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M A I K V E S T E , J I A R O N G G A O, B A O P I N G S U N , S I E G M A R - W . B R E C K L E
Photo 1: Mobile sand dunes in the Tengger desert near the Yellow River (Inner Mongolia)
Desertification of drylands is a global problem
in both developed and developing countries.
Desertification affects human life on many
levels. China is one of the seriously affected
countries with vast areas of desertification.
Dust and sand storms are threats for drylands
as well as for megacities. Dust is transported
over vast distances. During the past decades
major measures to combat desertification
were established in the northern provinces.
Those include vegetation shelterbelts and
reforestation of desertified lands to reduce
soil erosion and to stabilize sand dunes.
D
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esertification in China is accelerating in the northern provinces,
stretching from the western border
to the capital (Figure 1). Centres
of desertification are Xinjiang,
Inner Mongolia, Tibet, Gansu,
Qinhai, Shannxi, Ningxia, and
Hebei province. The desertification belt is located in the arid and
semi-arid zone of China. Here the
desert margins are vulnerable to
inappropriate land-use and climate
change. The area of arid, semiarid
and dry sub-humid regions is
approximately 3.32 million km2,
of which 2.62 million km2 (79 %)
has been desertified. This amounts
to 27.3 % of China’s territory.
Human-induced desertification
has often completely destroyed
the natural vegetation cover. One
of the major threats for the entire
region, which is closely connected
with desertification, is sand and
dust storms from the Gobi desert
(see also contribution by Littmann
and the Map Insert in this issue)
and other regions with wind
erodible surfaces. These storms
periodically return in winter and
spring. Since the 1950s a drastic
increase in the occurrence of dust
storms can be observed. In the
1950s the number of dust storms
was only five per year whereas in
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the year 2000 in a 45 day period
alone eight dust storms were
recorded in Northern China.
On 5 May 1993 during such
a dust storm in Xinjiang, Gansu,
Inner Mongolia and Ningxia
provinces, 85 people lost their
lives, 31 people went missing and
264 were injured (Yang et al.
2001). 120,000 head of cattle were
killed. The damage by erosion and
land degradation as well as the
economic loss was immense. The
dust storms not only affect the
rural areas but also large cities like
Beijing. Their traces are spread
across the northern hemisphere.
It is estimated that the immediate
economic damage through desertification in Northern China, which
is the least developed part of the
People’s Republic, is more than
€ 500 million each year. This sum
does not include the ecological
impact and the loss of natural
resources. Those indirect damages
may be as much as two or three
times that of the direct damage.
Geographische Rundschau International Edition Vol. 2, No. 3/2006
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Photo 1–7: M. Veste
The Green Great Wall – Combating
Desertification in China
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Desertification not only causes
land degradation but affects local
ground water resources and rivers
as well. Soil erosion transports
tremendous amounts of silt to the
riverbeds. The Great River was
renamed the Yellow River after the
increased transportation of loessic
materials. Very often the rivers dry
out and the ground water table
drops down due to the overuse of
the water resources for irrigation.
Water shortage enhances desertification processes and the destruction of vegetation belts.
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Seite 15
Table 1: The status of desertification in China, 1999 and 2004
Combating desertification
in China
Wind erosion
Desertification
degrees
Area (km2)
1999
2004
1,873,100
1,839,400
gentle
540,400
631,100
Water erosion
264,800
259,300
mild
868,000
985,300
Salinization
172,900
173,800
strong
565,100
433,400
Freeze-thaw
363,400
363,700
serious
700,600
586,400
Source: data collected by the authors
several reforestation programmes
and promoted scientific research
on the desertification process and
how to combat it (Sun and Fang
2001). The “Green Great Wall
Plan” was launched in 1978 to
restore the vegetation in the northern provinces and to protect the
cities from sand and dust storms.
In 1991 the “China Desertification
Rehabilitation and Desert Reclamation Action Programme”
started to operate. It is one of the
major engineering projects to
stabilize the ecosystems in China.
