Mountains ecosystem, including Preah Monivong National Park, Botum-Sakor National Park, and the Phnom Aural Wildlife Sanctuary and Phnom Samkos Wildlife Sanctuary. The Worldwide Fund for Nature recognises six distinct terrestrial ecoregions in Cambodia – the Cardamom Mountains rain forests, Central Indochina dry forest, Southeast Indochina dry evergreen forest, Southern Annamite Range tropical forest, Tonle Sap freshwater swamp forest, and Tonle Sap-Mekong peat swamp forest. The rate of deforestation in Cambodia is one of the highest in the world and it is often perceived as the most destructive, singular environmental issue in the country. Cambodia's primary forest cover fell from over 70% in 1969 to just 3.1% in 2007. In total, Cambodia lost of forest between 1990 and 2005 – of which was primary forest. Since 2007, less than of primary forest remain with the result that the future sustainability of the forest reserves of Cambodia is under severe threat. In 2010–2015, the annual rate of deforestation was 1.3%. The environmental degradation also includes national parks and wildlife sanctuaries on a large scale and many endangered and endemic species are now threatened with extinction due to loss of habitats. There are many reasons for the deforestation in Cambodia, which range from opportunistic illegal loggings to large scale clearings from big construction projects and agricultural activities. The global issue of land grabbing is particularly rampant in Cambodia. The deforestation involves the local population, Cambodian businesses and authorities as well as transnational corporations from all over the world. Plans for hydroelectric development in the Greater Mekong Subregion, by Laos in particular, pose a "real danger to the food supply of Vietnam and Cambodia. Upstream dams will imperil the fish stocks that provide the vast majority of Cambodia's protein and could also denude the Mekong River of the silt Vietnam needs for its rice basket." The rich fisheries of Tonle Sap, the largest freshwater lake in Southeast Asia, largely supply the impoverished country's protein. The lake is unusual: It all but disappears in the dry season and then expands massively as water flow from the Mekong backs up when the rains come. "Those fish are so important for their livelihoods, both economically and nutritionally", said Gordon Holtgrieve, a professor at the University of Washington who researches Cambodia's freshwater fish and he points out that none of the dams that are either built or being built on the Mekong river "are pointing at good outcomes