Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

# Massive yet grossly underestimated global costs of invasive insects

## Abstract

Insects have presented human society with some of its greatest development challenges by spreading diseases, consuming crops and damaging infrastructure. Despite the massive human and financial toll of invasive insects, cost estimates of their impacts remain sporadic, spatially incomplete and of questionable quality. Here we compile a comprehensive database of economic costs of invasive insects. Taking all reported goods and service estimates, invasive insects cost a minimum of US$70.0 billion per year globally, while associated health costs exceed US$6.9 billion per year. Total costs rise as the number of estimate increases, although many of the worst costs have already been estimated (especially those related to human health). A lack of dedicated studies, especially for reproducible goods and service estimates, implies gross underestimation of global costs. Global warming as a consequence of climate change, rising human population densities and intensifying international trade will allow these costly insects to spread into new areas, but substantial savings could be achieved by increasing surveillance, containment and public awareness.

## Introduction

For millennia, insects have been responsible for spreading devastating infectious diseases in both humans1 and livestock2, ravaging crops and food stocks3, damaging forests4, destroying infrastructure5, altering ecosystem functions6 and weakening the resilience of ecosystems to other disturbances7. This single invertebrate class (2.5 million species8) is therefore probably the costliest animal group to human society.

A global challenge this century will be meeting the world’s food requirements while maintaining economic productivity and conserving biodiversity. Globally, insect pests have been reported to reduce agricultural yields by 10–16% before harvest, and to consume a similar amount following harvest9. In fact, the largest food-producing countries, China and the United States, exhibit the highest potential losses from invasive insects10. Several other insect pests defoliate trees4 and degrade plant biodiversity, threaten commercial forestry and hamper climate change mitigation via increased tree mortality and associated increases in greenhouse-gas emissions11. Many other insects are nuisance species or disease vectors that directly erode public health—from the Seventeenth to Twentieth centuries, insect-borne diseases caused more human disease and death than all other causes combined12.

Insects are also among the most pervasive of invasive species. For example, 87% of the 2,500 non-native terrestrial invertebrates in Europe are insects13. Yet, reliable estimates of their impacts are difficult to obtain, in particular for economic assessments. Most cost estimates are disparate, regionally focused, cover variable periods and are not always grounded in verifiable data (see Methods). The types of costs also vary and include both direct and indirect components (Fig. 1). Consequently, extrapolating local costs to global scales is challenging and few have attempted to overcome the many inherent flaws in this approach.

### Validity of annual cost rate metric

It is possible that the impact rate of any invasive species will vary over time, with rates being initially low following original establishment, and then increasing as the species expands its range and possibly declining as hosts are eliminated or humans adapt to the invasion. Consequently, a simple sum of rates from many species that invaded at different points in time might not provide a practical measure of standardized costs. However, ascertaining the year of invasion of all species we examined was impossible or suspect, given a lack of monitoring data for many species. To examine the potential problem indirectly, we plotted the cost rates versus the applicable year (median or publishing year for most goods and services estimates; initial year of reporting interval for human health estimates) for the goods and services and human health estimates separately. The subsequent bivariate plots (Supplementary Fig. 1) do not reveal any relationship with time. We therefore consider the use of cost rates as an appropriate metric for standardizing costs across species, regions and time intervals.

### Determining cost estimate reproducibility

We determined the reliability of the cost estimates given in each study by identifying the source of all the figures used to extrapolate regional costs. When monetary values were based on available calculation methodologies, traceable original references and clearly identified uncertainties, we deemed the resulting final costs to be ‘reproducible’. This reproducibility is not an assessment of quality or realism of the estimation; rather, it is a qualitative assessment of whether the initial values, assumptions and methodology applied to obtain the monetary value can be fully understood (and ideally repeated). Conversely, we defined as ‘irreproducible’ any monetary values that could not be fully traced, clearly understood or justified. Thus, we deemed a monetary value to be irreproducible when it was not properly referenced, was not traceable, was derived from a potentially subjective source (for example, a personal communication or a web page with no supporting references), did not have the full details of the calculations or did not provide a clear list of the underlying assumptions. We assessed reproducibility for every monetary value we found in the literature; hence, some values might be reproducible and others irreproducible in the same study (for example, ref. 36).

