A Quarter of Britain's Biggest Reed Bed Burned. Being Wet Didn't Save It

Quick summary

• Fire feeds on dead, dry vegetation, not on how wet the ground is. A waterlogged reed bed still lost a quarter of its area in a day.

• The Tay fire spread because cutting had stopped and the fire breaks were gone, leaving years of accumulated fuel.

• Rewetting manages water, not fuel. On its own it is not a wildfire prevention tool.

• Keeping these sites intact means active management: cutting, controlled burning where suitable, and maintained breaks.

In April 2020, fire destroyed around 125 hectares of the UK's largest reed beds on the River Tay: roughly a quarter of the whole system.

These are among the wettest habitats in Britain, waterlogged for most of the year. They still carried a fast-moving wildfire that took nine fire appliances and a helicopter to control.

If you manage vegetation on any scale, that is the fact worth noting. Wildfires burn the dead, dry material sitting on top of the ground, regardless of how wet that ground is. The Tay reed beds had plenty of that fuel.

What burned

The fire took hold near Errol, Perthshire, on 27 April 2020, during a dry spell after an unusually hot April. According to the Tay Ringing Group, which has monitored the site's birds for decades, the damage was severe:

• Around 125 hectares burned — about a quarter of a reed bed system that runs for nine miles along the north bank of the Tay and forms the 410-hectare Inner Tay Estuary Local Nature Reserve, protected under four national and international designations.

• The site holds the UK's largest population of bearded tits, Scotland's most important nesting area for water rails, and most of the small Scottish population of breeding marsh harriers.

• Two marsh harrier nests and most of the prime bearded tit habitat were lost, with broken shells from around 30 burnt-out nests found in the ash.

Investigators found no lightning, and Steve Moyes of the Tay Ringing Group judged the fire to have been set deliberately. Ignition is one thing. How far and how hot a fire runs once lit is another, and that is where management decides the outcome.

Why wet ground didn't stop it

A reed bed sits in water. Its living stems are green and hard to burn. But every season leaves behind a layer of dead reed, and where that litter is never removed it builds into a deep, continuous bed of fuel that dries at the surface and carries fire readily.

Two management failures made the Tay fire worse, and both are familiar to anyone who works this kind of ground:

• Fuel had been left to accumulate. The reeds were once cut on rotation each winter for thatching. That cutting stopped around 15 years earlier when it became uneconomic, and the old growth was left standing season after season.

• The natural fire breaks went with it. Rotational cutting had left a patchwork of cut and uncut ground that slowed any fire's advance. Once that stopped, there was little to break the fire's run. Moyes, a former firefighter, pointed to the absence of fire breaks and the lack of reed management as reasons it spread so far.

What this means for the rewetting debate

Wildfire in protected sites is a very real risk. SNH reported that half of all land burnt by wildfire in Scotland in 2019 — 5,860 of 11,710 hectares — lay inside protected wildlife sites. The places we most want to protect are the ones carrying the fuel.

This is why the Moorland Association is sceptical of the claim that rewetting, on its own, prevents wildfire. Rewetting raises water tables and stores carbon. It does not remove the standing dead vegetation that fires actually burn. The Tay reed beds were about as wet as a British habitat gets, and a quarter of them still went up in a single day.

The evidence-led position is straightforward. Rewetting and active fuel management are not competing choices. Rewetting manages hydrology. Controlled burning and cutting, where possible manage the fuel load and maintain the breaks that stop a fire spreading.

Drop the second and you are left with a wet site full of dead material and nothing to slow a fire once it starts — which is precisely what happened on the Tay. The RSPB, which manages half the reserve, said they would look at fire breaks and a site wildfire code for exactly that reason.

The bottom line for land managers

A site's protection from wildfire comes down to fuel management, whatever the ground's wetness. Someone keeps the fuel load down, and that is what keeps it safe.