Besides technical measures the
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In recent decades the Chinese
government has become concerned about the environmental
situation and has established
Area (km2)
1999
2004
Desertification
causes
Design: Gao and Sun
Figure 1: Desertification regions in China
The most affected areas are in the arid and semi-arid provinces in northern China
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M . V E S T E , J. G A O, B. S U N , S. - W . B R E C K L E
The Green Great Wall – Combating Desertification in China
Photo 2: Straw checkerboard reducing surface wind speed
Chinese Government has formulated and promulgated laws, policies and regulations regarding
the prevention and control of
desertification, such as the Forest
Law, the Law of Soil and Water
Conservation, the Water Resource
Law, the Law of Environmental
Protection, etc.
In the past years noticeable
progress is being made in reducing
desertification. In 2004 the total
area effected by desertification in
China was 37,924 km2 less than
in 1999 (Table 1). However, this
reduction amounts only to 1.4 %
of the total desertified area. Therefore combating desertification
still remains a challenge. The best
achievements were made in the
stabilisation of seriously effected
areas; here the reduction was
nearly 19 %.
Photo 3: Stabilised sand dunes at the Yellow River along the railway
Beijing-Lanzhou
Photo 4: Microbiotic soil crust on sand dunes in the Tengger desert
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Shifting sands are one of the
major problems of desertification
and land degradation in arid and
semiarid areas. Sand dune movement is a threat to irrigated
farmlands, villages, railways, highways and other infrastructure.
Sandy areas cover large parts of
China’s deserts from the hyperarid zones in the west to the semiarid regions in the east. Therefore,
most investigations focus on desertification processes and rehabilitation of sandy areas.
Highly mobile dunes are characteristic of the Tengger desert
(Photo 1). The average annual
precipitation at the southern edge
is approximately 180 mm and
varies between 80 and 300 mm
per year depending on the monsoon. The rainy season is between
May and September. The mean
temperature in July is 24.3 °C and
–6.9 °C in January.
Historic records show that
these regions were vegetated centuries ago. In 428 AD shrubs and
grasses covered the Mu Us sandland west of the Tengger desert.
However, the capital was already
buried due to desertification only
500 years after its establishment.
In recent times most of the dunes
are bare of vegetation and are
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Sand dune fixation
19.05.2006
highly mobile. Average wind
speed is around 3.5 m per second
primarily from a northwesterly
direction. The relatively high precipitation of more than 180 mm
per year should promote a vegetation cover, but it seems that the
frequent high wind speeds counter
the re-establishment of natural
vegetation.
Several experiments have
been made regarding sand dune
stabilization worldwide. Planting
methods are a traditional means
to control drifting sands and are
widely practiced. However, sand
dune fixation by vegetation is
only successful when wind speed
is greatly reduced and sand movement is minimized. For dune stabilisation a combination of wind
breaks, straw checkerboards and
planted shrubs is used (Photo 2).
In the first stage straw checkerboards are installed manually to
increase surface roughness and
decrease sand transportation.
An efficient straw checkerboard
is 10 to 20 cm in height and
1 x 1 m in size (Qiu et al. 2004).
The checkerboard can cause the
deposition of blown sand (including seeds) and decrease the sand
flow by more than 99.5 % (Figure
2). Since 1957 this system was
successfully tested in the sand
dunes of northern China to protect
the railway line from Baotou to
Lanzhou. In Shapatou the vegetation protection system is 16 km
long and 500 m wide on the
northern and 200 m wide on the
southern side of the railway.
Meanwhile the straw checkerboard is widely used for sand
dune fixation. However the installation and maintenance of the
checkerboard is labour intensive.
In the Tengger desert the low rainfall limits tree planting but promotes shrubs, grasses and herbs
(Photo 3). In the centre of the
checkerboards were planted mainly seedlings of Artemisia ordosica,
Hedysarum scoparium, Caragana
korshinskii, Eragrostis poaeoides
and Calligonum mongolicum.
Other plants, especially annuals,
became established naturally.
Most remarkable is the development of biological soil crusts on
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the stabilised sand surface between
checkerboards and shrubs (Photo
4). These biological soil crusts
(also called microbiotic, microphytic or cryptogamic crusts) cover the upper millimetres of topsoil.