We could not apply the criteria in the same way to all types of monetary values. For example, assumptions and calculations are necessary when monetary values result from extrapolations (for example, see the calculations in Table 3 of ref. 37 or the values in ref. 38), but not when they are reports of raw expenses and costs (for example, values reported in ref. 39). The attribution of reproducibility was therefore a qualitative procedure specific to each monetary value. As a consequence, we supported our choices with narrative details about each value in the database (see, for example, ‘detailed notes’ worksheet in Supplementary Data 1).

The attribution of reproducibility to monetary estimates was clear in most cases. For example, values provided in refs 28, 37, 38 were explained clearly with respect to details, methodologies, assumptions and limits; therefore, we classified them as ‘reproducible’. Conversely, values for Ae. albopictus were classified as irreproducible in ref. 6 because they were associated to a reference on Anoplophora glabripennis. Likewise, some values in ref. 7 were either non-sourced or were associated with personal communications, and were thus deemed irreproducible. However, in some cases, the attribution was less certain. For example, in several cases we were not able to obtain the sources of the estimates, especially for non-English sources; therefore, we conservatively decided to attribute irreproducibility to these (for example, the various values in ref. 8), although we acknowledge that they might in fact be reproducible. In the case of raw reports of expenses and costs, we generally classified values provided by official institutions as reproducible (for example, those in ref. 4), and from uncertain sources such as personal communications with no more details than the name (for example, those in ref. 8) or from conferences (for example, those in ref. 9) as irreproducible.

### Data availability

The authors declare that all data supporting the findings of this study are available within the article and its Supplementary Information files.

How to cite this article: Bradshaw, C. J. A. et al. Massive yet grossly underestimated global costs of invasive insects. Nat. Commun. 7, 12986 doi: 10.1038/ncomms12986 (2016).

## References

1. 1

World Health Organization. World Malaria Report 2015 World Health Organization (2015).

2. 2

Mellor, P. S., Boorman, J. & Baylis, M. Culicoides biting midges: their role as arbovirus vectors. Annu. Rev. Entomol. 45, 307–340 (2000).

3. 3

Oerke, E.-C. Crop losses to pests. J. Agric. Sci. 144, 31–43 (2006).

4. 4

Aukema, J. E. et al. Historical accumulation of nonindigenous forest pests in the continental United States. BioScience 60, 886–897 (2010).

5. 5

Su, N. Y. Novel technologies for subterranean termite control. Sociobiology 39, 95–101 (2002).

6. 6

Kenis, M. et al. Ecological effects of invasive alien insects. Biol. Invasions 11, 21–45 (2009).

7. 7

Charles, H. & Dukes, J. in Biol. Invasions. Vol. 193. Ecological Studies (ed. Wolfgang N. Ch. 13, 217–237Springer (2007).

8. 8

Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G. B. & Worm, B. How many species are there on Earth and in the ocean? PLoS Biol. 9, e1001127 (2011).

9. 9

Bebber, D. P., Ramotowski, M. A. T. & Gurr, S. J. Crop pests and pathogens move polewards in a warming world. Nat. Clim. Change 3, 985–988 (2013).

10. 10

Paini, D. R. et al. Global threat to agriculture from invasive species. Proc. Natl Acad. Sci. USA 113, 7575–7579 (2016).

11. 11

Kurz, W. A. et al. Mountain pine beetle and forest carbon feedback to climate change. Nature 452, 987–990 (2008).

12. 12

Gubler, D. J. Resurgent vector-borne diseases as a global health problem. Emerg. Infect. Dis. 4, 442–450 (1998).

13. 13

Roques, A. et al. in Handbook of Alien Species in Europe. Vol. 3. Invading Nature - Springer Series in Invasion Ecology Ch. 5, 63–79Springer (2009).

