BORDEAUX, France—The wildfire began on an usually dry summer day in a forest bordering the Liber Pater vineyard. Winemaker Loïc Pasquet saw the flames rise and spread toward his precious vines, which produce Bordeaux that sells for $30,000 a bottle. Hours before evacuating Mr. Pasquet and his staff destroyed the grass around the vineyard to prevent it from catching fire and dug trenches to block the blaze’s path. He also sprayed local trees with water drawn from the vineyard’s ponds. The vineyard was spared.

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