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Why Large-Scale Afforestation Efforts in China Have Failed To Solve the Desertification Problem

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Abstract

T raditional Chinese approaches to ecosystem restoration have focused on affores-tation as an important tool for controlling desertification. However, the long-term results of this practice increasingly show that these projects are actually increasing environmental degradation in arid and semiarid regions, with ecosystems deteriorating and wind erosion increasing. Rather than focusing solely on affores-tation, it would be more effective to focus on re-creating natural ecosystems that are more suitable for local environments and that can thus provide a better chance of combating desertification. Arid and semiarid regions make up ~40% of the earth's land surface and are home to ~20% of the human population, but these areas are increasingly being affected by desertification (1). A half-century policy of forest exploitation, livestock overgraz-Trenches were dug parallel to the contours during planting to prevent downslope erosion and collect slope runoff for the trees. The decreased vegetation cover can offset this advantage by increasing wind erosion.
Interview
Traditional Chinese approaches to ecosys-
tem restoration have focused on affores-
tation as an important tool for controlling
desertification. However, the long-term
results of this practice increasingly show
that these projects are actually increasing environ-
mental degradation in arid and semiarid regions,
with ecosystems deteriorating and wind erosion
increasing. Rather than focusing solely on affores-
tation, it would be more effective to focus on re-cre-
ating natural ecosystems that are more suitable for
local environments and that can thus provide a bet-
ter chance of combating desertification.
Arid and semiarid regions make up ~40% of the
earth’s land surface and are home to ~20% of the
human population, but these areas are increasingly
being affected by desertification (1). A half-centu-
ry policy of forest exploitation, livestock overgraz-
© 2008 American Chemical Society
Why Large-Scale
Afforestation Efforts
in China
Have Failed To Solve the
DESERTIFICATION
PROBLEM
SH IX IO NG CA O
CH INA AGR ICU LTURAL UNI VERS ITY
Trenches were dug parallel to the contours during planting to prevent downslope erosion and
collect slope runoff for the trees. The decreased vegetation cover can offset this advantage by
increasing wind erosion.
WAT ER A ND S OIL C ONS ERV ATIO N IN STI TU TE, CHI NES E AC ADE MY O F SC IENC ES
1826 EnvironmEntal SciEncE & tEchnology / march 15, 2008
Planting trees in arid and semiarid regions of China
has led to increased environmental degradation
and impacts on soil moisture, hydrology,
and vegetation coverage.
ing (2), and monoculture planting of forests (often
to prioritize wood production) in China has led to
the disappearance of many natural forests and to
large increases in desertification (3). Currently, de-
sertification is concentrated in the northwestern,
northern, and northeastern parts of the country (the
so-called Three Norths): an estimated 3.3 million
km2 have been affected by desertification, account-
ing for 34% of China’s total land area (4).
The Chinese government first recognized the
problem of environmental degradation in these ar-
eas in the 1970s (5). As a result, since 1978 China
has pursued one of the most ambitious conservation
programs in the world—the Three Norths Shelter
Forest System Project—to prevent desertification
by carrying out large-scale afforestation in arid and
semiarid areas (6). The project will continue until
2050 and will involve 551 counties in 13 provinces,
covering a total area of 4.1 million km2 (42.7% of
China’s land surface). In the project area, 30.6 mil-
lion ha of afforestation is planned, at a cost of ¥4
billion ($1 ¥7.26 in January 2008). From 1978 to
2003, 23.5 million ha of grassland was planted with
trees (7). To decrease the damage caused to Beijing
by sandstorms created by desertification upwind of
the city, the Taihang Mountains Afforestation Proj-
ect in northern China, which began in 1999, will
cover 110 counties in Beijing, Hebei, Henan, and
Shanx i provinces, with plans to plant 3.6 million
ha of forest (an investment of ¥50 billion from 1999
to 2010). From 1999 to 2005, 2.6 million ha of grass-
land was planted with trees (8). Another large-scale
afforestation program, the Grain for Green Project,
plans to spend an additional ¥300 billion to convert
147 million ha of farmland on steep slopes (≥25°) or
with low yield and 173 million ha of grassland into
forest in 25 Chinese provinces from 1999 to 2010 (9).
By the end of 2003, 72 million ha of farmland and
79.3 million ha of grassland had been planted with
trees under this project, covering >70% of the area
of the Three Norths region (10).
In its scale, the number of participants, and the
magnitude of the investment, China’s afforestation
project is the largest ecological restoration program
in the world (1012). China’s government appears
to be making aggressive changes in forest-related
policies that formerly emphasized economic returns
(13). Accordingly, the focus of the new policies is on
how to grow more forests and how to shift from nat-
ural vegetation to planted forests. In this article, I
evaluate potential links between environmental
policy and environmental sustainability in China
by presenting a historical perspective on Chinese
afforestation projects. I provide a preliminary as-
sessment of their impacts in terms of soil moisture,
hydrology, and vegetation coverage.
