Status of land most vulnerable to sand encroachment
Land most vulnerable to sand encroachment is a kind of degraded land between sand encroachment and non-sand encroachment due to over utilization of land or shortage of water resource, tte area of land most vulnerable to sand encroachment is 318 600 km2, accounting for 3.32% of the total country's territory, which is mainly distributed in 4 provinces (autonomous region) including Inner Mongolia, Xinjiang, Qinghai and Gansu.
Dynamic Changes of Desertification
Compared with 1999, the national desertified land area decreased by 37,924 km2, representing an annual drop of 7585 km2. In terms of different desertification types, the area of desertified land caused by wind erosion decreased by 33,673 km2, by water erosion decreased by 5525 km2, while that of desertified land caused by salinization increased by 930 km2. In terms of desertification degree, the area of lightly desertified land increased by 90,700 km2, moderately desertified land increased by 117,300 km2, while that of severely desertified and and extremely severely desertified lands decreased by 131,700 km2 and 114,200 km2 respectively. As for major provinces, the area of desertified land in 16 provinces has decreased.
Development and Causes of Desertification in North China 18.3.1
Development and Cause Analysis 22.214.171.124
Before the term desertification was defined, Chinese scientists were more concentrated on sandy desertification caused by wind erosion. Researches showed that in the Pleistocene about 10 thousand years ago, several kinds of severe and frequent climatic oscillations happened in China, the occurrence and reversion of desert were mainly controlled by global climate change driven by earth orbital parameters. Since the Holocene, especially recent 2000 years, due to the increase of population, innovation of productive tools, and increase of the extension and intensity in farming, human activities gradually became another important factor. However, sandy desertification was still primarily caused by climate change. In the last one hundred years, the process of sandy desertification was affected by not only climate change, but also the intensified human activities (Dong et al. 1998). For exemple in Gonghe Basin of Qinghai province in China, during the 50s to 80s of 20th century, the accumulated afforestation and conservation area was 1,700 ha, but the destructed forest area was five times this area, and the expansion area of desertification even up to 32 times this area (Dong et al. 1998).
Type ofhuman activities
In North China, where wind erosion is the main factor affecting desertification, various human activities operated, including overgrazing (30.1%), excess reclamation (26.9%), excess firewood gathering (32.7%), irrational use of water resource (9.6%) and lack of environmental protection in building factories, mines and transportations (0.7%). In the southeast of Horqin grassland, which once was sparse forest grassland, 1,333 square kilometer ground were cultivated once, some of them even two or three times during the last one hundred years, tte percentage of shifting sand area occupying total land increased from 14% in late 1950s to 32% in 1970s. In late 1980s and 1990s, it was up to 41.2% and 54% (Zhu 1998).
Key vulnerable region tte most severe area of desertification in Northern China is farm-pastoral transition zone and rainfed agriculture area with annual precipitation of 200 mm- 400 mm and annual evaporation of about 2000 to 2500 mm. Since the region is at the edge of East Asia monsoon, there is vulnerable environment and sensitivity to climate change, resulting from low rainfall, arid climate, loose soil, and frequent high wind. During early 1950s to late 1970s, as a result of excess reclamation and firewood gathering, desertification developed further including acceleration of wind erosion of sandy grasslands and increase in the area of shifting sands. Until late 20th century, it began to reverse in most area according to the monitoring results from remote sensing. An example is Xijingzi village in semi-arid area which belonged to Shangdu County in Inner Mongolia where sandy desertification area made up about 41.3% of whole region in the early 1960s, and then jumped to 57.8% in 1978. Owing to adjustments in land use and countermeasures, the percentage dropped to 22.7% in late 1980s.
tte climate shifted to warm and dry in these areas. However, great changes in land use have been taken place since 1980s. So it could be found that environmental changes resulting from climate change provided a basis for desertification in farm-pastoral zone; but improper land use leads and accelerates its formation and development.(Xue et al. 2005; Li and Lu 2002). It is obvious that desertification in semi-arid and semi-humid areas in China during modern time is due to complicated interactions among climate change, human activities and desertified land under vulnerable ecosystems. (Dong et al. 1998).
