Breeding stocks, population reservoirs
Natural areas provide support systems for commercially valuable environmental benefits and resources. Some habitats protect crucial life stages or elements of wildlife populations that are widely and profitably harvested outside these habitats, such as spawning areas in mangroves and wetlands. For example, when mangrove areas are cleared for resort and urban development, populations of commercial fish species that rely on mangroves for breeding habitats, also diminish. Therefore, some of these crucial habitats have been declared protected areas, due to their importance for maintaining stocks of fish and other aquatic fauna. (Olsen, 1977; Ivanovici, 1983).
In Croatia, the existence of the reservoirs is crucial for the large biodiversity on Cres island, and contributes to the preservation of the Griffons. The griffon colony can only survive as long as the sheep on the island are reared in the traditional, extensive way, which assumes the existence of reservoirs with drinkable water.