He attributed the drought to massive deforestation. At least 26 million rai (4.2m ha) of forested land, especially forests in the mountainous north, had been denuded, according to the prime minister, who said that forests were needed for the generation of rainfall. In July 2015, a "Bangkok Post" editorial summed up Thailand's forestry issues: "Forests have rapidly declined under state policies over the past four decades. Factors include logging, mining, anti-insurgency strategies, promotion of cash crops on the highlands, construction of big dams and promotion of the tourism industry. Corruption is also deep-rooted in forestry bureaucracy." Valuable hardwood tree species, such as Siamese Rosewood, are being extracted illegally for sale, mostly to the Chinese furniture market. These trees are so valuable that poachers are armed and are prepared fight forest rangers. Both rangers and poachers have been killed in gunfights. The rates of logging now threaten the Siamese Rosewood with extinction within 10 years, according to "Al Jazeera" in 2014. Deforestation creates a host of environmental problems: soil erosion, sedimentation of rivers, and loss of natural habitat. Wetlands and mangroves in coastal areas have been seriously degraded by expansion of commercial fishing, shrimp aquaculture, industry, and tourism, causing much of Thailand's biodiversity losses. It is estimated that Thailand in 1961 had 3,500 km2 of mangrove forests. By 2004 that number was less than 2,000 km2 according to the Thai government. According to Thailand's deputy transport minister, some of Thailand's attractive beaches may be lost within ten years. "If we don't do anything, there will be no attractive beaches left", he said. The marine department, part of the transport ministry, manages Thailand's 3,000 km of shoreline in 23 coastal provinces. Some 670 km of shoreline exhibits severe erosion, with land being lost to the sea at a rate of more than five metres per year. To combat erosion, sections of Pattaya Beach in Chonburi Province are being topped up with more than 300,000 m3 of sand at a cost of 429 million baht. A two kilometer stretch of Chalatat Beach in Songkhla is being restored at a cost of 300 million baht. The World Bank estimates that deaths in Thailand attributable to air pollution have risen from 31,000 in 1990 to roughly 49,000 in 2013. Industrial growth has created high levels of air pollution in Thailand.