Possible influence of climate change on desertification
Future climate change would continue to influence the development and adverse processes of desertification. On the basis of meteorological data at national level, the influences of climate change on desertification in China were estimated by HADCM2 model (Ci et al. 2002; Ci 1994). tte results illustrated that if C02 doubled and temperature increased by 1.5°C in 2030, the desertification area would expand 184,023 km2. In 2056, another 175,024 km2 would be desertificated. According to estimates from statistical regression prediction model (Dong et al. 1997; Shang et al. 2001), rising temperature and decreasing precipitation would lead to further desertification expansion in the future 80 years in northern desertification land. Another research also indicated that the development process of desertification in North China would be rapid and severe during the first ten years in 21st century with climate change (Shang et al. 2001).
Moreover, recent studies made clear that during the future 10 to 50 years, temperatures might be higher by 1.9 to 2.3 °C, precipitation would increase by 19% in Northwest China (Ding 2002). It will be advantageous to control natural expansion and accelerate the adverse process of desertification. However, there are uncertainties in long-term climate change, and regional climate is also likely to change to warm and dry. ttus, the postive influence of increasing temperatures and precipitation on desertification should not be overestimated.
Desertification Monitoring in China 18.4.1
Indicator system for desertification monitoring and evaluation
In order to make clear the status and damage degree of desertification and to operate early warning, it is essential to establish a scientific indicator system for desertification monitoring and evaluation. In 1977 at the United Nation Conference on Desertification (UNCOD) held in Nairobi, a "Map of the World Distribution of arid Regions" at 1:25 million scale was prepared by FAO, UNESCO, WMO and UNDP together, and the global desertification was evaluated (Lu et al. 2000). Aimed at making desertification maps and evaluating desertification status, indicator system was paid more attention by many scholars and international organizations (Berry and Ford 1977; Reining 1978; FAO andUNEP 1984; Oldeman 1998; Marbutt 1986; Hunsaker and Carpenter 1990; Hammond 1995; Rubio and Bochet 1998; and Dregne 1999).
A series of indicators for sandy desertification evaluation was determined in China in the past (Zhu and Liu 1984). In recent ten years, more progresses were made in the studies of indicator system for desertification monitoring and evaluation (Wang 2003). According to the definition of desertification and its characteristics, an indicator system was developed consisting of four components: driving forces indicators, state indicators, impact indicators and control indicators (Wang
2003). It was pointed out that for national or regional level the first step is to develop a frame of indicator system at macroscopic level. On the basis of it, executable indicator systems could be established at different areas, tten relative data are gathered according to the indicator system to monitor and evaluate desertification (Wang 2003; Wu et al. 2005).
Desertification monitoring in China
National desertification surveys in the history ofChina
From 1994 to 1996, the State Forestry Administration (former the Ministry of Forestry) of China organized experts and technicians to investigate desert, gobi and sandy desertification land in whole country. China national maps of desertification land distribution at 1:1 million and 1:2.5 million scales were made in 1996 respectively, and China Country Paper to Combat Desertification was finished (Wang 2003).
tte second nationwide desertification survey was carried out in 1999. tte frame of indicator technical rules for desertification evaluation consists of 3 climate zones, six types ofland use and 4 desertification land types.
tte 3rd National Monitoring Survey for Desertification and Sand Encroachment was completed in 2004 under the auspices of the State Forestry Administration and with the involvement of such sectors as agriculture, water conservancy, environmental protection, meteorology and the Chinese Academy of Sciences, tte focused ground survey is combined with interpretation of remote sensing data, as well as application of GIS and GPS. About 156 million units of information was obtained based on investigation in 5.02 million sites. A National Geography Information Management System for Desertification and Sand Encroachment was established.
Content and mission of China's desertification monitoring
It consists of arid, semi-arid and sub-humid area, distributed generally in ten provinces belonging to North and West China and involving 270 counties. Key monitoring area was in farm-pastoral transitional zone occupying 82 counties of 9 provinces ofNorth China.
Contents ofmonitoring tte status of desertification land distribution and dynamic macroscopic data in arid areas for the state, provinces and typical regions are requested to be provided at definded times. And maps of desertification land distribution should be pre pared in a timely when needed. Countermeasures and suggestions for desertification combating are put forward based on surveys and analysis.
Monitoring classification system
It consists of determination ofland use type, desertification type and degree. 126.96.36.199
China's Desertification monitoringsystem ttere are three levels of desertification monitoring.
The China National Desertification Monitoring Centre
Its main task is to provide timely data (number, figure and image) to central government in making strategic policy and specific measurements for desertification combating and land protection, to provide dynamic decision-making and consultation on some key development regions and sensitive eco-regions.
It is in charge of province monitoring.
Desertification monitoring station
Sequential investigations and records of desertification area, type and degree are operated in the stations with representative zone, and then reported to sub-center and national center.
