The environment fighting back on its own
On the windswept clifftops of the Isle of Wight, a young scientist's curiosity about dying moss patches has led to the discovery of something rare in the long struggle against invasive species: nature offering its own remedy. A previously unknown fungus, now called moss die-back, is selectively dismantling the heath-star moss that has smothered Britain's native landscapes since the 1940s, opening ground for the return of ancient ecosystems. In a country where one in six species faces extinction and human intervention has long been the costly default, this quiet fungal uprising represents an unexpected, and perhaps hopeful, turn in the story of ecological loss.
- Heath-star moss, an aggressive southern-hemisphere invader, has spent eight decades overwhelming Britain's native mosses, threatening the temperate rainforests and carbon-storing peatlands that depend on them.
- A single scientist, largely working alone, is racing to document a fungus that no one had formally identified before — a discovery that could reshape how Britain approaches its biodiversity crisis.
- Unlike the expensive, ongoing campaigns against grey squirrels or Japanese knotweed, this fungus appears to do its work freely and selectively, sparing native species while dismantling the invader.
- DNA analysis links the fungus to the devastating ash die-back pathogen, yet its behaviour is strikingly different — targeted rather than indiscriminate, raising urgent questions about its origins and limits.
- In the gaps left by dying invasive moss, baby heather and native plants are already returning, offering a visible, if fragile, sign that the landscape is beginning to breathe again.
- Scientists are now combing through Victorian-era herbarium specimens to trace when this fungus first appeared, hoping to understand how to support its spread before the window of opportunity narrows.
Four years ago, George Greiff was walking a clifftop on the Isle of Wight when he noticed patches of dead moss scattered across the landscape. Collecting samples out of curiosity, he began a slow collaboration with colleagues in the UK and France that would eventually yield something extraordinary: a fungus no scientist had ever formally named, one that attacks heath-star moss — the aggressive invader that has been overwhelming Britain's native plant life for decades.
Heath-star moss arrived in Britain in the 1940s, likely carried from the southern hemisphere, and by 1990 it had spread across hillsides, sand dunes, and garden fences alike. Pretty to look at but relentless, it displaced roughly a thousand native moss species that underpin some of Britain's rarest ecosystems — temperate rainforests, carbon-storing peatlands, heathlands where native mosses have now all but vanished. Britain has faced around two thousand non-native invaders over the centuries, and controlling them has typically demanded expensive, labour-intensive human effort. The newly named moss die-back fungus offers something different: a natural mechanism that works without intervention.
Under a microscope at Amgueddfa Cymru museum in Cardiff, where Greiff is based, the fungus reveals itself clinging to moss stems and ballooning around them, even penetrating individual cells. DNA sequencing shows it is a close relative of ash die-back, which has killed up to eighty million ash trees across Britain — yet its behaviour appears far more selective, targeting the invasive moss while leaving other species largely untouched. Greiff believes it may be a native organism that adapted over time to attack the invader, a rare instance of the British environment mounting its own defence.
In Bannau Brycheiniog national park, the evidence is quietly visible: brown rings of dead moss, and within them, baby heather and native plants reclaiming the ground. At the museum, head of plant science Dr Nathan Smith is examining historical specimens dating to the 1880s, hoping to trace exactly when the fungus emerged and how it has spread — knowledge that could help scientists support its natural advance.
Against the backdrop of Britain being among the most nature-depleted countries on Earth, with one in six species at risk of extinction, the discovery carries real weight. Yet Greiff remains the only scientist actively searching for the fungus, mapping its locations with what he wryly notes is also a record of his holidays. He is calling for others to join the effort — because the work of understanding, and perhaps nurturing, this unexpected ally has only just begun.
Four years ago, a young scientist named George Greiff was walking along a clifftop on the Isle of Wight when he noticed something unusual: patches of dead moss scattered across the landscape. He collected samples, curious about what was killing them, but the answer didn't come easily. Over time, as he kept spotting more of these mysterious die-offs, Greiff began working with colleagues in the UK and France to solve the puzzle. What they eventually discovered was a fungus no scientist had ever formally identified before—one that attacks the heath-star moss, an aggressive invader that has been choking out Britain's native plant life for decades.
The heath-star moss arrived in Britain sometime in the 1940s, likely hitching a ride from the southern hemisphere. By 1990, it had spread everywhere. Walk through a hillside, across sand dunes, or even look at a garden fence, and you'll find it. Greiff describes it as pretty to look at, but relentless in its conquest. The moss reproduces quickly, sends spores far and wide, and has proven devastatingly successful at displacing the thousand or so native moss species that once thrived here. Those native mosses form the foundation of some of Britain's most irreplaceable ecosystems—the rare temperate rainforests of damp coastal woodlands, the carbon-storing peatlands. As the invasive moss took over, these habitats shrank. In heathlands near Abergavenny in south Wales, native mosses have either vanished locally or declined so sharply they barely register anymore.
