A wildfire near Britain’s biggest nuclear power station has caused “total devastation” to one of the UK’s most important landscapes, experts have warned, as fire crews said the situation is “stabilising”.

More than 100 firefighters have been battling the blaze in Dunwich Heath, near Leiston, on the Suffolk coast since Wednesday evening. The fire service said on Friday the situation is stabilising but is still being described as a “major incident”.

Firefighting efforts have included a helicopter capable of dropping 1,000 litres of seawater on each pass and six London fire brigade appliances.

The fire has torched approximately 150 hectares of vegetation and forest at Dunwich Heath and the Minsmere nature reserve, which are both protected sites that are home to some of the UK’s rarest species.

Russell Clement, the general manager for the National Trust on the Suffolk Coast, said the fire has “torn through” the Dunwich Heath National Trust reserve.

Clement said the reserve is now “unrecognisable” and the fire has caused “total devastation” to one of the UK’s most important coastal healthland landscapes.

Adam Rowlands, the area manager for the RSPB Minsmere nature reserve, said it will probably take decades for the vegetation to be established in the way it was before the fire.

The reserve is home to some of the rarest birds in the UK including species such as nightjars, nightingales and Dartford warblers. Rowlands said he saw nightjars flying away from a 20ft fireball.

He said any bird species that had survived the fire were “likely to perish” because they would not be able to find a suitable habitat to feed and breed in.

The wildfire came as half of England was declared to be officially in drought, including East Anglia and six other areas. On Thursday, Natural Resources Wales declared a drought across the whole of Wales, which is on course for its driest July since records began nearly 200 years ago.

As most of Europe experienced its fourth heatwave of the summer, intensified by the burning of fossil fuels, fire crews in other parts of the UK tackled multiple wildfires this week.

About 50 firefighters are tackling a blaze that broke out on Ministry of Defence land in Middlewick Ranges, Colchester. Essex county fire and rescue services said on Friday morning: “The fire is surrounded. Firefighters are working well extinguishing the fire. Please continue to avoid the area to help us keep the area safe.”

Crews in Scotland said they had made “significant progress” on the blaze, which first broke out two weeks ago in the Cairngorms, while several wildfires have broken out across Doncaster this week.

The Suffolk blaze is a few miles from Sizewell B nuclear power station and the construction site for the new Sizewell C plant.

Freddie Gulliver, an emergency manager at the Suffolk Joint Emergency Planning Unit, said there was no immediate concern about the fire spreading towards Sizewell B.

EDF said: “The fire at Dunwich Heath is not currently affecting operations at Sizewell B power station, but we are continuing to monitor the situation. We are not on high alert.”

About 50 people have been evacuated from their homes and a nearby holiday park, with some being moved to Westleton, where the village hall was turned into a rest centre.

Connor Dowsett, 23, who was told to leave Cliff House Holiday Park in Dunwich on Wednesday before his dog was rescued by officers, told the Press Association the fire felt like the “end of the world”.

Dowsett, who is from Essex, said: “We noticed the moon … it was very orange. As we were getting closer, we could see the glow of the fire. We could see the brown smoke filling the air. The smell was powerful. It was like ‘wow’.”

While it has not yet been established what caused this fire, Jon Lacey, the chief fire officer at Suffolk fire and rescue, advised residents to avoid using disposable BBQs, even in their own gardens.

“The ground is so dry at the moment and fires do start a lot more quickly than people expect,” he said.

According to the Met Office, Suffolk has only received 2% of its average monthly rainfall for July.

Lacy said the recent hot and dry weather has made this fire significantly worse.

“When the temperatures increase to around 28-plus degrees, that starts to become more of a challenge for firefighters because you’ll expect more incidents. If you then have a significantly prolonged dry spot, even if there are small showers, it doesn’t make a huge difference. And then if you add on to that the winds that we’ve had more significantly in the last few days, those three things can make quite a bit of difference to the fire spread,” he said.

Lacy said the changing climate is a key element of the fire service’s Community Risk Management Plan. “We know as it gets hotter that, as a fire service, we need to be prepared,” he said.

As most wildfires are caused by human activity, the Wildlife Trust said it is “vital that everyone follows official fire safety guidance, including: no BBQs, no cigarette butts, no littering.”

Jon Pearce, the Labour MP for High Peak, is calling on retailers across the UK to suspend the sale of disposable BBQs as the risk of wildfires continues to rise.

The prime minister, Andy Burnham, said Suffolk’s fire service would have “all of the support” it needed to tackle the wildfire.

The Green party leader, Zack Polanski, called for Burnham to host an emergency Cobra meeting to discuss wildfires across Britain, including the Suffolk blaze.