Failure of large-scale afforestation efforts
Although average annual precipitation increased
and evapotranspiration decreased in response to
warming of the climate of the Three Norths region
from 1952 to 2005 (14, 15), 29.1% of China’s area (2.2
billion ha) was converted into forest by afforestation
(Figure 1) (8). Although the area of afforestation is
increasing rapidly as a result of the above-mentioned
projects, the area of degraded land has continued to
expand and the severity of desertification has con-
tinued to intensify throughout the country (16). This
suggests that these costly efforts have yielded little
success thus far; deserts in China have expanded
to cover an additional 1560 km2 of land every year
ma rch 15, 200 8 / E nvi ro nm En tal Sc iEnc E & tE ch no lo gy 182 7
from 1950 to 1975, 2100 km2/yr from 1976 to 1988,
and 3600 km2/yr after 1998 (4, 15, 17). Accompanying
this desertification, sandstorms have increased in
frequency and intensity in recent years in northern
China, from an average of 0.5 times per year in the
1950s to 10.3 times per year between 2000 and 2006
(Figure 2; 4, 1419). The impact of these sandstorms
is felt not only near the origins of the sand but also
in eastern China and areas beyond, including Japan,
South Korea, and North America (10). The economic
and social costs of this land degradation and associ-
ated disasters have been enormous. Sandstorms are
estimated to have caused more than ¥50 billion per
year in damage since 2000 (5).
Ignoring natural ecosystem characteristics
Drought is a major constraint worldwide to the pro-
duction of common vegetation types such as forests
(20), and revegetation of arid regions such as those
in China is primarily water-limited (21). In arid and
semiarid northern China, soil moisture is generally
deficient in planted forests because of low annual
precipitation, and this has led to large-scale mortal-
ity of plantations during drought years (22, 23). Since
1949, the overall survival rate of trees planted during
afforestation projects has been only 15% across arid
and semiarid northern China (9). In abandoned ag-
ricultural areas that have undergone afforestation,
most of the precipitation, and in some cases, all of
the precipitation plus some of the soil’s water re-
serve, is consumed by plant transpiration and evap-
oration from the soil surface (24). Previous research
in these regions (25) has revealed that in contrast
with natural grassland and forest, for which water
use was historically in equilibrium with the water
supply, soil moisture content to a depth of 6 m in af-
forestation areas had decreased by 32–37%. A clear
inverse relationship exists between the soil’s water
balance and afforestation of grassland and farmland
(26) because of the large amounts of soil moisture
consumed by fast-growing trees. This moisture can-
not be replenished during the rainy season; thus,
reserves of soil water are depleted, the woody veg-
etation eventually dies because of water stress,
and desertification ensues. Abundant data exist on
the relationship between afforestation in northern
China and decreasing soil moisture (2224), and it
seems reasonable that afforestation with inappro-
priate species will not produce a stable equilibrium
with the available water supply.
China’s implementation of large-scale affores-
tation throughout the country’s arid and semiarid
regions has ignored differences in topography, cli-
mate, and hydrology, all of which can affect tree sur-
vival. For example, wind abrasion of trees has been
a significant problem. Wind speed averages 3–5 m/s
in the Three Norths region and ranges from 4 to 6
m/s during the windy season from March to May; for
20–80 days per year, wind speed exceeds 5 m/s (the
threshold for sand transport). As a result, 10–15% of
newly planted trees were killed by windblown sand
(27). In addition, water availability was insufficient
to support trees in many regions. For example, the
long-term mean precipitation of <200 mm/yr in arid
regions is incapable of sustaining forest vegetation
given the 2500–3000 mm/yr of potential evaporation
common to these areas (28). As a result, natural eco-
systems did not historically support extensive forests
in these regions. The natural vegetation of much of
the region was desert steppe vegetation or dryland
shrub communities, which have a much higher wa-
ter-use efficiency than most tree communities and
which have evolved to use soil water sustainably un-
der these environmental conditions.
To support wood production, which was an eco-
nomic priority, >80% of the afforestation in the Three
Norths region involved monoculture planting; often,
fast-growing species with low water-use efficiency
were used, such as Populus tremula L. (7). These
monocultures typically consumed 20–40% more soil
moisture than the steppe species that the trees re-
placed, leading to drying out of the soils, soil degra-
dation, and greatly increased tree mortality (29). In
addition, the water-stressed trees became increas-
ingly vulnerable to plant diseases and insect pests
(7). In total, 400 million ha of P. tremula monocul-
ture was affected, and 15,000 ha/yr of plantations
has died as a result of infestation by Anoplophora
glabripennis Motsch. and Anoplophora nobilis Gan-
glbauer (two wood-boring beetles) in northern Chi-
na (30).
Adverse impact of afforestation on landscapes
in arid areas
Vegetation cover. The above-mentioned decrease in
soil moisture in afforestation plots, combined with
reduced sunlight under the tree canopies (which ad-
versely affects the growth of understory vegetation),
has led to decreased vegetation cover in the affor-
estation plots. Net decreases of 30.5% occurred by
the seventh year after trees were planted in grass-
land areas in northern China that had undergone
afforestation; sometimes even entirely bare ground
was produced (25). Because dense steppe vegetation
can absorb more of the wind’s momentum than less
F I G U R E 2
Sandstorm frequency in China since
1950
Data from Ref. 4 and Refs. 14–19.
