Wildfires plague the forested areas of Guam every dry season despite the island's humid climate. Most fires are caused by humans with 80% resulting from arson. Poachers often start fires to attract deer to the new growth. Invasive grass species that rely on fire as part of their natural life cycle grow in many regularly burned areas. Grasslands and "barrens" have replaced previously forested areas leading to greater soil erosion. During the rainy season, sediment is carried by the heavy rains into the Fena Lake Reservoir and Ugum River, leading to water quality problems for southern Guam. Eroded silt also destroys the marine life in reefs around the island. Soil stabilization efforts by volunteers and forestry workers (planting trees) have had little success in preserving natural habitats.