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Exploring the consequences of forest fires
Severe forest fires cause great damage: The forest temporarily loses its protective function, flora and fauna are destroyed, and settlements and traffic routes are exposed to increased erosion and rockfall. Less known are the positive consequences: The diversity of plants and animals after a forest fire increases rapidly, and after just a few years exceed the diversity of the forest previous to the fire.
The 2003 forest fire above Leuk (in the canton of Valais) is one of the most studied and documented in Europe. Scientisits showed that certain tree species quickly rejuvenate after a fire through resprouting and seed germination, eliminating the need for planting trees. After a period of time, the number of animal and plant species even exceeds that of an intact forest. The temporary, sparse forest structure, as well as the short-termed improvement of the nutritional conditions after a fire, benefits the living conditions for many animals and plant life.
This effect is dependent on the type and frequency of the fire (fire regime). With frequent and intense fires, the only species able to survive are species that have adapted to fire, so-called pyro-resistant species. On the other hand, living conditions change because of the forest fire, this being conducive to the spread of new species. How an area affected by a forest fire develops ultimately depends on the fire history.
Erosion, rockfall and other hazards
Forest fires blazing on steep slopes often cause rockfalls. When leaves and humus layers burn, destabilized rocks begin to roll. Worse effects occur after the fire: the fire usually leaves behind a thin to heavy layer of ashes that repels water. Rainwater can hardly seep into the ground for one to two years, resulting in surface runoff. This is how erosion begins, especially during heavy rainfall. Prolonged heavy rain can then lead to mudslides.
Support in decision-making
Subsequent to the extensive forest fire in Leuk, the WSL summarized the various research findings in a brochure, offering foresters and cantonal representatives support in decision-making, and also providing information on what measures should be taken after a forest fire.