The Beriev Be-200ES amphibious jet aircraft sustained damage when it hit the tops of trees while fighting a forest fire near S?o Pedro do Sul, Portugal. The aircraft had recently arrived in Portugal and was operating on the first mission. After departure from Monte Real Air Base the aircraft proceeded to a lake called Albufeira da Barragem do Vilar. Close to the Vilar Dam the aircraft scooped water. En route to a forest fire, the crew spotted a developing fire near S?o Pedro do Sul. The aircraft made a spiraling descent and dropped the water load while descending along downsloping terrain. As the aircraft flew through the smoke clouds, it contacted trees. The crew noted a loss of engine power and decided to return to Monte Real Air Base where an uneventful landing was carried out. On the ground it was noticed that the aircraft had sustained damage to the leading edges of both wings. Also, the right hand wing flaps sustained dents and cuts and the right hand wing float suffered a large hole.