They are build up by cyanobacteria, green algae, mosses, fungi
as well as lichens. Such biological
soil crusts can be found in many
arid and semi-arid regions. For
example, most parts of the Negev
sand dunes in Israel are covered
by cyanobacterial and soil lichens
crusts (Veste and Breckle 2000).
They are one of the first colonizers
of disturbed soils.
In the Tengger desert soil crusts
can be found on stabilized plots.
With time the composition of the
crusts changes and a succession
takes place. The first colonizers
are cyabobacteria which stabilize
the sand surface. In the later stages
mosses are able to grow (Figure
3A). The biological soil crusts are
important for soil development
and strongly influence hydrological processes (Veste et al. 2001,
Veste 2005). Several studies
showed that biological nitrogen
fixation by free-living and symbiotic cyanobacteria is a major
nitrogen source and contributes
up to 60 % into this nutrient-poor
ecosystem. The cyanobacteria
excrete exo-polysaccharids which
cause the soil and sand particles
to stick together. This enhances
surface stability and prevents wind
erosion of the sand surface.
On the other hand the biological soil crusts have negative effects
on seedling establishment and
on hydrological processes. In general crusting of soil surfaces limits
infiltration and increases runoff.
Upon wetting the biological soil
crusts absorb rainwater followed
by swelling of the silt and clayey
particles and biological elements.
This results in a decrease of pore
size and thus limits infiltration.
In the sand dunes near Shapatou
(Inner Mongolia), it could be
observed that moisture retention
by fine grain material influences
water infiltration to deeper depths
which may lead to a declining
number of deep-rooting shrubs
(Figure 3A). Mosses especially
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Figure 2: Relation between wind speed and sand fluxes
in a shifting sand dune area and a 1 x 1 m checkerboard
area. Note that straw checkerboards prevent sand flux
up to a wind speed of 6.25 m per second
Source : Qiu et al. 2004
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Figure 3: Cyanobacterial crusts and mosses (A) and vegetation cover with shrubs, grasses and other annuals on
mobile and stabilised dunes (B) near Shapotou (Tengger
desert), representing different surface ages (0, 12, 29,
37 years in 1993)
Note that mosses prevent water infiltration and reduce water availability
for deep rooting shrubs which decline over time
Source: Fearnehough et al. 1998
enhance this negative effect while
containing a high amount of fine
material.
Reforestation projects
The unsustainable use of forest
resources leads also to a shortage
of timber and trees for fuel wood
in China. How drastic the changes
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M . V E S T E , J. G A O, B. S U N , S. - W . B R E C K L E
The Green Great Wall – Combating Desertification in China
Photo 5: Forest shelterbelt around Beijing
in the forest cover in the last centuries have been can be demonstrated in the Loess Plateau.
The Loess Plateau is one of the
centres of the development of the
Chinese civilization. During the
Ming Dynasty (1368–1644) and
the Qing Dynasty (1644–1911),
the forestry coverage on the
plateau was around 15 %. In
1949 the forest cover had been
reduced to 3 % due to forest cutting and lumbering. Large-scale
soil erosion was the consequence.
Therefore, the re-establishment
of forest systems was a major
goal in China’s programme to
combat desertification.
One of the most efficient systems is planting trees and shrubs
to form shelterbelts (Photo 5). Tree
shelterbelts are one of the major
components in building a “Green
Great Wall”. These huge protective forest systems are set up to
conserve soil and water and prevent damage from desertification.
The major protective forest systems are:
• the “Three Norths” protective
forest system,
• the protective forest system in
the middle and upper reaches
of the Yangtze River,
• the coastal windbreak system
and
• the farmland shelterbelts in the
plains.
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Sanbei or “Three Norths”
protective forest system
The Sanbei shelter forest is one of
the largest re-forestation projects.
Sanbei means “Three Norths” and
refers to the provinces in northwestern, northeastern and northern China (Figure 1). It extends
4,480 km in length from east to
west, and is 400–1,700 km wide
from north to south covering
551 counties in 13 provinces and
accounting for 42 % of the total
territory of China. In these vast
areas the farmland suffers from
wind and sand damage which
amounts to 6.7 million hectares
(ha) making up 40 % of the total
farmlands in China.
