It’s time for ecologists and conservation biologists to dig deeper into dirt—in order to better understand the threats facing soil creatures that are key to healthy ecosystems and our food supply, and that might offer a rich source of potential antibiotics.
“Despite marked progress over the last few decades, currently soil ecology still lags far behind aboveground ecology, and our knowledge of the world belowground is comparatively limited,” soil ecologist Stavros Veresoglou of the Free University of Berlin and colleagues conclude in one of the papers, appearing in Nature Communications. In particular, they note, studies of the extinction risks faced by soil organisms “are alarmingly sparse.”
“We need to be studying extinctions in soil and the time to start is now,” says Matthias Rillig, a co-author of the paper and a soil microbiologist at the Free University of Berlin. “Given what we’re doing to the planet in terms of land use and global climate change, there is a concern among soil scientists that we may be missing something going on.”
Already, the authors note, some studies have documented local extinctions of earthworms and wood-decomposing fungi because of species invasions or changing environmental conditions. But researchers have tended to downplay the risks of soil extinctions, in part because of the perception that soil microbes and other subterranean organisms are widely distributed around the globe. In many places, however, scientists have little idea of what is living in the soil or the novel roles played by individual organisms.
Now, soil scientists say a suite of new tools, including advanced DNA sequencing methods that can determine how many types of microbes are living in a sample of dirt or water, could help researchers fill in the gaps. Some researchers, for instance, are using such tools to uncover the so-called rare biosphere—the large number of diverse microbes that persist in low abundance in a soil sample.
“If we can get a handle on rare biosphere, we might be able to say if there is or is there not any extinction,” says Jonathan Eisen, a microbiologist at University of California, Davis. But one challenge is that sequencing tools can’t determine whether the detected DNA came from a living or dead organism. And because microbes can multiply rapidly, their populations can change with the season or the weather. Just because something is rare now doesn’t mean it is rare at some other time, Eisen notes.
Inspiring scientists to launch studies to better understand such dynamics is just one of the goals of World Soil Day, which is helping cap a year-long research and outreach initiative known as the International Year of Soils. Eisen, for one, laments not being able to jump into a soil submarine to explore underground, the way marine biologists examine the deep sea. But he and other researchers say that, until someone invents such a craft, there are plenty of other ways we can better understand what’s going on beneath our feet, if we just take the time to look.