For a small country, Nepal has great physical diversity, ranging from the Tarai Plain -- the northern rim of the Gangetic Plain situated at about 300 meters above sea level in the south -- to the 8848-meter-high Mount Everest, locally known as Sagarmatha (its Nepali name), in the north. From the lowland Tarai belt, landforms rise in successive hill and mountain ranges, including the stupendous rampart of the towering Himalayas, ultimately reaching the Tibetan Plateau beyond the Inner Himalayas. This rise in elevation is punctuated by valleys situated between mountain ranges. Within this maze of mountains, hills, ridges, and low valleys, elevational (altitudinal) changes resulted in ecological variations.

Nepal commonly is divided into three broad physiographic areas: the Mountain Region, the Hill Region, and the Tarai Region. All three parallel each other, from east to west, as continuous ecological belts, occasionally bisected by the country's river systems. These ecological regions were divided by the government into development sectors within the framework of regional development planning.

The rhythm of life in Nepal, as in most other parts of monsoonal Asia, is intricately yet intrinsically intertwined with its physical environment. As scholar Barry Bishop learned from his field research in the Karnali region in the northwest, the livelihood patterns of Nepal are inseparable from the environment

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The Mountain Region (called Parbat in Nepali) is situated at 4,000 meters or more above sea level to the north of the Hill Region. The Mountain Region constitutes the central portion of the Himalayan range originating in the Pamirs, a high altitude region of Central Asia. Its natural landscape includes Mount Everest and the other seven of the world's ten highest peaks, which are the legendary habitat of the mythical creature, The Yeti, or Abominable Snowman. In general, the snow line occurs between 5,000 and 5,500 meters. The region is characterized by inclement climatic and rugged topographic conditions, and human habitation and economic activities are extremely limited and arduous. Indeed, the region is sparsely populated, and whatever farming activity exists is mostly confined to the low-lying valleys and the river basins, such as the upper Kali Gandaki Valley.

In the early 1990s, pastoralism and trading were common economic activities among mountain dwellers. Because of their heavy dependence on herding and trading, transhumance was widely practiced. While the herders moved their goths (temporary animal shelters) in accordance with the seasonal climatic rhythms, traders also migrated seasonally between highlands and lowlands, buying and selling goods and commodities in order to generate much needed income and to secure food supplies.

Situated south of the Mountain Region, the Hill Region (called Pahar in Nepali) is mostly between 1,000 and 4,000 meters in altitude. It includes the Kathmandu Valley, the country's most fertile and urbanized area. Two major ranges of hills, commonly known as the Mahabharat Lekh and Siwalik Range (or Churia Range), occupy the region. In addition, there are several intermontane valleys. Despite its geographical isolation and limited economic potential, the region always has been the political and cultural center of Nepal, with decision-making power centralized in Kathmandu , the nation's capital. Because of immigration from Tibet and India, the hill ranges historically have been the most heavily populated area. Despite heavy out-migration, the Hill Region comprised the largest share of the total population in 1991.

Although the higher elevations (above 2,500 meters) in the region were sparsely populated because of physiographic and climatic difficulties, the lower hills and valleys were densely settled. The hill landscape was both a natural and cultural mosaic, shaped by geological forces and human activity. The hills, sculpted by human hands into a massive complex of terraces, were extensively cultivated.

Like the Mountain Region, the Hill Region was a food-deficit area in the early 1990s, although agriculture was the predominant economic activity supplemented by livestock raising, foraging, and seasonal migrating of laborers. The vast majority of the households living in the hills were land-hungry and owned largely pakho (hilly) land. The poor economic situation caused by lack of sufficient land was aggravated by the relatively short growing season, a phenomenon directly attributable to the climatic impact of the region's higher altitude. As a result, a hill farmer's ability to grow multiple crops was limited. The families were forced to adapt to the marginality, as well as the seasonality, of their environment, cultivating their land whenever they could and growing whatever would survive. Bishop has noted that "as crop productivity decreases with elevation, the importance of livestock in livelihood pursuits . . . increases. For many Bhotia [or Bhote] living in the highlands . . . animal husbandry supplants agriculture in importance." During the slack season, when the weather did not permit cropping, hill dwellers generally became seasonal migrants, who engaged in wage labor wherever they could find it to supplement their meager farm output. Dependence on nonagricultural activities was even more necessary in the mountain ecological belt.

In complete topographic contrast to the Mountain and Hill regions, the Tarai Region, also called Madhesh , is a lowland tropical and subtropical belt of flat, alluvial land stretching along the Nepal-India border, and paralleling the Hill Region. It is the northern extension of the Gangetic Plain in India, commencing at about 300 meters above sea level and rising to about 1,000 meters at the foot of the Siwalik Range. The Tarai includes several valleys (dun), such as the Surkhet and Dang valleys in western Nepal, and the Rapti Valley (Chitwan) in central Nepal.

The word tarai, a term presumed to be derived from Persian, means "damp," and it appropriately describes the region's humid and hot climate. The region was formed and is fed by three major rivers: the , the Narayani (India's Gandak River), and the Karnali. A region that in the past contained malaria-infested, thick forests, commonly known as Char Kose Jhari (dense forests approximately 12 kilometers wide), the Tarai was used as a defensive frontier by Nepalese rulers during the period of the British Raj (1858-1947) in India. In 1991 the Tarai served as the country's granary and land resettlement frontier; it became the most coveted internal destination for land-hungry hill peasants.

In terms of both farm and forest lands, the Tarai was becoming Nepal's richest economic region. Overall, Tarai residents enjoyed a greater availability of agricultural land than did other Nepalese because of the area's generally flat terrain, which is drained and nourished by several rivers. Additionally, it has the largest commercially exploitable forests. In the early 1990s, however, the forests were being increasingly destroyed because of growing demands for timber and agricultural land.