In order to deal with such a
serious situation, the Chinese
government decided to launch the
“Green Great Wall” on a large
scale. In the first phase of the
project (1978–1985), an area of
6.06 million ha was planted, of
which 63.8 % is windbreak. The
forest coverage of the “Three
Norths” region reached by the end
of the first phase was 6.2 %. Since
the second phase (1986–1995) the
establishment of a network of
farmland shelters is combined with
the introduction of commercial
forestry. In this period the forest
cover increased to 7.9 %.
According to a survey about
12 % of desertified lands are now
completely under control of antidesertification measures, and
another 10 % of desertified lands
will be soon under control. It is
estimated that by the end of the
project in 2050 5.23 million ha of
tree plantations will have been
completed.
Farmland shelterbelt
A farmland shelterbelt was successfully established in the Horqin
sandy land in the semi-arid northeast of China. The Horqin sandy
land stretches over 42,300 km2
Photo 6: Planting of trees is important to improve the local climatic
conditions in the villages
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(area northeast of Beijing in
Figure 1) in the transitional zone
between semi-arid and the subhumid with annual rainfall between 315 and 490 mm. It receives
90 % of the precipitation in the
growing season between April and
September. In the past the Horqin
district was fertile farmland and
pastures. Its original vegetation
was steppe with typical grassland
vegetation. Dominant species of
this region include Stipa grandis,
Leymus chinensis and Agropyron
cristatum. Desertification took
place due to forest cuttings and
overgrazing, and the area was
renamed “sandy land”. The
sandy areas are threatening villages, fields and infrastructure.
Shelterbelts were designed to protect the villages against local sand
storms and to reduce soil erosion
(Photo 6). Mainly fast growing
poplar species, including native
species such as Populus pseudosimonii, P. simonii and some other
useful domestic and foreign poplar
species, including P. deltoides,
P. trichocarpa and P. nigra, are
used for construction of the shelterbelt (Photo 7). Also different
conifer species were introduced.
Several tree species originated
from Europe and North America
and lead to changes in species
composition.
Besides the functions of tree
shelterbelts for soil protection, the
newly established forests are also
important for timber production
and as a firewood source for local
markets. This is closely related
to commercial timber processing
and the establishment of rural
enterprises. Leaves of poplar, willow and Ulmus are used as forage
resources for animal husbandry.
In the Shanxi Provinces 40,000 ha
of Caragana shrubs were planted
to use as fodder for sheep grazing.
Nowadays, the Sanbei district has
turned into an important producer
of fruits, including apples, apricots,
chestnuts, Chinese red dates
(Elaeagnus), pears, seabuckthorn
(Hippophae) and walnuts. In
Hebei province viniculture and
processing were promoted. From
seabuckthorn more than 200 products are made for health foods,
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cosmetics and medicines. The fruit
production creates new jobs and
income for the local people.
Combating desertification
on the Loess Plateau
The Loess Plateau is a vast area
which extends around midstream
of the Yellow river (Figure 1),
occupying about 580,000 km2.
There are about 60 million people
living on the plateau and a large
number of them are forced to
live in poverty in caves (called
Yaodong). The Loess Plateau is
considered to have been formed by
an accumulation of a huge volume
of loess with a thickness of 50 to
100 m brought in to this region
from the northwestern deserts by
strong winds 1.2 million years ago.
In prehistoric times the area was
covered with rich vegetation, but
the increase in population since
the 11th century promoted deforestation and the development of
grasslands on a large scale. As a
result the balance of the ecosystems got completely lost, and the
region has been facing extreme
erosion problems (Photo 8).
The Loess Plateau has an altitude between 1,000 and 2,000 m
above sea level. The annual mean
temperature is between 4 and
7º C and annual precipitation
is between 300 and 450 mm.
60–70 % of the rainfall takes place
Figure 4: Effect of plowing, grazing and seeding variations on soil and water outflow in the Loess Plateau.