14. 14

Invasive Species Specialist Group. Global Invasive Species Databasewww.iucngisd.org/gisd/ (2015).

15. 15

Zalucki, M. P. et al. Estimating the economic cost of one of the world’s major insect pests, Plutella xylostella (Lepidoptera: Plutellidae): just how long is a piece of string? J. Econ. Entomol. 105, 1115–1129 (2012).

16. 16

Widmer, L. L., Blank, P. R., Van Herck, K., Hatz, C. & Schlagenhauf, P. Cost-effectiveness analysis of malaria chemoprophylaxis for travellers to West-Africa. BMC Infect. Dis. 10, 279–279 (2010).

17. 17

Bellard, C. & Jeschke, J. M. A spatial mismatch between invader impacts and research publications. Conserv. Biol. 30, 230–232 (2016).

18. 18

Costanza, R. et al. Changes in the global value of ecosystem services. Global Environ. Change 26, 152–158 (2014).

19. 19

Nunes, P. A. L. D. & van den Bergh, J. C. J. M. Economic valuation of biodiversity: sense or nonsense? Ecol. Econ. 39, 203–222 (2001).

20. 20

Macintyre, P. & Hellstrom, J. An Evaluation of the Costs of Pest Wasps (Vespula species) in New Zealand 1–44New Zealand Department of Conservation and Ministry for Primary Industries (2015).

21. 21

Rodriguez, L. F. Can invasive species facilitate native species? Evidence of how, when, and why these impacts occur. Biol. Invasions 8, 927–939 (2006).

22. 22

Li, D.-Z. & Pritchard, H. W. The science and economics of ex situ plant conservation. Trends Plant Sci. 14, 614–621 (2009).

23. 23

Sanguinetti, A. & Singer, R. B. Invasive bees promote high reproductive success in Andean orchids. Biol. Conserv. 175, 10–20 (2014).

24. 24

Aizen, M. A. et al. When mutualism goes bad: density-dependent impacts of introduced bees on plant reproduction. New Phytol. 204, 322–328 (2014).

25. 25

Pyšek, P. et al. Disentangling the role of environmental and human pressures on biological invasions across Europe. Proc. Natl Acad. Sci. USA 107, 12157–12162 (2010).

26. 26

Butchart, S. H. M. et al. Global biodiversity: indicators of recent declines. Science 328, 1164–1168 (2010).

27. 27

Bellard, C. et al. Will climate change promote future invasions? Glob. Change Biol. 19, 3740–3748 (2013).

28. 28

Holmes, T. P., Aukema, J. E., Von Holle, B., Liebhold, A. & Sills, E. Economic impacts of invasive species in forests. Ann. N. Y. Acad. Sci. 1162, 18–38 (2009).

29. 29

Vazquez-Prokopec, G. M., Chaves, L. F., Ritchie, S. A., Davis, J. & Kitron, U. Unforeseen costs of cutting mosquito surveillance budgets. PLoS Negl. Trop. Dis. 4, e858 (2010).

30. 30

Olson, L. J. & Roy, S. The economics of controlling a stochastic biological invasion. Am. J. Agric. Econ. 84, 1311–1316 (2002).

31. 31

Jenkins, P. T. Paying for protection from invasive species. Issues Sci. Technol. 19.1, 67–72 (2002).

32. 32

Xu, K. et al. Household catastrophic health expenditure: a multicountry analysis. Lancet 362, 111–117 (2003).

33. 33

Saraswathy Gopalan, S. & Das, A. Household economic impact of an emerging disease in terms of catastrophic out-of-pocket health care expenditure and loss of productivity: investigation of an outbreak of chikungunya in Orissa, India. J. Vector-Borne Dis. 46, 57–64 (2009).

34. 34

World Bank. World Bank Open Datadata.worldbank.org (2015).

