The Wildlife Trust warns there is a serious risk of fire in the countryside this bank holiday weekend, after the prolonged spell of dry weather.
There have already been wildfires in different parts of England, which have killed animals and destroyed large swathes of nature reserves.
It is urging people to pack picnics and not BBQs amid predicted rising temperatures.
Scottish firefighters on high alert have asked people to "act responsibly".
"Our landscapes are under more pressure than ever", said Rob Stoneman from the Wildlife Trust.
"We are in a climate and nature emergency."
Rising temperatures and changing weather patterns mean landscapes "are more susceptible to wildfires", the director of landscape recovery said.
In the last month, about 60 firefighters tackled two large scrubland blazes in Surrey and homes were evacuated after a large fire was started deliberately at Canford Heath in Dorset.
"It was devastating to see almost half of this rare heathland burnt to a crisp", said James Herd from Surrey Wildlife Trust.
He said birds, snakes, lizards and heath tiger beetles "perished in the flames".
With the risk of wildfires being "very high" and forecasters predicting temperatures rising to 17 degrees, the Scottish Fire and Rescue Service has been put on high alert.
"With rising temperatures this weekend, and further dry conditions into next week, wildfires could burn and spread with very high intensity in high-risk areas", said group commander Niall MacLennan.
He said recent wildfires - such as on Ben Lomond and near Mallaig - show how "real the danger of fire is... and how damaging it can be to the environment".
The fire service has asked people to "act responsibly" and "think twice before using anything involving a naked flame".
The warning, put in place from Friday, is at very high until Monday for wildfires in central and north east areas in the nation and until Wednesday for central and southern Scotland.
"Too often a carefree day out can turn into tragedy when wildlife and precious habitats are devastated by wildfires caused by careless behaviour", said Mr Stoneman.
A long dry period has left many moorlands and grasslands "tinder dry" which means they could catch alight with a small spark, the Wildlife Trust explained.
It has asked people to pack picnics and not BBQs, extinguish all cigarettes and matches and to call emergency services if they spot any signs of fire.