Desertification Change Research Articles

The response of soil CO2 efflux to desertification on alpine meadow in the Qinghai–Tibet Plateau

Assessing the global C budget requires a better understanding of the effect of environmental factors on soil CO2 efflux from both experiments and theoretical research, especially in different desertified lands in the Qinghai–Tibet Plateau. Based on the enclosed chamber method, soil CO2 efflux in four different desertified lands and one control [alpine meadow (AM)] were measured in June, August and September, 2008, respectively. Soil CO2 efflux rates at the top, the middle, the bottom of a slope and the flat in front of the slope were obtained at Maduo County. The results showed that average daily soil CO2 efflux rates were 3.72, 2.65, 2.68, 0.59 and 0.37 g m−2 day−1 in the AM, lightly (LDL), moderately (MDL), severely (SDL) and very severely desertified lands (VSDL) during the growing season, respectively. Soil CO2 efflux decreased with the change of desertification. The response of soil CO2 efflux to environmental factors was adequately described by the linear model; models accounted for 76, 65, 72, 59 and 71% of the variability on soil CO2 efflux in the AM, LDL, MDL, SDL and VSDL, respectively. Any environmental factor, however, was insufficient to explain the soil CO2 efflux; the common influence could perfectly reflect soil CO2 efflux response to the desertification change.

Climate, Desertification, and the Rise and Collapse of China’s Historical Dynasties

IntroductionArid and semiarid areas of ancient China include theMongolian Plateau, northern China, and some parts ofcentral China. These regions have experienced multiple aridphases throughout the Quaternary, and are highly sensitiveto climate change (Z. Zhu and Liu 1982). These areas weretraditionally managed using fragile pastoral and agriculturalsystems even though most of this area is covered by gobideserts, eolian dunes, sandy land, and steppes (Fig. 1),where both agriculture and the native vegetation have beenseriously degraded by frequent desertification cycles (Z.Zhu et al. 1980). Over the past 5,000 years, Chinesedynasties have been founded, have flourished, and have thendeclined and collapsed in various regions. In particular, therise and decline of dynasties in northern and central China,possibly due to desertification cycles, strongly influencedChina’s historical cultures (Rhoads 2003), which themselvesplayed a dominant role in Asian and world history(Stavrianos 1999). The Mongolian Plateau and northernand central China, where historical dynasties were supportedby traditional pastoral and agricultural systems, were highlysensitive to changes in desertification and biological produc-tivity produced by the late-Holocene Asian Monsoon (Neffet al. 2001;Fleitmannet al. 2003). Because of theimportance of a stable food supply to support the largepopulations required to economically and militarily sustain adynasty, these changes would have had a direct impact onthe health of dynasties in these regions.Archaeological evidence (Bao and Zhang 1984;FengandJiang 1996) reveals that cycles of desertification anddecreasing biological productivity occurred frequentlyand in almost all cases, dynasties flourished when desertifi-cation was reversing and biological productivity wasincreasing, and collapsed when desertification expanded intheir core regions (H. Wang 1996). Similarly, Man et al.(2000) suggested that the climate changes during historicalperiods had significant effects on changes in the position ofagriculture–grazing transitional zones and the fate of Chinesedynasties. However, the rise and decline of China’shistoricaldynasties and their relationship to changes in the region’sclimate are poorly understood. While there is considerableevidence for the effects of cultural and other socioeconomicfactors (Lv 1991), and there is some evidence of the collapseof dynasties during periods with a weak summer AsianMonsoon (Yancheva et al. 2007) or periods with unusuallylow temperatures (Zhang et al. 2007), the overall influenceof climate remains poorly understood.However, recent advances in climate change researchusing proxies allow a review of the relationship betweenclimate and the fate of the dynasties using high-resolutiondata. We here present evidence from published high-

Climate change and desertification in South Africa—science and response

Despite significant attention paid to desertification and climate change in the last few decades, interactions between the phenomena, as well as implications thereof, have received less of a focus. Such a trend is particularly marked in the science– policy arena, at multiple scales. Reynolds et al. (2007) observe, for example, the lack of a focused international science programme in desertification—a gap that may compound the problem. This article seeks to unpack two-way interactions between climate change and desertification, using selected case studies from the South and southern African, and global, contexts. It considers emerging approaches to responding to climate change in the context of desertification, emphasising the need for improved integrated biophysical and social science approaches, a focus on multiple synergies and cross-sectoral strategies, and the need for improved communication across the science–policy divide.

