Hill people

Hill people, also referred to as mountain people, is a general term for people who live in the hills and mountains. This includes all rugged land above 300 metres (980 ft) and all land (including plateaus) above 2,500 metres (8,200 ft) elevation. The climate is generally harsh, with steep temperature drops between day and night, high winds, runoff from melting snow and rain that cause high levels of erosion and thin, immature soils.

People have used or lived in the mountains for thousands of years, first as hunter-gatherers and later as farmers and pastoralists. The isolated communities are often culturally and linguistically diverse. Today about 720 million people, or 12% of the world's population, live in mountain regions, many of them economically and politically marginalized. The mountain residents have adapted to the conditions, but in the developing world they often suffer from food insecurity and poor health. They depend on crops, livestock and forest products, and tend to be poor. In the developed world the mountain people are generally prosperous, and the mountains may be used for tourism and outdoor recreation. Mining is also widespread and dates back to the pre-Christian era.

In parts of the developing world the mountain communities depend on remittances from young men who have gone to work in the lowlands or overseas. Although 70% of mountain people live in rural areas, the rest live in cities, including large cities such as Mexico City, with a population of around 21 million. The cities attract temporary or permanent migrants from the rural areas. The smaller cities are more connected to the mountain culture and economy than the larger ones.

Under the World Conservation Monitoring Centre (WCMC) classification, mountain regions include both hills and mountains. See "Classes of mountain region" for the formal definition. 22% of the world's land, or 29,000,000 square kilometres (11,000,000 sq mi) is classified as a mountain region, of which about half is below 1,000 metres (3,300 ft). Rugged land is considered a mountain region if it is at least 300 metres (980 ft) above sea level, but plateaus and broad valleys running through the mountains below 2,500 metres (8,200 ft) are not considered mountain regions. All land above 2,500 metres (8,200 ft) is classified as mountain, including plateaus. This accounts for 20% of the total. Mountain regions in a 2003 study by the Food and Agriculture Organization (FAO) of the United Nations follow the WCMC classification.

Mountain environments vary depending on their latitude and their proximity to the edge of a landmass. The windward side will have greater rainfall than the leeward. The mountain environment can be harsh, particularly in the alpine regions above the tree line at higher elevations and in the drier climates outside the tropics. No more than 3% of world's land that is highly suitable for agriculture lies in the mountain regions.

Temperatures tend to always be high on the lower slopes near the equator, and there is often heavy rainfall year-round. Higher up and outside the tropics, temperatures can soar in the daytime and plummet at night. Usually there are strong winds, frequent freezing and thawing at the higher levels, snow, sleet and heavy rainfall in some areas, causing steady erosion. The thin soils on the slopes do not retain water, and only support drought-resistant plants. Often these plants are low and store energy in spreading roots, with relatively little vegetation above ground. This vegetation may be cleared for cultivation or road building, or may be overgrazed, resulting in rapid soil loss through erosion.

People have both adapted to mountain conditions and modified those conditions. For example, farmers in many areas use terracing to retain soil and water. Contour ploughing also helps stabilize the fragile soil. Often human activity has degraded the mountain environments. Humans have reduced biodiversity in many of the world's mountain regions. Areas with high biodiversity where the environment is under intense stress include California's montane ecoregions (California montane chaparral and woodlands), the mixed forest ecoregion in the Caucasus, and in northwest South America the Magdalena Valley montane forests, Magdalena–Urabá moist forests and Western Ecuador moist forests.

Almost 28% of the world's forests grow on mountains. Forests are important in regulating water flows and providing fuel and construction material. Before humans arrived, most mountains in tropical and temperate climates would have been forested up to the tree line. Deforestation is not new, and began 3,000 years ago in China. Mountain forests around the Mediterranean and in Britain had been cleared 1,500 years ago. More recently, in China and Europe there have been efforts to restore the mountain forests so as to reduce flooding and erosion.