Sandstorm frequency (number/yr)
Decade
1950–
1959
1960–
1969
1970–
1979
1980–
1989
1990–
1999
2000–
2006
11
10
9
8
7
6
5
4
3
2
1
0
1828 EnvironmEntal SciEncE & tEchnology / march 15, 2008
dense plant communities or bare soil, this vegeta-
tion can effectively control wind erosion (31). Regres-
sion analysis indicated that the rate of wind erosion
decreased linearly with increasing plant density,
aboveground biomass, and species richness. The
rate of wind erosion was most strongly affected by
vegetation cover, which accounted for 48.1% of the
variation in erosion (32). These results suggest that
the frequency of windblown sand would increase
abruptly wherever the vegetation cover decreased as
a result of afforestation (33). In addition, part of the
airflow around sparsely forested areas is deflected
downward by the trees and strikes the bare ground,
increasing sand motion when airflow is blocked by
the sparse trees during windy weather. This concen-
trates airf low at ground level (Figure 3), increasing
the wind’s erosive force (27) and generating larger
sandstorms. Significant negative relationships were
also found between the rate of wind erosion and soil
moisture content, because moist soils are more co-
hesive and thus less vulnerable to wind (34).
In the aforementioned study (32), soil moisture
content exerted a strong inf luence on the rate of
wind erosion, accounting for 13% of the variation in
erosion. Last but not least, vegetation cover can sig-
nificantly reduce the magnitude of erosion caused
by surface runoff. Because large drops of water im-
part a significant force on the soil, and vegetation
can slow the arrival of water at the soil surface to a
rate closer to the soil’s ability to absorb the water,
interception of these drops by leaves can greatly re-
duce water-caused erosion. In contrast, with mono-
culture plantations, erosion by water can increase,
particularly in comparison with grassland ecosys-
tems, because of the reduced vegetation cover under
the trees (35). Although certain management prac-
tices used during afforestation, such as trenches cre-
ated parallel to topographic contours to intercept
surface flow (photo on p 1826), can reduce water-
caused erosion, the decreased vegetation cover can
offset this advantage by increasing wind erosion. In
one Chinese study, 70% of desertification was caused
by wind erosion versus only 10% by water erosion
(36). For these reasons, large-scale afforestation in
arid and semiarid China appears to have been un-
able to control desertification and may actually be
exacerbating the problem.
Hydrology. Many previous studies have reported
that when the consumption of precipitation by tree
plantations is higher than the level of consumption
by natural vegetation, increased forest cover reduces
the net runoff from a watershed (21–25). Previous
research in northern China (22) revealed that the
runoff from afforestation plots decreased by an aver-
age of 77% (ranging from 57 to 96%) compared with
grassland and farmland. Although this decreased
runoff suggests increased retention of precipitation
and decreased water erosion, the retained moisture
is often used more rapidly than it can be replenished
during the rainy season. As a result, the trees actu-
ally decreased the belowground water supply and
the supply of water to rivers (25), and any soil conser-
vation achieved by the trees was subsequently off-
set by more severe wind erosion (36). Although the
Chinese government has invested ¥40 billion in the
South-to-North Water Transfer Project, designed to
transfer 11.7 billion m3 of water per year to mitigate
water shortages in northern China (10), large-scale
afforestation appears to be exacerbating the water
shortage in northern China.
The groundwater reserve in any area has accu-
mulated over historical periods and has generally
reached equilibrium with the area’s climate dur-
ing periods of climatic stability. In arid regions, this
water supply can sustain trees initially even when
natural precipitation is inadequate to support for-
est vegetation. This is why many researchers have
reported successful afforestation of large areas of
desert. However, as afforestation expands and more
trees begin growing in an area, the trees gradually
deplete the groundwater to compensate for the in-
adequate precipitation. The effects of this depletion
can be subtle at first, and as a result, people have
been fooled by small-scale and short-term results
into believing that desertification can be solved by
large-scale afforestation. Unfortunately, the effects
of increasing depletion of groundwater often be-
come apparent many years later. For example, dur-
ing the 1970s, the initially successful revegetation
process used to stabilize mobile sands in part of the
Mu Us Sandland served as a model for the rest of
China, but 20 years later, >70% of the trees had died,
and vegetation cover fell to even lower levels than
before the afforestation as renewed desertification
erased the early gains and soil moisture shortages
were exacerbated (37). If policy makers are unwill-
ing to adjust the current strategy, the afforestation
projects not only will affect the present landscape
but also will have adverse impacts on China’s future
environment.
F I G U R E 3
Mechanism responsible for increased
desertification
When an individual tree grows in arid or semiarid
land in the absence of other vegetation to control
sand movement, wind directed downward along the
tree trunk strikes the bare ground and increases the
entrainment of sand par ticles.
