Image Source: Adobe Stock
The world is teeming with ants. In fact, ants are the most abundant creatures on earth, totaling more than 20 quadrillion individual bugs across more than 15,700 different known species. If you weighed every ant in the world together and then did the same for every person in India and the USA combined, the weights measured by each of these scales would be about the same.
Not only are they numerous, but these little critters are also industrious, playing a hefty role in decomposing and redistributing nutrients in biomes across nearly every country on the globe. Given all that ants contribute to the world, it seems like we should keep better track of them.
Luckily, there are scientists are on the job.
In a recent study conducted at the University of Hong Kong, School of Biological Sciences, researchers compiled data from 465 scientific papers to better quantify the number of ants on the planet. To learn more about why they did this, we interviewed the study’s primary contributors: Dr. Patrick Schultheiss (PS) and Dr. Sabine S. Nooten (SN). After reading their responses, you might welcome these little critters a bit more the next time they join you on a picnic.
CTS: Clearly based on your study, there are a lot of ants on the globe. Why is quantifying them important?
PS: We have known for a long time that ants are extremely important members of almost all ecosystems. Countless studies have shown that they are crucial for nutrient cycling, plant seed dispersal, soil churning and the decomposition of biological matter. These tasks are really important for keeping ecosystems going. A single ant doesn’t do much of this of course, because it is so small. But they are usually extremely abundant and as a whole, their impacts can be truly staggering. For example, one study has estimated that ants can move up to 13 tons of soil per hectare every year. So to understand something about their importance in different ecosystems, we need to know about their abundance.
SN: No one had ever looked at the global pattern of ant abundances, so it was not clear if some parts of the world are particularly rich – or particularly poor – in ant abundance. We searched through many thousands of published studies and found almost 500 that had collected ants with standard methods and reported two different measures: the collecting effort, and the number of ants they collected. From this, we could create a global map of typical ant density and could compare different regions of the world with each other. We found the highest numbers of ants in tropical regions, especially in forests and dryland such as savannas.
Ultimately, we could also estimate the total number of ants on Earth from our dataset, and we got this really huge number of 20 quadrillion – which is a 20 with 15 zeros. We can’t really imagine such a number, but if we translate this into an estimate of ant biomass, it actually exceeds the biomass of all wild birds and wild mammals combined. And suddenly we begin to appreciate just how important ants are.
Estimates of (A) global ant abundance and (B) biomass.
Image Credit: 10.1073/pnas.2201550119
CTS: If ants were to disappear entirely from an ecosystem, what would be the first noticeable change?
PS: Let’s hope this never actually happens, or we humans are in deep trouble… There’s a reason why E.O. Wilson called them “the little things that run the world”. It’s very difficult to predict what exactly would happen and where, because ants are highly diverse and do many kinds of things. There are in fact a lot of different species – we currently know of almost 16,000 species and subspecies and are still discovering more every year. Ants come in very different shapes and sizes, and they all have their own specialization.
SN: One of the first changes we could expect is the accumulation of dead biomatter. As we know from our picnics, it doesn’t take long for ants to find the piece of cheese we dropped… Our own research has also shown that ants play an important role in the decomposition of animal carcasses. A further immediate change would probably be a strong increase or decrease in the abundance of many other small critters. Ants hunt and eat a lot of different invertebrates and are also eaten by many other animals. With ants gone, there would be huge shifts in the populations of other animals as well. A third massive change, which might take a few weeks to be noticed, will affect the plants of course. The interactions between ants and plants are very close and diverse, for example by helping to distribute seeds or by harvesting leaves (as leafcutter ants do).
CTS: You’ve done extensive research on ants in the past; what motivated you to study ants?
PS: That’s true, I’ve been working on ants in earnest since 2008, when I started my PhD studies. And to be honest, I didn’t pay ants any particular attention before that. But then I started observing ant behaviour, and learning about all the different things they can do… and I was hooked. The more I know about them, the more fascinated I am.
For example, during my PhD I studied a single species of desert ant in Australia – the honey pot ant Melophorus bagoti. They leave the nest during the day in the heat of summer, which can be extreme in the desert. I’ve measured ground temperatures of up to 75º Celsius. As the ground is too hot to lay pheromone trails, each individual ant has to be adept at navigating visually, and they are absolute experts.
Honey pot ants
Image Source: Shutterstock.com
It’s stunning to follow an ant around the grass clumps of the Outback for an hour or so, and see her heading home in a straight line when she finally finds a scrap of food! Some desert ants can even do this in the bleakest environments, such as a dry salt lake where they can only use the position of the sun for orientation. And they do all this with the tiniest of brains.
SN: I am intrigued by patterns in nature – as a community ecologist, I look at patterns of species and traits, to find out why organisms live where they do. I’ve been studying ants since 2008, and I am fascinated by their amazing diversity, in color, sculpturing and size. When you’re getting a close-up view under the microscope you see all sorts of crazy spines, hairs, and metallic shimmering surfaces. My favorite ant is the green-headed ant Rhytidoponera metallica. Its entire body is green/purple iridescent – very beautiful.
CTS: In your professional opinion, what other insects deserve more attention than they’ve received?
PS: I’m sure they all “deserve” more attention. It is often quite shocking how little we really know about the natural world, even when it’s clearly of huge benefit to us humans.
The study was published in the journal PNAS.
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