The forest fires which have devastated large parts of Portugal could be followed by massive soil erosion, environmental campaigners say.
Portugal was worst-hit by the forest fires which swept across Europe after weeks of drought and heat.
Forestry officials estimated earlier in August that an area almost the size of Luxembourg had already been lost to the flames - around 215,000 hectares (531,000 acres).
The fires are now out, but Portugal's largest green campaign group says much of the damage is yet to come
"During the first rainfalls in the fall there will be a huge quantity of soil which will be dragged as sediment into bodies of water," said Francisco Ferreira, the vice-president of Quercus quoted by AFP news agency.
More than 12.5 million metric tons of topsoil will be eroded in the next year, the group says. Agriculture could be badly affected, and water supplies put at risk of pollution.
"If there are people who supply themselves with water from rivers and lakes, the quality of that water could be harmed if there is a strong rainfall which drags ash and sediment into it," said Mr Ferreira.
Quercus believes the final toll of lost woodland will be 250,000 hectares - with each hectare potentially shedding up to 50 tons of soil, it says.
The fires in Portugal claimed at least 18 lives, and damage is estimated by the government at nearly one billion euros. Many farmers have lost crops, land and livestock, while others have lost their homes. The final fires - near Monchique in the south and Castelo Branco in central Portugal - were brought under control on Saturday.

In Portugal's previous worst year for fires, 1991, around 182,500 hectares were lost. Forest fires have raged across Europe during the long summer heatwave, as far north as Sweden and as far east as Russia.
Firefighters in some countries, including Italy and Greece, have continued to battle blazes.

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