Airflow
Sand–airflow
Airflow
ma rch 15, 200 8 / E nvi ro nm En tal Sc iEnc E & tE ch no lo gy 182 9
Implications for practice
Although vegetation restoration is difficult, the cre-
ation of artificial ecosystems (i.e., forest plantations)
that are inappropriate for their environment has
caused the failure of this approach to combat desert-
ification (38). However, desertification has been at-
tributed primarily to human activities (1), especially
to livestock grazing and farming (2, 5), and second-
arily to climatic changes (39). Therefore, we should
certainly influence human activities, and doing so
will be one key to reversing desertification: every
ecosystem has a finite carrying capacity, and when
that capacity is exceeded, degradation of the ecosys-
tem occurs (40). However, ecosystems that are not
damaged too badly show a remarkable ability to re-
store themselves rapidly and economically through
natural processes (41), and this suggests that the key
strategy to combat desertification will be to better
understand the natural carrying capacity of each
ecosystem and to use the ecosystem’s resources sus-
tainably to avoid damaging the ecosystem beyond
its ability to self-repair.
In terms of revegetation strategies, planners must
understand that different environments will support
different vegetation communities and that forests
are not a suitable choice in all areas. To success-
fully revegetate an area, planners must determine
which vegetation types a given environment can
naturally sustain and target restoration activities
at creating such communities. For example, stable
communities of natural desert steppe and grass-
land vegetation, and possibly even lichen species
in more severely degraded environments, can de-
velop in arid and semiarid areas as a result of natu-
ral processes, thereby increasing vegetation cover
beyond the levels that could be sustained for trees,
and can thereby provide better protection for the
soil. The resulting communities exhibit decreased
consumption of soil moisture, improved resistance
to diseases and insect pests, and thus a greater abil-
ity to restore a stable ecosystem (42).
The observations above suggest that it would be
more effective for the Chinese government to reduce
its investment in afforestation and spend more on
other proven strategies for controlling desertifica-
tion. For example, the government should encourage
the abandonment of farming in fragile and damaged
areas and the removal of livestock from overgrazed
areas, because such strategies have had large posi-
tive effects on vegetation cover, at less cost (43). To
control desertification, China’s government should
also enlarge the Natural Forest Conservation Pro-
gram (6), with the aim of banning further logging of
natural forests and grazing in arid areas. Afforesta-
tion in arid and semiarid regions should be limited
to the most mesic areas (25), with species such as
dwarf shrubs chosen on the basis of maximum wa-
ter-use efficiency rather than economic goals, such
as the rapid production of wood fiber.
Shixiong Cao is a postdoctoral fellow in the College of
Economics and Management at the China Agricultural
University in Beijing. Address correspondence about this
article to Cao at shixiongcao@126.com.
Acknowledgment
I thank Geoffrey Hart for his help in writing this art icle.
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ma rch 15, 200 8 / E nvi ro nm En tal Sc iEnc E & tE ch no lo gy 183 1
... However, it remains controversial on the relative contribution of the policies driving recovery efforts to vegetation restoration. For example, it is reported that ecological projects had failed to reverse desertification in northern China during the early stage of afforestation [35]. A study also illustrated that the effect of human activities on vegetation greening was far less than climate at a regional scale on the Mongolian Plateau [36]. ...
... As we summarized in Figure 13, during the last four decades, the government has implemented a lot of ecological conservation policies and projects, such as the TNSFP, the GGP, and NFPP. Although some policies were proposed before the 2000s, such as the TNSFP, which began in 1978 and has been the largest afforestation project in the world, was less effective than expected in some eco-fragile regions [35]. Our study also confirmed that the unfavorable environment could not be improved effectively by these early ecosystem restoration programs due to many factors, such as lower temperature, drier conditions, and atmospheric CO 2 concentrations, compared to that in the new century. ...
... Afforestation is difficult in these eco-fragile environments when ignoring natural ecosystem characteristics in dryland regions. A study showed that the overall tree survival rate during the afforestation project of TNSFP from 1949 to the early 2000s was only 15% in the drylands of China [35] and was not effectively implemented to promote vegetation deforestation in the early stage of the project. Therefore, the ecological policies had limited effects on vegetation restoration in the stage before 2001. ...
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Climate change and human activities significantly affected environmental changes in drylands. However, the relative roles remain unclear regarding these factors’ effects on environment changes in drylands. Herein, we analyzed vegetation change trends using remote-sensing datasets to determine the interactions of vegetation, climate, and anthropogenic activities in an arid region of China, Kubuqi Desert. Our study showed that 67.64% of the pixels of fractional vegetation coverage (FVC) increased in 2020 in comparison with those of 1986. The FVC exhibited a significant greening trend (0.0011/yr, p < 0.05) in 1986–2020 as a whole. This greening trend revealed two distinct periods separated by a turning point in 2001. There was no clear trend of FVC before 2001, and then there was a dramatically greening trend since 2001 in most regions of the study area. The increasing rate (0.0036/yr) in the later period was three times higher than the entire period. The accelerated increasing trend was due to the variable compound effects of climate and human activities. The correlation between FVC and precipitation was mainly positive, which outweighs the significantly negative correlation between vegetation and temperature. However, both climatic factors cannot well explain the trends of vegetation dynamics, implying a possible role for human activities. Generally, climate change and anthropogenic activities contributed 42.15% and 57.85% to the overall vegetation variations in 1986–2020. Specifically, the relative role of the two factors was vastly different in two distinct periods. Climate change led the dominant roles (58.68%) in the vegetation variations in 1986–2001, while anthropogenic activities dominated (86.79%) in driving vegetation recovery in the period after 2001. Due to the massive ecological conservation programs such as the Grain for Green Project launched in 2001, substantial deserts have been transformed into grasslands and forests. This analysis highlights the ecological policies largely responsible for vegetation restoration and provides references for ecological protection and sustainable development in eco-fragile ecosystems.
