a million species
Insects and other arthropods shape life on Earth in ways that few groups do. They fill ecosystems, fertilize soils, pollinate crops, and form the backbone of many food webs. Scientists from the Weizmann Institute of Sciences in Israel highlight how these tiny beings underpin biodiversity and global ecological health. Their work suggests that the absence of arthropods would be felt across ecosystems and could alter climate-related processes in surprising ways.
Arthropods, including arachnids and crustaceans, are described as ecosystem engineers. They support agricultural landscapes, renew degraded lands, and provide sustenance for many predators. Yet recent studies reveal a notable decline in arthropod numbers, which worries researchers about the ripple effects on human society and natural systems.
Arthropods have earned the label of “the little things that rule the world” because of their central roles in many ecological processes. Understanding their abundance helps reveal how humanity’s actions and climate trends shape the planet. Yuval Rosenberg and Yinon M. Bar-On led a broad global assessment that stresses how important these creatures are to our environment and future conditions.
Termites, the most numerous subterranean social insects, are often cited as a key example of arthropod dominance below the surface.
Measuring arthropod populations provides a baseline for predicting future shifts in these communities and how those shifts might influence global processes. This is a critical step in mapping how ecological change tracks with climate and human activity.
a million species
Because data on world population abundance for these invertebrates has been sparse, the Israeli team compiled thousands of assessments from nearly 500 sites across the globe. From tropical rainforests to deserts, farmlands to subsoils, they estimated the absolute biomass and abundance of terrestrial arthropods across different groups and habitats.
The researchers estimate the total biomass of terrestrial arthropods at about one billion tons—roughly the combined weight of all humans plus livestock. The findings show that most of this biomass lives underground, with groups such as bowtails and mites playing vital roles in the hidden ecology beneath our feet.
Subterranean arthropods drive soil fertility and influence the global carbon cycle. They feed on other organisms, helping maintain ecological balance. The number of individual underground arthropods is huge, with mites and springtails making up the majority of this underground world—roughly ten trillion individuals. Social insects like termites and ants constitute a significant share of subterranean biomass, while surface arthropods dominate in tropical forests. Common surface arthropods include butterflies, ants, beetles, grasshoppers, and spiders.
Human and climatic conditions
Researchers note that species with large populations or heavy biomass tend to have greater ecological impact. Measuring global arthropod mass helps build a clearer picture of how ecological processes operate and how human activity and climate influence them. The study challenges the notion that arthropod populations are endless. Despite wide distribution, many species are affected by human actions and climate shifts, which makes ecological systems more vulnerable.
For example, farmland generally shows lower arthropod abundance than forests within the same climate zone. The health of Earth’s ecological systems depends largely on the state of arthropod populations. They regulate vegetation, support thousands of bird, reptile, and amphibian species, and contribute to the breakdown and recycling of dead matter and waste. This has meaningful implications for health, agriculture, and the economy alike.
Even seemingly small services, like soil conditioning and pest suppression, matter greatly. A broad, quantitative perspective helps assess how declines in arthropod populations might alter ecological systems and, in turn, affect human health and livelihoods. The researchers emphasize careful monitoring to track these changes and understand their consequences for biodiversity and resilience.
Reference: Science Advances, doi: 10.1126/sciadv.abq4049. The study underscores the need for ongoing observation of arthropod communities and their responses to climate and land-use changes.
The environmental assessment emphasizes that the state of arthropod populations bears on ecological balance and ecological services that humans rely on, from soil fertility to food webs. Ongoing research and monitoring are essential to anticipate and mitigate impacts on health, agriculture, and quality of life, as natural systems respond to a changing climate.