Britain has been invaded by roughly two thousand non-native plants and animals over the centuries, some arriving by accident, others deliberately introduced. The grey squirrel from North America nearly extinguished the native red squirrel. Japanese knotweed damages homes. Rhododendron poisons the soil. Usually, controlling these invaders requires expensive, labor-intensive human intervention—like the ongoing effort to feed contraceptives to grey squirrels. But the fungus Greiff discovered offers something rare: a natural biological control that works without human effort or cost.
The fungus, now named moss die-back, clings to the moss stem and balloons around it like spun sugar on a stick, even penetrating some of the moss cells. Under a microscope in the lab at Amgueddfa Cymru museum in Cardiff, where Greiff works, the mechanism of destruction becomes visible. DNA sequencing revealed that the fungus is a close relative of the ash die-back fungus, which has killed up to eighty million ash trees across Britain. Yet here's the crucial difference: Greiff's analysis suggests the moss die-back fungus targets only the invasive heath-star moss, and perhaps one other moss species to a limited extent. It appears to leave other plants and animals untouched.
Greiff theorizes that this fungus may have originated as a native species that adapted over time to attack the invasive moss—a rare example of the British environment fighting back on its own. When you walk through the Bannau Brycheiniog national park with him, he points out the brown rings of dead moss, barely dramatic to the naked eye. But zoom in with a macro lens and you see the white fungal blobs at work. More importantly, you see what comes next: baby heather plants and other native species now able to grow in the gaps left behind.
At the museum, Dr. Nathan Smith, the head of plant and earth science, opens cabinet drawers holding the oldest moss collection in the UK—dried specimens in paper envelopes dating back to the 1880s. By examining these historical samples for evidence of the fungus, scientists hope to pinpoint exactly when and how it appeared. This detective work matters because it could help them understand whether the fungus is spreading naturally, and how to support that spread. Smith sees the potential clearly: the fungus offers a chance to restore the unique moss landscapes that shelter insects, fungi, molluscs, and plants found nowhere else.
Britain's nature is among the most depleted in the world, with one in six species at risk of extinction. Against that backdrop, discovering a natural control on habitat destruction feels like a small miracle. Yet Greiff remains the only scientist actively searching for this fungus. He jokes that his map of where it's been found is also a map of his holiday destinations. He's calling for others to join the search, to help document the fungus's spread and unlock its full potential. The work is just beginning, but for the first time in decades, native British habitats have an unexpected ally in their fight to survive.
Citas Notables
To have a natural biological control agent doing it for us is really valuable— Dr. George Greiff
This fungus gives an opportunity to save these unique moss landscapes that are homes for insects, fungi, molluscs, other plants— Dr. Nathan Smith, Head of Plant and Earth Science
La Conversación del Hearth Otra perspectiva de la historia
When you first found that dead moss on the Isle of Wight, did you immediately suspect a fungus?
Not at all. I had no idea what I was looking at. I threw the first sample in the bin. It took years of seeing more cases, working with colleagues, and doing DNA sequencing before we understood what we were dealing with.
The heath-star moss sounds almost innocent—just another plant. Why is it such a problem?
It's the speed and aggression. It reproduces quickly, sends spores everywhere, and it's so successful at crowding out everything else that native mosses have gone locally extinct in some places. I've seen it growing in tarmac. It's relentless.
And this fungus only kills that one moss? That seems almost too convenient.
It does seem fortunate, doesn't it? Our analysis suggests it targets the invasive moss and perhaps one other species to a limited extent. But we're still doing the work to confirm that. The fungus appears to be a native species that adapted to attack the invader—the environment fighting back.
If this fungus is so effective, why isn't it already everywhere, controlling the problem?
It is spreading, but slowly. We're still mapping where it occurs. That's partly why I'm calling for other scientists to help search. Right now, I'm essentially doing this alone, and there's so much more we could learn about how to support its natural spread.
What would happen if you tried to deliberately introduce this fungus to infested areas?
That's the question we need to answer carefully. We need to understand its ecology better first—how it spreads, what conditions it needs, whether there are any unintended consequences. We can't just release it without knowing more.
Those old moss samples in the museum drawers—what are you hoping to find in them?
We want to know when this fungus first appeared. Did it emerge recently, or has it been here longer than we realized? Understanding its history might tell us whether it's a natural adaptation or something else entirely. That knowledge could help us predict how it will spread.