Forest genetic resources / Projects / China
Background and objectives
Desertification in the Korqin area
Desertification in northern China
Desertification or land degradation in dry areas is a global problem that is expanding. It is the consequence of overgrazing, over cutting of woody vegetation and poor cultivation practices in areas of sensitive vegetation and soils. Desertification and the reduction or destruction of arable land has had a major effect in China, where most of the population remains rural. The most seriously affected regions are located in the 13 provinces and autonomous regions in the arid, semi-arid and dry sub-humid areas across northern China. Many national minorities, including Mongolians, Uygurs and Tibetans, inhabit the area. The area includes approximately 60% of the poor counties of China.
The Government of China estimates that the land area affected by desertification in China is approximately 3 000 000 km2, or about one-third of China's total land area. Desertification is reported to be expanding at an annual rate of 2 500 km2, equivalent to a loss of 5 000 million tonnes of topsoil. The total area affected by wind erosion is estimated to be over 1 600 000 km2.
In addition to the loss of productive crop land, there are some other critical problems associated with desertification. Water resources are diminishing, and many formerly permanent watercourses are now seasonal. Watertables are falling in many areas. The changing water regime contributes directly to degradation and loss of indigenous vegetation. Inefficient use of water resources for agriculture practices in the dry zones increases the risk of soil salinization. It has been reported that there are some 9 900 km2 of saline land countrywide as a direct result of poor or inadequate irrigation practices.
The Great Green Wall
To tackle the immense problem of environmental degradation and the ever-increasing loss of natural resources, since 1978 the Government of China has been implementing the Three-North Shelterbelt Programme, also known as the Great Green Wall, which involves a network of shelterbelts and tree plantations across the entire northern area of China.
One of the main objectives of the Three-North Shelterbelt Programme is to protect agricultural and pastoral land, as well as human settlements, from wind and water erosion. To achieve this, a combination of three thrusts has been developed: establishment of shelterbelts; introduction of improved land management; and desert and sand dune stabilization and reclamation.
The Three-North Shelterbelt Programme covers an area of 4 060 000 km2 - nearly 42% of the country's total land area. There are 170 million people living in the region, but, with the exception of Beijing, the population density of the region is fairly low in comparison with the country as a whole.
The Three-North Shelterbelt Programme is the largest afforestation programme in the world. It aims to establish 35 million ha of shelterbelt forests between 1978 and 2050. By then, the forest cover in the Three-North Region of China will have increased to 14% from the current 5%. So far, over 13 million ha of plantations have been established; 4.33 million ha of mountainous and highly degradable land have been closed and protected from grazing and fire; and 0.4 million ha of forests have been established by aerial seeding. As the Three-North Shelterbelt Programme progresses, only the land located in more arid and infertile sites will remain as the target for afforestation and rehabilitation. Of the established plantations, 60% are owned by individuals, 30% by the state and 10% by collectives.
Forest and shrub species used in the establishment of plantations under the Programme include poplars and pines, or a combination of trees, shrubs and grasses. About 2 million ha of the planted poplars now maturing, but there are problems associated with the proper utilization and marketing of the lumber and other timber products as the plantations have not been tended, and particularly have not been systematically pruned.
Initially, plantation survival in the Three-North Shelterbelt Programme was poor due to a failure to match appropriate tree species to site conditions, coupled with the relative lack of maintenance during the first project phase. Survival has improved greatly since then, although there are still some problems, including:
- poor matching of species and clones to site conditions;
- poor planting techniques and lack of maintenance, the latter related both to technical problems and to a system that pays;
- subsidies only for planting and not for maintenance;
- planting at too close a spacing, resulting in poor growth rates and higher costs.
The Korqin Sandy Lands
The project area is located in a semi-desertic environment with a continental climate. The Korqin Sandy Lands covers an area of 42 000 km2 and receives an annual rainfall of 300 to 500 mm, mostly in summer. The area is characterized by sandy soils, with a critically low content of organic material and a shallow groundwater table. Winters are long, and temperatures drop to -15°C in January, while the absolute minimum temperature can reach -33°C. There are about 140 to 170 frost-free days. Soils freeze to a depth of 160 cm, depending on local conditions, and stay frozen until higher spring temperatures bring a thaw. Winds and high temperatures in summer, typical of a harsh continental climate, raise potential evapotranspiration to 2 to 3 times that of rainfall received. Where drainage is poor, marshes result; these sites often become saline and alkaline and are less productive. Saline or alkaline areas can be found throughout the Korqin Sandy Lands, but they are mostly located in the northeastern part, where the Tongyu Branch of the Project is located. Animal husbandry is the traditional economic mainstay of the population, that originally was pure Mongolian. The total population of the Zhelimu League was 2.5 million in 1983, with a density of 41.5 persons/km2, with an annual rate of increase of over 3% during the period 1949-1983. The domestic animal population has increased more than six-fold during the same period.
History of Korqin
In early times, Korqin was not a semi-desert, but grassland with dispersed trees (savannah-type woodland), in transition between dense forest and the steppe zone. A rolling sand-sheet was deposited during the last glacial period (Würm, 12 000 years BP). During 10 000 years of vegetation growth, a thick dark topsoil developed. In historical times, the region has gone through several cycles of man-induced desertification and subsequent recovery when human pressure lessened. By the middle of the 10th century, Korqin had developed into a prosperous agricultural and grazing area. At the time of the Jin Dynasty in the 12th century, the forest had reportedly disappeared and the land was covered with sand. By the beginning of the 17th century, Korqin thrived again, but after the middle of the 19th century, with the Qing Dynasty pursuing a policy of reclaiming "wastelands", forests and grasslands were once again destroyed and bare soil surfaces succumbed to wind erosion. The fertile dark topsoil vanished and extensive dune fields gradually build up. The latest desertification period would thus have occurred during the last one hundred years. Overgrazing (by cattle, goats, sheep, camels and horses), clearing of land for arable agriculture, and overcutting of trees and shrubs in this vulnerable ecosystem have resulted in increasingly severe land degradation and desertification.
Little remains of what was once the natural vegetation in the region. Some relics of poplar (Populus simonii), willows (Salix matsudana, S. gordejevii and other species), wild peach (Prunus armenaica) and elm (Ulmus pumila and other species) can still be found. A nature reserve, named Daqinggou ("Great Green Valley") in southern Korqin survives, with a rich mixture of tree and shrub species (Quercus mongolica, Fraxinus mandschurica, Tilia amuriensis, Acer truncatum, Juglans mandschurica and Crataegus pinnatifida) and many other woody plants and grasses.
Tree growth in Korqin is largely dependent on the presence of a high watertable, fed by percolation and inflow from the western and southern mountainous areas. There is long-term trend of a falling groundwater level due to increasing demand for water to irrigate crops and for human and industrial needs. There is a sound argument in favour of enhancing the soil's capacity for percolation of rainwater and for diminishing runoff. Wind erosion is obvious and most pronounced in spring, when sandstorms are common and vegetation is still absent or dormant after severe winter temperatures.
Soil fertility, already critically low, has shown a sharp decline as all organic residues from crops are removed for fuel and fodder during winter. Willow and poplar stands are pollarded in autumn, before leaf fall, for the same purpose. The continuous removal of potential soil nutrients is not balanced by the relatively small amounts of manure and inorganic fertilizer applied to crops. This has serious implications for future productivity and sustainability. Unfortunately, no data on long-term yield trends are available.
The southwestern Korqin area has reached a stage of severe desertification, while, in the other areas, water and wind erosion continue unabated, causing serious land degradation year after year.
FAO. 2002. Technical project review document. Rome.