... The potential for China's large-scale natural restoration efforts to resolve environmental problems in some areas has engendered much scientific debate Wu et al., 2013). As noted by Cao (2008), extensive afforestation efforts in arid and semiarid regions steeply increased regional evapotranspiration , depleting limited soil water (Deng et al., 2016), and eventually exacerbating desertification (Cao, 2008). According to a quantitative assessment, tree planting has been proved to be ecologically unsustainable in areas where the annual precipitation averages less than 400 mm (Tian et al., 2017). ...
... The potential for China's large-scale natural restoration efforts to resolve environmental problems in some areas has engendered much scientific debate Wu et al., 2013). As noted by Cao (2008), extensive afforestation efforts in arid and semiarid regions steeply increased regional evapotranspiration , depleting limited soil water (Deng et al., 2016), and eventually exacerbating desertification (Cao, 2008). According to a quantitative assessment, tree planting has been proved to be ecologically unsustainable in areas where the annual precipitation averages less than 400 mm (Tian et al., 2017). ...
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China has long suffered from failures in urban governance, arable land conservation, and environmental conservation because of the lack of accurate and reliable land use data. To fill these gaps, China has been conducting a once-a-decade census of national land use status. On August 26, 2021, China released the third national land survey data, which revealed several challenges that require further attention. In this paper, we first review the land resource surveys that have been and are being conducted in the world's major economically developed countries, and then we compare China's three national land surveys in terms of the data used, core survey technologies, the land use classification system, and main outcomes. Second, according to the major data results of the second national land survey and the third national land survey and other auxiliary data, using such methods as the data envelopment analysis and the land cover conversion matrix to highlight the existing land use issues such as shrinking arable land, inefficient construction land use, and low targeting efficiency of ecological restoration programs, as well as the drivers of these issues. Finally, we conclude the paper by discussing the next steps necessary to achieve the goal of sustainable land use in China, and the potential of satellite remote sensing technology and its derived land cover products to better support future national land surveys.
... However, its use in the dendrogeomorphology of landslides is (to our knowledge) still absent. At the same time, it is a species that is widespread in landslide areas because it can drain and mechanically stabilize landslides (Cao, 2008;Wu et al., 2015). R. pseudoacacia is generally a ring porous tree (although it can also be semiporous). ...
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... in drylands can have low success rates when implemented without consideration for varying topography, climate, and hydrology when planting vegetation in an ecosystem. For example,Cao et al. (2008) found that large-scale reforestation efforts in semiarid and arid regions of China since 1949 have only had a 15% success rate. For economic reasons, such as supporting wood production, monocultures of fast-growing species which weren't suited to the environment were planted as opposed to desert steppe vegetation or dryland shrubs. ...
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Somaliland is prone to weather disasters, primarily droughts which are increasing in frequency and intensity due to the climate crisis. Ecosystem-based Disaster Risk Reduction (Eco-DRR) offers a community-led approach to increasing resilience in the face of these crises, through building robust ecosystems that shield vulnerable populations from the effects of climate change. This concept is very new to Somaliland and there is currently no literature addressing strategies for implementing Eco-DRR based on geospatial variation in climate change vulnerability and conditions. This study uses climate vulnerability mapping (CVM) to quantify the vulnerability exhibited by different regions and areas throughout Somaliland, identifying the spatial variance in severity of vulnerability components (exposure, sensitivity and adaptive capacity). The knowledge extracted from CVM is then combined with knowledge gathered in a literature review on climate change and environmental conditions in Somaliland to make recommendations for Eco-DRR opportunities in the state. This study found that there is wide scope for the utilisation of Eco-DRR in Somaliland through measures such as sustainable land management (SLM), rainwater harvesting and reforestation. CVM revealed that 88.07% of land in Somaliland is of medium vulnerability or higher to climate change, highlighting the susceptibility of the semi-arid to arid climate to disasters and the state's limited capacity for resilience. The ongoing drought in Somaliland is devastating dryland communities; internal displacement and famine in dryland communities will need to be addressed before paving the way for Eco-DRR administration to mitigate the impacts of future disasters. 3 Declaration of Originality I have read and understood the University's policy on plagiarism.
