Recent reports of dramatic declines in insect abundance suggest grave consequences for global ecosystems and human society. Most evidence comes from Europe, however, leaving uncertainty about insect population trends worldwide. We used >5,300 time series for insects and other arthropods, collected over 4–36 years at monitoring sites representing 68 different natural and managed areas, to search for evidence of declines across the United States. Some taxa and sites showed decreases in abundance and diversity while others increased or were unchanged, yielding net abundance and biodiversity trends generally indistinguishable from zero. This lack of overall increase or decline was consistent across arthropod feeding groups and was similar for heavily disturbed versus relatively natural sites. The apparent robustness of US arthropod populations is reassuring. Yet, this result does not diminish the need for continued monitoring and could mask subtler changes in species composition that nonetheless endanger insect-provided ecosystem services.
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data supporting the findings of this study (curated arthropod abundances and estimated time trends) are available at the Dryad Data Repository (https://doi.org/10.5061/dryad.cc2fqz645).
The R code used to curate and analyse data are available at the Dryad Data Repository (https://doi.org/10.5061/dryad.cc2fqz645).
Price, P. W., Denno, R. F., Eubanks, M. D., Finke, D. L. & Kaplan, I. Insect Ecology: Behavior, Populations and Communities (Cambridge Univ. Press, 2011).
Watanabe, M. E. Pollination worries rise as honey bees decline. Science 265, 1170–1170 (1994).
Soroye, P., Newbold, T. & Kerr, J. Climate change contributes to widespread declines among bumble bees across continents. Science 367, 685–688 (2020).
Mathiasson, M. E. & Rehan, S. M. Status changes in the wild bees of north-eastern North America over 125 years revealed through museum specimens. Insect Conserv. Divers. 12, 278–288 (2019).
Powney, G. D. Widespread losses of pollinating insects in Britain. Nat. Commun. 10, 1018 (2019).
Fox, R. The decline of moths in Great Britain: a review of possible causes. Insect Conserv. Divers. 6, 5–19 (2013).
Casey, L. M., Rebelo, H., Rotheray, E. & Goulson, D. Evidence for habitat and climatic specializations driving the long-term distribution trends of UK and Irish bumblebees. Divers. Distrib. 21, 864–875 (2015).
Hallmann, C. A. et al. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12, e0185809 (2017).
Leather, S. R. “Ecological armageddon”–more evidence for the drastic decline in insect numbers. Ann. Appl. Biol. 172, 1–3 (2018).
Habel, J. C., Samways, M. J. & Schmitt, T. Mitigating the precipitous decline of terrestrial European insects: Requirements for a new strategy. Biodivers. Conserv. 28, 1343–1360 (2019).
Sánchez-Bayo, F. & Wyckhuys, K. A. G. Worldwide decline of the entomofauna: a review of its drivers. Biol. Conserv. 232, 8–27 (2019).
Seibold, S. et al. Arthropod decline in grasslands and forests is associated with drivers at landscape level. Nature 574, 671–674 (2019).
Salcido, D. M., Forister, M. L., Garcia Lopez, H. & Dyer, L. A. Loss of dominant caterpillar genera in a protected tropical forest. Sci. Rep. 10, 422 (2020).
Wagner, D. L. Insect declines in the Anthropocene. Annu. Rev. Entomol. 65, 457–480 (2020).
Wesner, J. S. et al. Loss of potential aquatic–terrestrial subsidies along the Missouri River floodplain. Ecosystems 23, 111–123 (2020).
Wepprich, T., Adrion, J. R., Ries, L., Wiedmann, J. & Haddad, N. M. Butterfly abundance declines over 20 years of systematic monitoring in Ohio, USA. PLoS ONE 14, e0216270 (2019).
Welti, E. A. R., Roeder, K. A., de Beurs, K. M., Joern, A. & Kaspari, M. Nutrient dilution and climate cycles underlie declines in a dominant insect herbivore. Proc. Natl Acad. Sci. USA 117, 7271–7275 (2020).
Montgomery, G. A. et al. Is the insect apocalypse upon us? How to find out. Biol. Conserv. 241, 108327 (2020).
Saunders, M. E., Janes, J. K. & O’Hanlon, J. C. Moving on from the insect apocalypse narrative: engaging with evidence-based insect conservation. Bioscience 70, 80–89 (2020).
Thomas, C. D., Jones, T. H. & Hartley, S. E. “Insectageddon”: a call for more robust data and rigorous analyses. Glob. Change Biol. 25, 1891–1892 (2019).
Outhwaite, C. L., Gregory, R. D., Chandler, R. E., Collen, B. & Isaac, N. J. B. Complex long-term biodiversity change among invertebrates, bryophytes and lichens. Nat. Ecol. Evol. 4, 384–392 (2020).
