The abundance, biomass, and distribution of ants on Earth

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Significance

The astounding ubiquity of ants has prompted many naturalists to contemplate their exact number on Earth, but systematic and empirically derived estimates are lacking. Integrating data from all continents and major biomes, we conservatively estimate 20 × 10 ¹⁵ (20 quadrillion) ants on Earth, with a total biomass of 12 megatons of dry carbon. This exceeds the combined biomass of wild birds and mammals and equals 20% of human biomass. Ant abundance is distributed unevenly on Earth, peaking in the tropics and varying sixfold among habitats. Our global map of ant abundance expands our understanding of the geography of ant diversity and provides a baseline for predicting ants’ responses to worrying environmental changes that currently impact insect biomass.

Abstract

Knowledge on the distribution and abundance of organisms is fundamental to understanding their roles within ecosystems and their ecological importance for other taxa. Such knowledge is currently lacking for insects, which have long been regarded as the “little things that run the world”. Even for ubiquitous insects, such as ants, which are of tremendous ecological significance, there is currently neither a reliable estimate of their total number on Earth nor of their abundance in particular biomes or habitats. We compile data on ground-dwelling and arboreal ants to obtain an empirical estimate of global ant abundance. Our analysis is based on 489 studies, spanning all continents, major biomes, and habitats. We conservatively estimate total abundance of ground-dwelling ants at over 3 × 10 ¹⁵ and estimate the number of all ants on Earth to be almost 20 × 10 ¹⁵ individuals. The latter corresponds to a biomass of ∼12 megatons of dry carbon. This exceeds the combined biomass of wild birds and mammals and is equivalent to ∼20% of human biomass. Abundances of ground-dwelling ants are strongly concentrated in tropical and subtropical regions but vary substantially across habitats. The density of leaf-litter ants is highest in forests, while the numbers of actively ground-foraging ants are highest in arid regions. This study highlights the central role ants play in terrestrial ecosystems but also major ecological and geographic gaps in our current knowledge. Our results provide a crucial baseline for exploring environmental drivers of ant-abundance patterns and for tracking the responses of insects to environmental change.

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The biomass distribution on Earth

Yinon M. Bar-On, Rob Phillips, Ron Milo (2018)

Significance The composition of the biosphere is a fundamental question in biology, yet a global quantitative account of the biomass of each taxon is still lacking. We assemble a census of the biomass of all kingdoms of life. This analysis provides a holistic view of the composition of the biosphere and allows us to observe broad patterns over taxonomic categories, geographic locations, and trophic modes.

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Defaunation in the Anthropocene.

Rodolfo Dirzo, Hillary S Young, Mauro Galetti … (2014)

We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this "Anthropocene defaunation"; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet's sixth mass extinction and also a major driver of global ecological change. Copyright © 2014, American Association for the Advancement of Science.

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More than 75 percent decline over 27 years in total flying insect biomass in protected areas

Caspar A Hallmann, Martin Sorg, Eelke Jongejans … (2017)

Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

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Author and article information

Journal

Journal ID (nlm-ta): Proc Natl Acad Sci U S A

Journal ID (iso-abbrev): Proc Natl Acad Sci U S A

Journal ID (hwp): pnas

Journal ID (publisher-id): PNAS

Title: Proceedings of the National Academy of Sciences of the United States of America

Publisher: National Academy of Sciences

ISSN (Print): 0027-8424

ISSN (Electronic): 1091-6490

Publication date (Electronic): 19 September 2022

Publication date (Print): 4 October 2022

Publication date PMC-release: 19 March 2023

Volume: 119

Issue: 40

Electronic Location Identifier: e2201550119

Affiliations

[1] ^aSchool of Biological Sciences, The University of Hong Kong , Hong Kong SAR, China;

[2] ^bBehavioral Physiology and Sociobiology, Universität Würzburg , 97074 Würzburg, Germany;

[3] ^cAnimal Ecology and Tropical Biology, Universität Würzburg , 97074 Würzburg, Germany;

[4] ^dSchool of Biological Sciences, The University of Western Australia , Crawley, WA 6009, Australia;

[5] ^eCentre for Environment and Life Sciences, Commonwealth Scientific and Industrial Research Organisation, Health & Biosecurity , Floreat, WA 6014, Australia;

[6] ^fResearch Institute for the Environment and Livelihoods, Charles Darwin University , Darwin, NT 0810, Australia

Author notes

²To whom correspondence may be addressed. Email: ppschultheiss@ 123456gmail.com .

Edited by Vojtech Novotny, Biologicke centrum Akademie ved Ceske republiky, Ceske Budejovice, Czech Republic; received January 28, 2022; accepted August 9, 2022 by Editorial Board Member Pablo A. Marquet

Author contributions: P.S., S.S.N., R.W., M.K.L.W., F.B., and B.G. designed research; P.S., S.S.N., R.W., M.K.L.W., F.B., and B.G. performed research; P.S., S.S.N., and R.W. analyzed data; and P.S., S.S.N., R.W., M.K.L.W., F.B., and B.G. wrote the paper.

¹P.S. and S.S.N. contributed equally to this work.