For grass seedings Stipa bungeana, Bromus inermis and
Panicum virgatum were used. Panicum reaches a height
up to 1.2 m, Stipa and Bromus of 20–25 cm
Source: Ichizen 2003
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between July and September in
the form of torrential rains causing
serious soil erosion. The annual
amount of soil erosion is one of
the highest in the world and is
said to amount to 1,100 to 9,600
tons per km2.
The growth of 20,000 plant
species collected inside and outside of China has been studied for
several years. They were seeded in
experimental fields. Most species
Photo 7: Shelterbelt with poplar trees in Inner Mongolia
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Seite 20
The Green Great Wall – Combating Desertification in China
Photo: S.-W. Breckle
M . V E S T E , J. G A O, B. S U N , S. - W . B R E C K L E
Photo 8: Soil erosion on the Loess Plateau
were not suitable. Several perennial grasses grew well. The adaptability of 197 grass species was
tested in pasture trials. 20 species
grew for five years after seeding
(Figure 4). Panicum virgatum
exhibited by far the most dense
plant cover and greatest height.
New projects are on the way to
reach again a closed vegetation
cover and to reduce erosion by
extensive plantings of trees, often
along new small terraces and by
seeding grasses.
Biodiversity and ecosystem
functioning – a perspective
It can be concluded that for a
shelterbelt design and the rehabilitation of drylands a specific
knowledge of natural ecological
processes is needed. The present
measures in place to combat desertification are focussed on the
rapid development of sufficient
20
shelterbelts to reduce soil erosion
as well as dust and sand storms.
However, monocultures of
only a few species will lead to a
decline in biodiversity, and they
are threatened by future climate
change, pests or herbivory. Even
worse the introduction of alien
species causes adverse effects in
every ecosystem. Therefore future
rehabilitation concepts need to
include the indigenous biodiversity
and the mechanisms of the ecosystem in order to create self-sustaining ecosystems. In China “go
with nature” will be a major challenge for the improvement of shelterbelts against desertification. ■
References
Fearnehough, W., M.A. Fullen, D.J. Mitchell,
I.C. Trueman and J. Zhang 1998: Aeolian
deposition and its effect on soil and vegetation changes on stabilized desert dunes in
northern China. Geomorphology 23,
pp. 171–182
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Ichizen, N. 2003: Vegetation recovery in loess
plateau in China. Global perspective in
range rehabilitation and prevention of desertification. In: 2003 Obihiro Asia and Pacific
Seminar on Education for Rural Development (ed. J. Takahashi) OASERD Obihiro
University, Japan, pp. 45–49
Li, Z. and W. Shi 2003: Analysis of water consumption of artificial sand-fixing plants and
simulation of ecological moisture fitness.
Israel Journal of Plant Sciences 51 (2),
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Li, X.-R., X.-P. Wang, T. Li and J.G. Zhang
2002: Microbiotic soil crust and its effect on
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China. Boil. Fertil. Soils 35, pp. 147–154
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and its effects on the environment. J. Arid
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M. Veste and W. Wucherer (eds.): Sustainable Land-Use in Deserts. Heidelberg, Berlin,
New York, pp. 357–367
Veste, M. 2005: The importance of biological
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Veste, M. and S.-W. Breckle 2000: Die Negev –
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Veste, M., T. Littmann, S.-W. Breckle and
A. Yair 2001: The role of biological soil
crusts on desert sand dunes of the northwestern Negev (Israel). In: S.-W. Breckle,
M. Veste and W. Wucherer (eds.): Sustainable Land-Use in Deserts. Heidelberg, Berlin,
New York, pp. 357–367
Yang, G., H. Xiao and W. Tuo 2001: Black
windstorm in northwest China – a case
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Authors
Dr. Maik Veste (see page 7)
Prof. Dr. Jiarong Gao and
Prof. Dr. Baoping Sun
College for Soil and Water Conservation,
Beijing Forestry University, 35 Qinghua East
Road, Haidan District, 100083 Beijing /
PEOPLE’S REPUBLIC OF CHINA
E-Mail: [email protected]
Professor Dr. Siegmar-W. Breckle
Lehrstuhl für Ökologie, Universität Bielefeld,
Postfach 10 01 31, 33501 Bielefeld /
GERMANY
E-Mail: [email protected]
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