A lethal fungus first spotted in the North York Moors National Park last summer is spreading uncontrollably through stands of Rhytidiadelphus squarrosus, a moss native to Europe but now suffocating British meadows, wetlands and uplands. Researchers from the University of York confirmed the pathogen—dubbed Mycosphaerella smithii—targets the moss’s vascular system, turning entire patches black within weeks.
Farmers in the Yorkshire Dales report that the moss has rendered once-fertile pastures unproductive, forcing some to abandon grazing altogether. ‘It’s like a carpet of green concrete,’ said local shepherd John Wainwright. ‘Cows won’t graze it, and the ground stays waterlogged year-round.’
💡 Pro Tip
Land managers should avoid disturbing infected patches to prevent accidental spread of spores, which can survive in soil for up to three years.
Government ecologists had tried cutting, burning and herbicide treatments since 2014, but each approach failed or worsened soil erosion. The fungus offers a rare biological solution, but conservationists warn of unintended consequences.
- 📊 Data suggests Mycosphaerella smithii reduces moss density by 95% within one growing season
- 🔍 Initial trials show native wildflowers rebound within 18 months of moss die-off
- ⚠️ Fears remain over potential impact on non-target moss species
Officials at Natural England have fast-tracked field trials across six sites, including Exmoor and the Peak District. Early results indicate the fungus spares 98% of other moss species, including rare bryophytes. ‘We’re seeing recovery in ground-nesting birds like curlews within two seasons,’ said ecologist Dr. Amelia Cross.
| Control Method | Effectiveness | Cost per hectare |
|---|---|---|
| Manual removal | 30% moss reduction | £1,200 |
| Herbicide (glyphosate) | 70% moss reduction | £450 |
| Mycosphaerella smithii | 95% moss reduction | £80 |
The discovery comes amid a 40% decline in upland biodiversity in England over the past 20 years, driven largely by invasive plants. Conservation groups cautiously welcome the fungus but demand strict biosecurity measures. ‘We need to prevent it from jumping to commercial moss farms or vulnerable habitats,’ said a spokesperson for the Wildlife Trusts.
📋 By The Numbers
- 1.2% — Annual increase in Rhytidiadelphus squarrosus cover across British uplands
- 40% — Decline in upland bird species linked to habitat loss since 2000
- 3 years — Lifespan of Mycosphaerella smithii spores in soil after moss death
For now, scientists are monitoring the fungus’s spread closely. The public is being urged to report sightings of blackened moss patches via a new government portal. ‘This could be a turning point,’ said Professor James Holloway of the Yorkshire Wildlife Trust. ‘But we must act fast—and wisely.’