It started with a grass. A dense, fast-spreading, invasive grass called *Spartina anglica* — rice grass — that had colonised the coastal wetlands of north-west Tasmania, smothering the saltmarsh and turning thriving estuarine habitat into a biological desert. When scientists removed it, what happened next was extraordinary.
New research from the University of Tasmania, published in March 2026, reveals that removing Spartina from two coastal wetland sites — **Duck Bay** and **Morgans Bay** — triggered a cascade of ecological recovery that far exceeded expectations. Within just three years of treatment, the number of fish species recorded in restored areas more than doubled, from five to eleven. Total fish numbers increased by roughly **twentyfold**.
At Morgans Bay, where fish had been almost entirely absent before the invasive grass was cleared, researchers recorded **255 fish per 100 square metres** by 2023. That density matches what you'd find in undisturbed, healthy saltmarsh — a habitat that the bay hadn't supported in years.
**What Spartina Does to a Wetland**
Spartina anglica is a hybrid grass, originally from the UK, that was introduced to various parts of the world in the 19th and 20th centuries for coastal stabilisation. It's extraordinarily effective at one thing: turning mudflat into dense grassland. It does this by trapping sediment, building up land, and outcompeting every other plant species around it.
That sounds neutral, or even useful. But coastal wetlands — saltmarshes, estuaries, tidal mudflats — are among the most productive ecosystems on Earth, precisely because of their complex structure. Fish, crustaceans, and invertebrates depend on the open mudflat areas to feed. Birds depend on those animals. The whole food web is built on the bare, accessible, nutrient-rich mud that Spartina relentlessly paves over.
Once the grass moves in, the ecosystem effectively goes quiet. The mud disappears under a dense green blanket. The fish can't access it. The birds leave. The wetland becomes a monoculture.
**The Removal Campaign**
The Circular Head Landcare Group, working with government support through Australia's National Landcare Program (funded from 2019), undertook the removal using multiple methods including herbicide application by drone — a technique that allowed precise treatment of the dense grass mats without disturbing the surrounding habitat.
The treatment wasn't quick or cheap. Spartina is persistent. The rhizomes (underground root systems) survive if not fully killed, and re-treatment is often necessary across multiple seasons. But the group persisted, and the results have now been measured and published.
**Nature Moves Fast When Given the Chance**
Perhaps the most striking finding of the study is the *speed* of recovery. Three years. That's all it took for fish species diversity to double and total numbers to increase twentyfold. For an ecosystem that had been degraded for decades, that's a remarkable turnaround — and it carries an important message for conservationists worldwide.
Coastal wetlands — including saltmarshes, mangroves, and seagrass meadows — are often discussed as 'blue carbon' ecosystems because of their extraordinary capacity to sequester carbon dioxide from the atmosphere. They also serve as nurseries for commercially important fish species, as buffers against storm surges, and as filtration systems that clean coastal water before it reaches the sea.
The Tasmanian study joins a growing body of evidence that these ecosystems, when given the chance to recover, can do so with surprising speed. The bottleneck is not time — it's access. Remove the threat, and the life returns.
**A Proof of Concept for Global Restoration**
Spartina anglica has spread to coastal wetlands across Australia, New Zealand, China, the United States, and parts of Europe. Each infestation represents a version of the same story: a productive, biodiverse ecosystem slowly silenced by a single, relentless invader. The Tasmanian research offers a template for what restoration can achieve — and a compelling argument for scaling up removal programs worldwide.
'This research demonstrates that coastal wetlands can recover rapidly if invasive species are removed,' the study concludes. 'The wetlands function as both nursery and feeding ground for fish — and that function returns quickly once the habitat is restored.'
For the fish that have flooded back into Morgans Bay, the grass is gone. The mud is back. And the water is alive again. 🐟
*Sources: University of Tasmania (March 2026) · Mirage News · Pulse Tasmania · Circular Head Landcare Group · Australian Government National Landcare Program · NRM South Tasmania*
