The environmental charity WWF has said it will take at least two decades for forests to grow back in the areas of Greece destroyed by the recent fires.
Large areas of southern Greece were badly burnt by the fires
Several rare animal species, including turtles, lizards and the golden jackal, were also affected, but it is too early to assess the damage, the WWF said.
The fires in August killed 67 people and engulfed nearly 200,000 hectares (494,000 acres) of countryside.
The Greek government has blamed arsonists for some of the wildfires.
The blazes came after two successive heatwaves in the region, during which temperatures reached 46C (115F).
'Mosaic of land'
A spokeswoman for the WWF, Panagiota Maragou, said the summer's fires had destroyed 173,000 hectares (427,500 acres) of rural land in Greece's Peloponnese peninsula.
More than half of that was made up of forests or protected nature reserves, while another 41% was farmland, she said.
"It was a mosaic of land that was affected - pine forests, olive groves and farmed fields," she said.
"We will have low vegetation in the beginning, but we won't have a forest before the end of a 20-year period and our generation will never see fir forests in these areas again."
Ms Maragou said some of the forests destroyed had not been affected by fires for more than a century, which she said could mean serious consequences for some rare animal species.
The charity also announced it was setting up a group of lawyers to intervene if developers try to take advantage of the disaster.
The government, which was returned to power with a reduced majority after the fires, has promised that the burned forests will be protected, but the WWF's Greece director said he was sceptical.
"We've heard these assurances before, and we've seen that development happen, and that's why... the WWF will be taking on a more active, more aggressive watchdog role in monitoring exactly what is happening and intervening, through legal experts, where that is necessary," Dimitris Karavellas said.
The BBC's Malcolm Brabant in Athens says local government officials in some of the burned areas want to encourage tourist development in order to replace agricultural economies that are now dead or fatally wounded.
They resent what they see as high-minded interference of prosperous city-dwellers, our correspondent says.
But the WWF insists that humans and nature can co-exist as long as there is sensible and sensitive sustainable development.