35. 35

Juliano, S. A. & Philip Lounibos, L. Ecology of invasive mosquitoes: effects on resident species and on human health. Ecol. Lett. 8, 558–574 (2005).

36. 36

Dosdall, L. M. et al. Insect invasions of agroecosystems in the western Canadian prairies: case histories, patterns, and implications for ecosystem function. Biol. Invasions 13, 1135–1149 (2011).

37. 37

Colautti, R. I., Bailey, S. a., van Overdijk, C. D. A., Amundsen, K. & MacIsaac, H. J. Characterised and projected costs of nonindigenous species in Canada. Biol. Invasions 8, 45–59 (2006).

38. 38

Aukema, J. E. et al. Economic impacts of non-native forest insects in the continental United States. PLoS ONE 6, e24587 (2011).

39. 39

Haack, R. A., Hérard, F., Herard, F., Sun, J. & Turgeon, J. J. Managing invasive populations of Asian longhorned beetle and citrus longhorned beetle: a worldwide perspective. Annu. Rev. Entomol. 55, 521–546 (2010).

## Acknowledgements

We thank B. Geslin and F. Chiron for discussion and direction on building the database. This work is supported in part by grants from BNP-Paribas and ANR InvaCost grants, and the Australian Research Council (FT110100306).

## Author information

Authors

### Contributions

C.J.A.B. and F.C. conceived and designed the study. B.L., M.B.-M., C.A. and A.F. compiled the database. C.J.A.B. and C.B. did the analyses. C.J.A.B. and F.C. wrote the manuscript with input from all contributing authors.

### Corresponding authors

Correspondence to Corey J. A. Bradshaw or Franck Courchamp.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary Information

Supplementary Figures 1 - 9, Supplementary Table 1, Supplementary Note 1, Supplementary Methods and Supplementary References (PDF 1000 kb)

### Supplementary Data 1

Goods and services costs. List of estimates (and references) for 'goods and services' costs due to invasive non-native insects. (Microsoft Excel file; all cited articles, reports and chapters available from the authors upon request) (XLSX 95 kb)

### Supplementary Data 2

Human health costs. List of estimates (and references) for 'human health' costs due to invasive non-native insects. (Microsoft Excel file; all cited articles, reports and chapters available from the authors upon request). Outbreak frequencies derived from Supplementary Data 3. (XLSX 223 kb)

### Supplementary Data 3

Outbreak frequencies. National outbreak frequencies of disease epidemics arising from invasive insects. Years of epidemics of dengue, yellow fever, and chikungunya for 72 countries are shown to calculate outbreak frequencies (probabilities). Source: www.who.int/csr/don/archive/year/en/ (Microsoft Excel file). (XLSX 33 kb)

## Rights and permissions

Reprints and Permissions

Bradshaw, C., Leroy, B., Bellard, C. et al. Massive yet grossly underestimated global costs of invasive insects. Nat Commun 7, 12986 (2016). https://doi.org/10.1038/ncomms12986

• Accepted:

• Published:

• ### Experimental study of newly described avian malaria parasite Plasmodium (Novyella) collidatum n. sp., genetic lineage pFANTAIL01 obtained from South Asian migrant bird

• Elena Platonova
• Justė Aželytė
• Vaidas Palinauskas

Malaria Journal (2021)

• ### Evolution of Toll, Spatzle and MyD88 in insects: the problem of the Diptera bias

• Letícia Ferreira Lima
• André Quintanilha Torres
• Renata Schama

BMC Genomics (2021)

• ### Citizen science and niche modeling to track and forecast the expansion of the brown marmorated stinkbug Halyomorpha halys (Stål, 1855)

• Jean-Claude Streito
• Marguerite Chartois
• Jean-Pierre Rossi

Scientific Reports (2021)

• ### High and rising economic costs of biological invasions worldwide

• Christophe Diagne
• Boris Leroy
• Franck Courchamp

Nature (2021)

• ### Constructing regulation on assisted migration: findings from science and ethics

• Maksim Lavrik

SN Social Sciences (2021)