Mining can be an intensive process and has affected some wilderness areas, including national parks and wildlife reserves such as Kahuzi-Biega and the Okapi Wildlife Reserve, both of which are world heritage sites. Mining in these areas is typically artisanal; a small-scale mining method that takes place in river beds and can, cumulatively, be very environmentally damaging. Artisanal mining degrades riparian zones, creating erosion and heavy silting of the water. The tailings are often dumped into the rivers and can be contaminated with mercury and cyanide degrading the health of the river systems and putting people and wildlife at risk.