Europe | 112 | 20 | 132 |
112.26 | 19.74 | ||
North and Central America | 156 | 16 | 172 |
146.28 | 25.72 | ||
Oceanic Islands | 190 | 26 | 216 |
183.7 | 32.3 | ||
Total | 728 | 128 | 856 |
The majority of recorded impacts were allocated a ‘Low’ confidence score (121 impacts, 95% of all impacts); five impacts were allocated a ‘Medium’ confidence score and two were allocated a ‘High’ confidence score. Confidence scores are randomly distributed across impact mechanisms (unconditional exact test: chi-square value = 1.7, degrees of freedom = 6, P = 0.86, estimate = 0.082) (Suppl. material
As far as we are aware, this study represents the first global assessment of the socio-economic impacts of alien birds. Our literature search identified data on socio-economic impacts for just 14% of the 415 alien bird species with self-sustaining populations worldwide. This paucity of impact data reflects the findings of other studies on the socio-economic impacts of alien species, including SEICAT assessments undertaken for amphibians (
There are at least four reasons why we may lack data on the socio-economic impacts of alien birds. First, some species may have, or be perceived to have, socio-economic impacts that are minor and do not cause problems for human beings, and hence do not warrant socio-economic impact research. Research on the environmental impacts of alien species tends to focus on species that have the most damaging environmental impacts (
Second, the impacts of some species may be going unnoticed because they occur in regions of the world with limited capacity to study their impacts or in remote regions where those impacts are not easily recorded. Consistent with this hypothesis, we find more data on the socio-economic impacts of alien birds in developed regions: 66% of impacts occur in Australasia, Europe and North America; 14% occur in Asia and Africa; no impact data were found for South America (Figure
Third, the tendency for impacts to be recorded in developed regions may also reflect the global distribution of alien bird species, which tends to show high species richness in Europe, former European colonies such as the USA, Australia and New Zealand, and economic hotspots such as Singapore, Hong Kong and Taiwan (
Fourth, research on socio-economic impacts may be biased towards species with existing environmental impacts. Of the 57 alien bird species with reported socio-economic impacts, approximately 80% (45) also have reported environmental impacts; of the 358 species that are DD for socio-economic impacts, approximately 80% (284) are also DD for environmental impacts (Table
The socio-economic impacts of alien birds are generally minor (Figure
The prevalence of MC and MN impacts may support our hypothesis that we lack impact data for many alien bird species because their socio-economic impacts are negligible and do not attract research. However, a ‘Low’ confidence score was assigned to 95% of SEICAT alien bird impact assessments because, whilst adequate data were available to ascertain that an alien bird was exerting an impact, there were inadequate data to determine how severely this impact affected human well-being (in particular, to distinguish between an MN impact (where an alien bird makes an activity difficult) and an MO impact (where it causes a decline in the population participating in an activity)). This may be because whilst these studies identified socio-economic impacts, they did not go on to quantify how they affected the scale of the impacted activities. For example, by eating rice grown for duck feed, the Eurasian tree sparrow (Passer montanus) causes economic losses for duck farmers in the Philippines (
From the data that are currently available, the most severe impacts on human well-being caused by alien birds are associated with aviation safety (an air strike with a flock of common starlings having caused the deadliest bird-induced plane crash in history (
Impacts on agriculture account for approximately two-thirds of all recorded impacts (Figure
There are few data on the spread of diseases by alien birds and the subsequent socio-economic impacts (Figure
We have more confidence in the accuracy of SEICAT assessments where the impacts on human well-being are more severe (Suppl. material
This study represents the first large-scale application of the SEICAT protocol, and the first global assessment of the socio-economic impacts of alien birds. It demonstrates that SEICAT can be used effectively to quantify and categorise the impacts of alien species on human well-being. The most significant problem encountered during this assessment was a lack of impact data: we only know about the socio-economic impacts of a small proportion of the alien birds with self-sustaining populations worldwide. This study may therefore help to focus research regarding the impacts of alien birds on human well-being, particularly in developing regions of the world, where impact data are scarce. Birds are well-studied in comparison to many other taxonomic groups, and thus the problem of data paucity may extend to SEICAT assessments for other groups yet to be assessed, such as invertebrates. Nevertheless, completion of these assessments would reveal the global taxonomic distribution of impact data availability (see
SEICAT is a new framework, requiring data on the way in which alien species affect human well-being, as measured by changes to human activities: even where we do have data describing an alien bird impact, data on how profoundly this impact affects people’s activities are often unavailable. As a result, the confidence assigned to most SEICAT classifications is ‘Low’. The adoption of SEICAT may encourage a more holistic approach to future socio-economic impact assessments which not only describe impacts, but also consider their wider implications for human well-being.
T.E. is supported by the Alexander von Humboldt Foundation. A.F.P. and S.B. are supported by the Swiss National Science Foundation (grant number 31003A_179491); S.B. and J.M.J. are supported by the Belmont Forum – BiodivERsA International joint call project InvasiBES (PCI2018-092939, BMBF grant 01LC1803A); and S.B. by the Swiss National Science Foundation (grant number 31BD30_184114).
This paper was presented at a workshop on ‘Frameworks used in Invasion Science’ hosted by the DSI-NRF Centre of Excellence for Invasion Biology in Stellenbosch, South Africa, 11–13 November 2019, that was supported by the National Research Foundation of South Africa and Stellenbosch University.
Appendix A
Data type: (measurement/occurrence/multimedia/etc.)
Explanation note: Alien bird SEICAT assessment: literature review protocol.
Appendix B
Data type: (measurement/occurrence/multimedia/etc.)
Explanation note: Alien bird SEICAT assessment (species summary).
Nine additional tables
Data type: Tables
Explanation note: Table S1. Impact descriptions used to guide the SEICAT assessment process (from