20% of Plants Have Mysterious Deep Roots — And They Might Store Carbon
Scientists thought for a long time that plant roots followed a simple rule: the deeper you go, the fewer roots there are. But a new study published in Nature Communications has turned this long-held belief on its head. It shows that 20% of plants around the world grow a second set of roots more than 3 feet (1 metre) underground, which researchers call "bimodality." This finding not only changes what we know about plants, but it also suggests that they may be fighting climate change by storing carbon much deeper than we thought.
The study, led by New York University ecologist Mingzhen Lu, used a dataset from the National Ecological Observatory Network (NEON) that had never been used before. It took samples of soil from 44 places around the world, from the frozen Alaskan tundra to the hot rainforests of Puerto Rico. What they found goes against everything we thought we knew about how plants survive and how they fit into the carbon cycle on Earth.
The Discovery: Roots That Defy Convention
A recent field survey found that roughly one in every five plants-20 per-cent-exhibits a surprisingly tactical dual-root setup. An unexpected second cluster of density almost disappears into the subsoil; in most cases it nestles three to six feet-one to two meters-en-tirely underfoot.
- Measurements show these deep strands steer straight toward mineral sheets loaded with nitrogen, phosphorus, and other forgotten reserves. Once surface moisture vanishes or competition spikes, the backup roots spring into action.
- Decades of computerized ecolog-ical models lazily assumed that root vigor dropped off sharply once the spade hit any real depth. Ground-huggers like Lu phrase it bluntly: Above our heads satellites grant eagle vision; below our heels only mole vision has prevailed.
Because scientists overlooked that hidden renewal zone, they likely sold plants short when estimating their carbon-storage capacity. In those chill, lowe-r strata where microbes chew slowly, woody biomass can bank carbon for a generation or more.
The Blind Spot: Why Science Missed This
For years researchers missed the story buried in the soil simply because they stopped digging. Standard field practice seldom reaches past 30 centimetres-just about the working range of a garden spade and a tireless graduate student. NEON crews, methodically boring to 2 metres, unwittingly filmed the plot twist unfold.
The notion that roots stretch farther than textbooks promise is hardly revolutionary; ambitious scientists of the 1970s caught glimpses but labeled those finds statistical flukes. Modern gear changed the odds. Deep-core drills and 3D scans now let teams chart subterranean networks with the same precision they bring to aerial surveys.
Climate Resilience: How Deep Roots Help Plants Survive
Bimodal roots might be why some ecosystems can handle extreme weather better than models say they should. When the top layer of soil dries out, deep roots act like emergency lifelines, bringing up water and nutrients from below.
- It might be that forests with deep-rooted species are more resistant to drought than we thought.
- Crops with bimodal roots might do well in dry areas, which would mean less need for irrigation.
Tilling and cutting down trees could be worse than we thought because they break up hidden root networks that keep the soil stable and store carbon.
The Road Ahead: From Discovery to Solutions
The study opens up new possibilities for climate policy, carbon farming, and reforestation. If deep roots really do help store carbon for a long time, agroforestry and cover cropping could be improved to encourage deeper rooting.
Next Steps for Science:
- Mapping the prevalence of bimodality by expanding deep-soil sampling around the world.
- Growing crops with deep roots to store carbon and survive droughts.
- Changing carbon credit systems so that they reward storing carbon in the ground, not just in organic matter on the surface.
Lu says, "The good news is that plants may already be helping to slow down climate change more than we thought." "We just need to look deeper to see how much they can do."