Macgregor, C. J., Williams, J. H., Bell, J. R. & Thomas, C. D. Moth biomass increases and decreases over 50 years in Britain. Nat. Ecol. Evol. 3, 1645–1649 (2019).
Gonzalez, A. et al. Estimating local biodiversity change: a critique of papers claiming no net loss of local diversity. Ecology 97, 1949–1960 (2016).
Vellend, M. et al. Estimates of local biodiversity change over time stand up to scrutiny. Ecology 98, 583–590 (2016).
van Klink, R. et al. Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances. Science 368, 417–420 (2020).
Ellis, E. C. Anthropogenic transformation of the terrestrial biosphere. Phil. Trans. R. Soc. A 369, 1010–1035 (2011).
Vitousek, P. M., Mooney, H. A., Lubchenco, J. & Melillo, J. M. Human domination of Earth’s ecosystems. Science 277, 494–499 (1997).
Kanakidou, M. et al. Past, present, and future atmospheric nitrogen deposition. J. Atmos. Sci. 73, 2039–2047 (2016).
Dornelas, M. et al. A balance of winners and losers in the Anthropocene. Ecol. Lett. 22, 847–854 (2019).
Tylianakis, J. M., Tscharntke, T. & Lewis, O. T. Habitat modification alters the structure of tropical host–parasitoid food webs. Nature 445, 202–205 (2007).
Finke, D. L. & Snyder, W. E. Niche partitioning increases resource exploitation by diverse communities. Science 321, 1488–1490 (2008).
Crowder, D. W., Northfield, T. D., Strand, M. R. & Snyder, W. E. Organic agriculture promotes evenness and natural pest control. Nature 466, 109–112 (2010).
Mack, R. N. et al. Biotic invasions: causes, epidemiology, global consequences, and control. Ecol. Appl. 10, 689–710 (2000).
Sikes, D. S. & Raithel, C. J. A review of hypotheses of decline of the endangered American burying beetle (Silphidae: Nicrophorus americanus Olivier). J. Insect Conserv. 6, 103–113 (2002).
Harmon, J. P., Stephens, E. & Losey, J. The decline of native coccinellids (Coleoptera: Coccinellidae) in the United States and Canada. J. Insect Conserv. 11, 85–94 (2007).
Agrawal, A. A. & Inamine, H. Mechanisms behind the monarch’s decline. Science 360, 1294–1296 (2018).
Garibaldi, L. A. et al. Wild pollinators enhance fruit set of crops regardless of honey bee abundance. Science 340, 1608–1611 (2013).
Samson, F. & Knopf, F. Prairie conservation in North America. Bioscience 44, 418–421 (1994).
Ratajczak, Z. et al. Abrupt change in ecological systems: inference and diagnosis. Trends Ecol. Evol. 33, 513–526 (2018).
Ives, A. R., Einarsson, Á., Jansen, V. A. A. & Gardarsson, A. High-amplitude fluctuations and alternative dynamical states of midges in Lake Myvatn. Nature 452, 84–87 (2008).
Spatiotemporal Design (NEON, National Science Foundation – National Ecological Observatory Network, 2019); https://www.neonscience.org/about/about/spatiotemporal-design
North American Butterfly Count Circles (NABA, North American Butterfly Association, 2019); https://www.naba.org/butter_counts.html
Burkle, L. A., Marlin, J. C. & Knight, T. M. Plant–pollinator interactions over 120 years: loss of species, co-occurrence, and function. Science 340, 1611–1615 (2013).
Harvey, J. A. et al. International scientists formulate a roadmap for insect conservation and recovery. Nat. Ecol. Evol. 4, 174–176 (2020).
Cardinale, B. J. et al. Biodiversity loss and its impact on humanity. Nature 486, 59–67 (2012).
Vellend, M. et al. Global meta-analysis reveals no net change in local-scale plant biodiversity over time. Proc. Natl Acad. Sci. USA 110, 19456–19459 (2013).
Dornelas, M. et al. Assemblage time series reveal biodiversity change but not systematic loss. Science 344, 296–299 (2014).
Newbold, T. et al. Global effects of land use on local terrestrial biodiversity. Nature 520, 45–50 (2015).
Lagos-Kutz, D. et al. The soybean aphid suction trap network: sampling the aerobiological “soup”. Am. Entomol. 66, 48–55 (2020).
R Core Team R: A Language and Environment for Statistical Computing (R Foundation for Statistical Computing, 2019).
De Graaf, R. M., Tilghman, N. G. & Anderson, S. H. Foraging guilds of North American birds. Environ. Manag. 9, 493–536 (1985).
Ives, A. R., Abbott, K. C. & Ziebarth, N. L. Analysis of ecological time series with ARMA(p, q) models. Ecology 91, 858–871 (2010).
Breiman, L. Random forests. Mach. Learn. 45, 5–32 (2001).
