Campaigners fear wildfires could "devastate local wildlife" after the latest in a series of blazes to hit nature reserves.
A fire at Bovey Heathfield nature reserve in south Devon on Wednesday followed another which ripped through a Cornwall reserve on Monday.
Wildfires, some started deliberately, have hit reserves and heathlands.
A three-mile (5km) wide fire that broke out on a moor near Bodmin, Cornwall on 11 February is being treated as arson.
Four large gorse fires broke out in Cornwall over a March weekend, two of which are thought to have been started deliberately.
Devon Wildlife Trust fears for breeding animals as lockdown rules are relaxed.
"At this time of year, birds are nesting, reptiles and insects are emerging and wildflowers are beginning to bloom," said Steve Hussey from the trust.
"The timing really couldn't be any worse."
The trust said people had been having barbecues and open fires at another reserve, Meeth Quarry near Hatherleigh in north Devon.
"A very dry spring means that our countryside is extremely vulnerable to fire," said Mr Hussey.
"All it needs is a discarded cigarette, a barbecue or spark from a fire pit and a large wildfire could ignite.
"The results of this can be devastating, not only for local communities, but for wildlife too."
The trust is also urging people to consider wildlife which have been disturbed by dogs not on leads and motorcyclists.
"We recognise that people are increasingly looking for green spaces for leisure activity on their doorsteps," he said.
"But our reserves are not playgrounds or parks and need to be enjoyed a little differently."