... Taking the Bashang Plateau of Zhangjiakou City as an example, the total water supply of water conservancy projects in this area was 222.2902 million/m 2 in 2011, of which the agricultural water consumption was 186.9864 million/m 2 , accounting for 84.12% of the total water supply in the whole region, and the water consumption of vegetables accounted for 89% of the agricultural water consumption [14]. Besides, in order to prevent and control vegetation degradation and soil wind erosion and desertification in Bashang Plateau, afforestation activities have been carried out in the large area since 1979, and transpiration of forest land also consumes a lot of water resources in the area [16] [17]. ...
... China has implemented a wide range of national policies for ecological protection, including policies on afforestation, returning cultivated land to forest and grassland, forbidding grazing, zoning, ecological migration, which has improved land-use structure and the growth conditions of grassland vegetation, increased vegetation cover, total NPP, soil conservation, and water yield, and reduced soil erosion [34,[58][59][60]. All these play important roles in nature conservation and restoring China's degraded ecosystems, especially in western China [61,62]. Over the past decade, the ESV in the study area has shown a trend of growth. ...
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Policies directly affect land-use change, which in turn, affects ecosystem services. In parallel with the implementation of a full-scale development program for the western region, the Chinese government has introduced a series of ecological protection and restoration strategies for development and construction. This study conducted a quantitative spatial evaluation of the ecosystem service value (ESV) of national nature reserves in the western region under this dual policy of development and protection. On the basis of land-use data and related evaluation parameters, fluctuations in the valuation of ecosystem services during 2000–2010 were analyzed in response to land-use changes under the comprehensive policy. Results showed that the increases in the areas of forestland and water bodies led to an increase of CNY 74.1 billion in the ESV from 2000 to 2010, equivalent to 2.02%. Grassland with increased production capacity and water bodies were the main factors driving the total ESV dynamics. Values of all ES increased significantly. Therefore, the ecological conservation and restoration policy, along with the development policy, had a positive influence on ecosystem services in the nature reserves in western China.
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Ecological regions of medium fragility account for 55 % of China's land. Large-scale afforestation and land reclamation have been carried out in these areas over the past few decades. However, how future climate change poses risks and challenges to them remains unclear. By establishing a multi-algorithm framework combining machine learning algorithms with multi-source dataset, our work predicts Normalized Difference Vegetation Index (NDVI, a proxy for vegetation greenness) and its variations in the 21st century under different climate scenarios. We find that vegetation greening (i.e., NDVI increase) in northern and southwestern China is unstable over four 20-year periods from 2020 to 2100. However, a strikingly prominent greening is expected to occur on the Qinghai-Tibet Plateau until the end of this century. Future warming can not only exacerbate the difficulties of vegetation conservation and restoration in vulnerable ecological regions, also threaten these new croplands, stymieing ambitions to increase crop production in China. Our results underscore the crucible that a warming climate presents to current restoration projects. We highlight the urgency of adapting to climate change to achieve ambitious goals of carbon sequestration and food security in China.
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The "Three North Shelterbelt Development Program" and a variety of greening programs in China have been undertaken since the late 1970s, resulting in the world´s largest forestation and renaturation area over 4,800 km of sub-humid to hyper-arid climate zones across Northern China. The large-scale afforestation activities were done mainly to reduce consequences from desertification in the north, i.e. large dust storm events called "Yellow Dragon" that affected the entire country. Some planting campaigns have used non-adapted or not native tree species, leading to hydrological and/or ecological stress and subsequent tree mortality. The recent trend of worsening in some climate parameters in Northern China has further reduced billions of planted trees' viability. We present results from example regions and review the overall efficacy of this unique long-term desertification control program. How can we restore degraded regions to achieve acceptable survival rates and adaptability of the new vegetation to climate change? Some factors that have been identified as key in the success of restoration of degraded land in Northern China will be presented, focusing on the recent concept of "natural renaturation" that was started here basically in 2006. It uses the process of natural succession, a method that relies on the self-restoration capacity of undisturbed nature to develop new vegetation over time, often many years. This method so far has only started being applied to drylands. Fifteen years after its implementation, we find encouraging results as to increases in biomass. The long-term assessment of vegetation developed in natural succession is expected to indicate superiority in ecological parameters and viability. Will this method become a successful and important component in the fight against desertification?
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Afforestation has been initiated in Northeast Asia to improve ecological status. The responses of the regional hydrological cycle to vegetation restoration remain insufficiently explored. This study uses a variety of satellite-derived vegetation variables and hydrological cycle components to scan the eco-hydrological regimes in the Three-North Region of China and Mongolia during the past four decades. We observe that vegetation productivity increases mainly in North China (NC), Northeast China (NEC), Northwest China (NWC), and the north of Inner Mongolia and Mongolia. Precipitation and runoff show a decreasing trend (-0.4 mm/year and - 0.6 mm/year, respectively), yet they are less correlated to the normalized difference vegetation index and leaf area index. Along with increasing vegetation productivity, evapotranspiration increases (0.05 mm/year) obviously in NC and NEC, while root soil moisture (-0.001 m3/m3/year) and terrestrial water storage (-2.0 mm/year) decrease in NC and parts of NEC and NWC. The correlation coefficient between evapotranspiration and vegetation variables is up to 0.73. Collectively, results imply one potential adverse response of terrestrial water fluxes to increasing vegetation. Independent ecological and hydrological datasets further corroborate our work. Climatic factors (i.e., downward shortwave radiation and air temperature) and human activities (i.e., aerosol optical depth, carbon dioxide, and water withdrawal) substantially affect regional hydrological cycles. Considering the increasing vegetation productivity in the Three-North Region of China and Mongolia is likely to continue in the 21st century based on the Sixth Coupled Model Intercomparison Project (CMIP6) simulations, the terrestrial water fluxes may undergo deficit pressure. Overall, this study comprehensively investigates the vegetation and hydrology interplays, and provides a reference for protecting and improving ecological-hydrological conditions in Northeast Asia.