Monitoring techniques and construction ofinformation managementsystem
Main techniques ofmacroscopic desertification monitoring tte ground observations are taken at fixed sample lands at appointed times, tte sampling method, combined with ground investigation and 3S (remote sensing, GIS.GPS) techniques, is used to estimate desertification land area. Systematic sampling and percentage sampling method are used in estimation of desertification land area status and dynamic macroscopic monitoring. And aerial photograph and remote sensing monitoring techniques are more and more applied to large area desertification monitoring.
Construction ofmonitoring information managementsystem
A uniform information management system was established. It consists of database and application analysis models, ttere are various applied models such as of dynamic prediction, environment evaluation and desertification loss evaluation, tte desertification monitoring information system for nationwide and provinces were built respectively.
China's Key Forestry Programs on Combating Desertification tte essential strategy in combating desertification in China is to control structure and function of agro-forest complex ecosystem, rationally use water and land resources, so as to promote a virtuous cycle within ecosystem, tte emphasis is put on prevention and control of further desertification extension, especially for vulnerable eco-regions. At the national level, a number of key programs on sand encroachment prevention and control have been launched and implemented, such as the six major forestry programs, grassland protection and improvement program and small watershed integrated program (State ForestryAdministration 2005).
Program for converting cropland to forest/shrubbery
188.8.131.52 Background tte first objective is to halt cultivation in the area with severe soil and water loss, desertification, salinization and Karst rocky desertification, or low and unsteady yields, and the second is to seed up tree and grass under specific local conditions and restore vegetation.
Scope ofProgram Construction
In this program, 25 provinces and Xinjiang Production and Construction Group were involved covering 1897 counties, tte emphasis was put on West and Middle China. And the important arable land with high ecological function in riverhead region, steep slope land surrounding lakes, severe soil and water loss land, and severe windstorm areas are given priority. In all, 856 counties were determined to be key counties for program construction, occupying 29.9% of total national counties, and 45.1% of total counties involved in the program region.
Objectives andAssignmentofProgram Construction tte objectives and assignments by 2010 are fixed to achieve 14.7 million ha afforestation from arable land and 17.3 million ha afforestation from barren hills, to finish converting cropland to forest in slope land, and increase vegetation fraction by 4.5 percent.
Programme of Combating desertification in the wind sand sources areas affecting Beijing and Tianjin city
In order to mitigate the damage of wind and sand storm and build an ecological defense for North China, central government made decision to implement a programme of combating desertification in the wind sand sources areas affecting Beijing and Tianjin.
Scope ofProgram Construction ttis project region involves five provinces of Beijing, Tianjin, Hebei, Shanxi and Inner Mongolia with 75 counties in total, tte whole area of this project is 458 thousand km2, in which the area of sand encroachment is 101.2 thousand km2.
Countermeasures and objectives ttis project took comprehensive control measures mainly on forest and grass vegetation restore. It included conversion of cropland to forest, afforestation, agricul-turalmeasure includeing manual grass planting, aerial seeding, enclosure, grassland construction, seed base, grazing prohibition, warm shed building, as well as hydrlogical measure, such as riverhead project, water-saving irrigation project, small watershed comprehensive treatment, ttere will be eco-immigration with 180 thousand people.
Three-North Shelterbelt Programme and Shelterbelt Programme in upper and middle reaches of the Yangtze River
Three North Shelterbelt Program
In order to change the status of wind-sand damage and soil and water loss in Northwest, North and Northeast China, ttree North Shelterbelt Program started to be implemented in November 1978.
Scope ofprogram construction ttis program covers 551 counties in northeast, north and northwest China, with a total area of 4.069 million km2, i.e., 42.4% of China's total land area.
Construction contents and size tte program started in 1978, and will completed in 2050 with a projected life span of 73 years, including three phrases and eight period projects. A total of 35.08 million ha of plantation is expected to be established under the program. When the program is completed, forest fraction in ttree North area would increase from 5.05% to 14.95%, and sand-storm damage and soil-water loss would be controlled effectively, tte fourth period started in 2001.
Five Shelterbelt Programs for Upper and Middle Reaches of Yangtze River and other areas
Five shelterbelt programs started successively. It contains Shelterbelt Programs for Upper and Middle Reaches of Yangtze River, Coastal Shelterbelt Program, Ecological virescence project of plain, Ecological virescence project of Taihang Mountain, and Shelterbelt Program for Pearl River.
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