Fick, S. E. & Hijmans, R. J. WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas. Int. J. Climatol. 37, 4302–4315 (2017).
Venter, O. et al. Global terrestrial human footprint maps for 1993 and 2009. Sci. Data 3, 160067 (2016).
Halpern, B. S. et al. A global map of human impact on marine ecosystems. Science 319, 948–952 (2008).
Cutler, D. R. et al. Random forests for classification in ecology. Ecology 88, 2783–2792 (2007).
Oksanen, J. et al. vegan: Community Ecology Package. R package version 2.5-4 (2019).
Jaccard, P. The distribution of the flora in the alpine zone. N. Phytol. 11, 37–50 (1912).
Harrison, S., Ross, S. J. & Lawton, J. H. Beta diversity on geographic gradients in Britain. J. Anim. Ecol. 61, 151–158 (1992).
Barwell, L. J., Isaac, N. J. B. & Kunin, W. E. Measuring β-diversity with species abundance data. J. Anim. Ecol. 84, 1112–1122 (2015).
Koleff, P., Gaston, K. J. & Lennon, J. J. Measuring beta diversity for presence–absence data. J. Anim. Ecol. 72, 367–382 (2003).
A. R. Ives (University of Wisconsin-Madison) provided invaluable advice on our analyses, and M. R. Strand (University of Georgia) and W. F. Fagan (University of Maryland) made suggestions to improve the paper. We acknowledge funding from USDA-NIFA-OREI 2015-51300-24155 and USDA-NIFA-SCRI 2015-51181-24292 to W.E.S.
The authors declare no competing interests.
Peer review information Peer reviewer reports are available.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
(a) herbivores, (b) carnivores, (c) omnivores, (d) detritivores, (e) parasites, and (f) parasitoids. Right panels depict average change in diversity metrics and 95% confidence intervals among LTERs. Blue shading and font indicate LTER sites reporting aquatic taxa.
Boxplots depict medians (thick line), 25th and 75th percentiles (box edges), 95th percentiles (whiskers), and outliers (circles).
Abundance trends of all taxa under (a) moderate vs. relaxed time series filtering criteria and (b) strict vs. moderate filtering criteria. (c) Boxplots of abundance trends under relaxed, moderate, and strict timer series filtering criteria. Relaxed criteria required at least four years of counts, one of which had to be non-zero (n = 5,328 out of 6,501 trends remained). Moderate criteria required at least eight years of counts, of which four had to be non-zero (n = 2,266 trends remained). Strict criteria required at least 15 years of counts, of which 10 had to be non-zero, and that temporal autocorrelation be < 1 (n = 308 trends remained).
Extended Data Fig. 4 Explanatory variables overlaid on (sorted) time trends in arthropod abundance among LTERs.
(a) Start year of LTER site sampling. (b) Human Footprint Index associated with LTER site. The average HFI value for locations within the US is 7; LTER sites ranged from 1 to 38. (c) Mean annual temperature at LTER sites. (d) Mean cumulative annual precipitation at LTER sites.
Extended Data Fig. 5 Importance of explanatory variables in predicting time trends of arthropod abundance.
Contribution of each variable to the accuracy of the Random Forests classifier, defined as the percent increase in Mean Square Error (decrease in accuracy) when the variable was excluded from decision trees.
Extended Data Fig. 6 Time trends in arthropod abundance, average among studies with similar start years.
Abundance trends are averaged among LTERs where sampling start years were earlier than 1990, spanned 1990–2000, spanned 2000–2010, or were after 2010. Results were the same when trends were grouped according to final sampling years (except that no final sampling years predated 1990).
Dots represent the change over time of a diversity metric at an LTER site. Species evenness was calculated as Pielou’s Evenness Index, and dominance represents the proportional frequency of the most abundant taxon. Light gray lines divide each plot into quadrants to help visualize sites where the sign of change in diversity metrics was similar (top right, bottom left) or opposite (top left, bottom right). Black dashes denote the line of best fit. Slopes are significant at the α = 5% level, R2 = 0.36 for evenness vs. richness, and R2 = 0.68 for evenness vs. dominance.
Left panel depicts abundance trends separated by ecoregion level I. Right panel depicts abundance trends separated by ecoregion level II. Boxplots depict quantiles among LTER sites. Boxplots depict trends among insects as medians (thick line), 25th and 75th percentiles (box edges), 95th percentiles (whiskers), and outliers (circles).
Human Footprint Index values in the USA (left panel) and among LTER sites (right panel).
Dots represent the change over time of a diversity metric at an LTER site. The grey dashed line denotes the 1:1 line.
About this article
Cite this article
Crossley, M.S., Meier, A.R., Baldwin, E.M. et al. No net insect abundance and diversity declines across US Long Term Ecological Research sites. Nat Ecol Evol (2020). https://doi.org/10.1038/s41559-020-1269-4