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Forests provide vital ecosystem services such as soil and water conservation, climate regulation, and carbon storage. Large-scale afforestation programs are being attempted in many countries to improve environmental conditions in deteriorated or unfavorable locations. China's Three Northern Protected Forest Program (TNSFP), accounting for 42.40 % of China's total land area, is the world's largest afforestation program to date. The TNSFP has continued providing critical ecosystem services to humans over 73 years (1978-2050) with a total investment of CNY 93.3 billion. To facilitate understanding of the TNSFP's contribution, the effects of the TNSFP for last 43 years were comprehensively evaluated by using integrated review of structured literature, bibliometric analysis, and thematic analysis. We incorporated and expanded the direct ecosystem services evidence of the TNSFP from wind and sand control, soil erosion control and carbon sequestration to indirect economic benefits, e.g. increasing crop yield and promoting economic development. We found that over the past 40 years of TNSFP construction, wind and sand hazards and soil erosion in China's Three-North areas have been effectively controlled, and forest carbon sequestration, grain production and economic output have steadily increased. The ecosystem services provided by the TNSFP are highly consistent with the thrust of the UN Sustainable Development Goals, and the TNSFP has contributed to the realization of SDG2, SDG8, SDG13, and SDG15. Although achieving tremendous ecological, economic, and social benefits, the TNSFP still has knowledge gaps in its scientific basis. And the limited local engagement and insufficient investment highly hinder the TNSFP from playing its multiple functions. We suggest several urgent actions and directions to address these limitations. This review could help researchers gain insight into key areas of ecological restoration in the TNSFP, providing a reference for future research in the TNSFP construction in China and other regions of the world embarking on similar journeys.
Conference Paper
Arid and semi-arid regions occupy nearly half the area of China, where there are abundant natural resources and a great potential for development. However, these regions have been seriously troubled by sandy desertification which has become an important restricting factor for local development. On the basis of research and practice over many years, we believe that sandy desertification is environmental degradation indicated by wind erosion resulting from excessive human activities. The degraded land is desertified land. Between the important human and natural contributing factors, the former is the more crucial. The evolution of sandy desertification depends on the process of wind erosion after the ecosystem has been destroyed by humans, and its indicator is mainly presented by wind-erosion landforms. Sandy desertification leads to a rapid decline in the biomass production and the potential productivity of land, and even loss of land resources. The trend of sandy desertification will depend fundamentally on the human impact in coming decades. A number of typical examples have proved that the desertified land can be restored to its potential productivity for agriculture and animal husbandry through different harnessing measures.
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The definition of desertification accepted in the ad hoc conference held by UNEP in Nairobi in 1977 and confirmed at the Earth Summit on Environment and Development held in Rio de Janeiro in 1992 is: ‘arid, semi-arid and dry-subhumid land degradation’. There is no global long-term trend in any rainfall change over the period of instrumental record (c. 150 years), but there has been an increase of 0·5°C in global temperature over the past 100 years. This increase seems partly due to urbanization, as there is no evidence of it resulting from atmospheric pollution by CO2and other warming gases (SO2, NO2, CH4, CFH etc.). On the other hand, the thermal increase is uneven, increasing with latitudes above 40° N and S. The increase is only slight or non-existent in subtropical and inter-tropical latitudes where most arid and semi-arid lands lie. This, incidently, is consistent with Global Circulation Models (GCM) — derived scenarios. The study of tree-rings, lake level fluctuations and pollen analysis confirm the existence of climatic fluctuations, but with no long-term trends over the past 2000 years.
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The dry and cold Tibetan Plateau is, by its nature, sensitive to desertification, and now human impacts and overexploitation makes things worse. One of the most important things involved in combating desertification is to stabilize mobile sandy land and facilitate revegetation. A study was conducted on shifting sand dunes of Tibetan Plateau to investigate the relationships among sand control, vegetation restoration and diversity dynamics of seed plant species. It was found that a positive correlation lay between sand stabilizing shrubs (Caragana korshinskii and Artemisia ordosica) and Leymus secalinus, a species of dominant and perennial grass in well-restored vegetation, but a negative correlation occurred between those shrubs and Agriophyllum arenarium indicator of shifting dunes. Secondly, sand stabilization facilitated revegetation, and total cover and cover of L. secalinus rose continuously from the beginning of restoration, but diversity indices showed a complex tendency. Based on these results, it was reasoned that on alpine shifting dunes of desertified regions, continual sand drifting caused by gales was the limiting factor for plant to survival. If sand barriers were established, sand drifting would be effectively controlled, then many native plant species could colonize shifting dunes gradually, so the process of revegetation was facilitated.
