the region's valuable timber reserves. The region was densely forested with stands of foremost Sal. Heavy logging began in the 1920s. Extracted timber was exported to India to collect revenues. Cleared areas were subsequently used for agriculture. But still, the Terai jungles were teaming with wildlife. Inner Terai valleys historically were agriculturally productive but extremely malarial. Some parts were left forested by official decree during the Rana dynasty as a defensive perimeter called Char Kose Jhadi, meaning 'four kos forest'; one kos equals about . A British observer noted, "Plainsmen and paharis generally die if they sleep in the Terai before November 1 or after June 1." British travelers to Kathmandu went as fast as possible from the border at Raxaul to reach the hills before nightfall. Malaria was eradicated using DDT in the mid-1950s. Subsequently, people from the hills migrated to the Terai. About 16,000 Tibetan refugees settled in the Nepal Terai in 1959–1960, followed by refugees of Nepali origin from Burma in 1964, from Nagaland and Mizoram in the late 1960s, and about 10,000 Bihari Muslims from Bangladesh in the 1970s. Timber export continued until 1969. In 1970, the king granted land to loyal ex-army personnel in the districts of Jhapa, Sunsari, Rupandehi and Banke, where seven colonies were developed for resettling about 7,000 people. They acquired property rights over uncultivated forest and 'waste' land, thus accelerating the deforestation process in the Terai. Between 1961 and 1991, the annual population growth in the Terai was higher than the national average, which indicates that migration from abroad occurred at a large scale. Deforestation continued, and forest products from state-owned forest were partly smuggled to India. Community forestry was introduced in 1995. Since the 1990s, migration from the Terai to urban centres is increasing and causing sociocultural changes in the region. Politics Since the early 1950s, several political parties advocated for autonomy and independence of the Nepal Terai, such as the Nepal Terai Congress and Janatantrik Terai Mukti Morcha. Several armed groups were formed, which pursued this aim using violent means. In 2013, more than 24 Madheshi political parties were registered for the Constituent Assembly of Nepal election. Border disputes The most significant border dispute of the Indo-Nepal boundary in the Terai region is the Susta area. In the Susta region, 14,500 hectares of land is generally dominated by Indian side with support of Sashastra Seema Bal (Indian border patrol)