Internationally important chalk grassland has been damaged in two heath fires at a Dorset nature reserve.
Both fires broke out on land owned by the National Trust on the Isle of Purbeck on Tuesday. One was at Harmony Farm, near Godlingston Heath.
The second incident was at Ballard Down. The trust said they may have been started deliberately but police investigations were continuing.
It added that it was too early to assess the impact on the wildlife.
David Hodd, countryside manager for the National Trust on Purbeck, said: "It is fair to say it [the full extent of the damage to the heathland] will be significant.
"Once our teams can begin surveying it in the daylight, we will have a clearer idea of the impact of these fires."
Purbeck contains more plant species than any other part of the UK.
The area damaged on the Isle of Purbeck is a Site of Special Scientific Interest (SSSI), National Nature Reserve and Special Area of Conservation.
It is one of the few places in Britain where all six native reptiles are found, including the smooth snake, adder and endangered sand lizards as well as several rare species of birds, butterfly and invertebrates, the trust added.
However, it is not the first time the reserve has been damaged by fire.
In May 2007, a carelessly discarded cigarette is thought to have started a fire which devastated more than 2.5 hectares (six acres) of Godlingston Heath.
More than 500 sand lizards are thought to have died in the fire, or as a result of losing their habitats and being exposed to predators, a spokesman for the trust said.
"It is estimated the heath [damaged in 2007] could take up to 30 years to recover from that fire, and we are not yet sure, but it looks like [yesterday's] may have affected an even larger area," added Mr Hodd.