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The definition of desertification and its causes in the Chinese literature are reviewed and compared with those in international publications. Both Chinese researchers and their western counterparts have difficulty in reaching a generally accepted definition for desertification and an agreement upon the exact role played by human activities and environmental settings in desertification initiation and development. Tremendous efforts in China have gone into rehabilitating desertified land into productive uses with great contribution to existing knowledge in reclaiming desertified land. The early biological-oriented measures based solely on economic return have recently been replaced by a much more successful, multi-disciplinary approach of rehabilitation combined with preventive measures that follow sound ecological principles.
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In an effort to halt soil erosion, desertification and sandstorms, the Chinese government has recently launched a series of land conservation programs targeted at the country’s north, northwest and southwest areas where problems are severe. This paper provides an overview of the current status of the major land conservation projects and their environmental and social-economic significance, as well as the challenges encountered. Conflicts of interests and objectives among different administrative entities involved and problems associated with the lack of local participation are addressed. Impacts on the food economy and implications for the environment are discussed in light of the options for meeting the country’s increasing food demand. The analysis highlights the necessity of improving cooperation and integration across different administrations and the imperative of participation of local communities in the planning and management process for achieving the goals of land conservation campaign. The importance of internalizing the environmental externality of land degradation and stipulating sustainable national food supply strategies is also stressed.
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Microscopic examination of microbiotic soil crust shows that the profiles of soil with a dense cyanobacterial cover had two different layers: a surface thin layer composed of aeolian-born materials and an organic layer formed by filamentous cyanobacteria associated with sand particles. The results indicate that microbiotic cover is an important determinant of sand fixation in the Gurbantunggut Desert, northern part of Xinjiang, Northwestern China. Microscopic examination of microbiotic crusts in this study revealed an intricate network of filamentous cyanobacteria and exopolysaccharides, which binds and entraps sand grains and conglutinate fine particles with each other. Resistance to wind erosion paralleled the different disturbance levels on microbiotic soil crust. Sandy soil surface disturbances resulted in greatly decreased soil resistance to wind erosion. Maximum wind tunnel velocity in this test (25 m s−1) did not lead to any wind erosion on the surface of undisturbed microbiotic soil crust, i.e. 100% covered by microbiotic soil crust. As for different disturbance levels, the highest threshold friction velocity was seen in the sand surface with 10% disturbance of microbiotic crust. The surface microbiotic soil crusts have great effects on wind erosion rates. Wind erosion rates for sandy soil with 0% crust cover was about 46, 21, 17 times the soil with 90% crust cover at wind velocities of 18, 22, 25 m s−1, respectively.This study confirms that the planners and managers of nature reserves in this area should understand the important ecological roles of microbiotic crust in desert ecosystems. The reduction of trampling on the soil will eventually result in the re-establishment of biological crusts and their associated organisms, and ultimately lead to lower levels of wind erosion. Additionally, strategies should be developed to manage livestock and oil exploration in order to avoid concentrated zones of impact.
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A half-century policy of forest exploitation and monoculture in China has led to disastrous consequences, including degradation of forests and landscapes, loss of biodiversity, unacceptable levels of soil erosion, and catastrophic flooding. A new forest policy had been adopted in China called the Natural Forest conservation Program (NFCP), which emphasizes expansion of natural forests and increasing the productivity of forest plantations. Through locally focused management strategies, biodiversity and forest resources will be sustained, and downstream regions will be better protected from flooding. This new policy is being implemented with a new combination of policy tools, including technical training and education, land management planning, mandatory conversion of marginal farmlands to forest, resettlement and retaining of forest dwellers, share in private ownership, and expanded research. These policy tools may have wider relevance for other countries, particularly developing countries.
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Loessial sandy loam soils are the major soil categories in the northern Loess Plateau, China. Owing to a dry, windy climate and sparse surface cover, wind erosion is a serious problem and dust (sand) storms occur frequently. Soil moisture is one of the most important factors influencing resistance to wind erosion. The influence of moisture content on the erodibility of sandy loam soils was investigated through wind tunnel simulations. Results showed that the threshold velocity for soil particle movement by wind increases with increasing soil moisture by a power function. The intrinsic factor in the increase in soil resistance due to moisture content is the cohesive force of soil water. Cohesive forces of the film and capillary water are different; the influence of soil moisture on threshold velocity was shown to follow a step-like pattern. The wind erosion modulus of sandy loam was directly proportional to the cube of the wind velocity or the square of the effective wind velocity (V−Vt). There existed a negative exponential relationship between the wind erosion rate and soil moisture content. Initially, as soil moisture increased the decrease in the wind erosion rate was rather rapid. When the moisture content reached more than 4%, the rate of decrease in erosion slowed and became almost constant with successive increments of moisture. This suggests that different soil moisture contents can prevent wind erosion at different levels. Four percent soil moisture could only reduce the erodibility of the sandy loam soil by a small degree.