Assessing the relative role of climate change and human activities in sandy desertification of Ordos region, China

Climate change and human activities are driving forces of sandy desertification and the relative role of them in sandy desertification is the hot point in related researches. A study was carried to assess the relative role of climate change and human activities in sandy desertification of Ordos region in China. Potential NPP and the difference between potential and actual NPP were selected as indicators to assess the relative role of climate change and human activities in sandy desertification, respectively. Assessing methods were built based on some scenarios for the reversion and expansion of sandy desertification and the relative role of climate change and human activities in sandy desertification of Ordos region were assessed from 1981 to 2000. The results showed that although some local places experienced an expansion of sandy desertification, the change of sandy desertification of Ordos region from 1981 to 2000 showed a stably reversing trend. The relative role of climate change and human activities in sandy desertification of Ordos region varied at different temporal and spatial scales in the reversion and expansion processes. In the reversion of sandy desertification, climate change was the dominant factor in the period of 1981 to 1990 and the reversed areas mainly induced by climate change including Mu Us sandy land and the transition zone between temperate steppe and temperate deciduous scrubs in north east of Ordos region; however, human activities controlled the reversed process during the period from 1991 to 2000 and the areas mainly induced by human activities distributed in all banners of Ordos region. In the expansion of sandy desertification, human activities were the dominant factor in the period of 1981 to 1990 and the expanded areas mainly included the regions around common boundary of Hanggin, Dalad Banners and Dongsheng City; however, climate change dominated the expansion of sandy desertification from 1991 to 2000, the expanded areas equably distributed in the whole of Ordos region except the south east of Otog Qian, Uxin and Jungar Banners.

Desertification in China: An assessment

Arid and semiarid China have experienced multiple arid phases throughout the Quaternary, and over the past five decades, there have been several periods with relatively high or low rates of desertification and rehabilitation. The causes of these changes and their historical trends have been debated by scientists because of their potentially huge significance for China, as well as for the global ecology and food supply. This paper reviews recent studies of desertification in different regions of arid and semiarid China. In general, the results of systematic monitoring, and analyses of the causes of desertification and the contemporaneous human impacts, suggest that desertification in China has been primarily caused by climate change, and particularly by strong wind regimes (with high sand transport potential) accompanied by decreased spring precipitation. Unfortunately, although numerous scientists have claimed that desertification in China is primarily due to human impacts; there is surprisingly little unassailable evidence to support this claim. The review presented in this paper show that desertification in China is likely to be controlled by climate change and geomorphological processes, even though human impacts have undeniably exacerbated their effects. Our arguments for both climate change and human activity as factors responsible for the observed changes in desertification rely primarily on inferences based on correlations between trends, thus future research must seek stronger and more direct evidence for the causal relationships that we have proposed as possibilities. This improved information is essential to provide a firm basis for future policy decisions on how best to combat desertification.

Sandy desertification change and its driving forces in western Jilin Province, North China

This paper investigates the sandy desertification change between 1986 and 2000 in the western Jilin province, North China. Land use and land cover data were obtained from Landsat TM data by using a supervised classification approach. We summarized the total area of desertified land by each county, as well as the area for each of the four categories of desertified land. The changes of different types of land use and land cover between 1986 and 2000 were calculated and analyzed. Taking Tongyu and Qianan as examples, both human and natural driving forces of the sandy desertification were analyzed. Our analyses indicate that the material sources and windy, warm and dry climate are the immanent causes of potential land desertification, while the irrational human activities, such as deforestation, reclaiming and grazing in the grassland, are the external causes of potential land desertification. However, rational human activities, such as planting trees and restoring grassland can reverse the land desertification process. Furthermore, the countermeasures and suggestions for the sustainable development in ecotone between agriculture and animal husbandry in North China are put forward.

William R. Barclay, MD, 1919-2006

it seems likely that the meningitis belt will spread,” Thomson said. Current efforts to manage meningitis outbreaks in this region focus on vaccinating the population after one has been identified, although often it is too late to prevent an epidemic, Thomson said. But more information about the temporal and geographic distribution of outbreaks, as well as better modeling of the disease’s life cycle, may one day help scientists to develop an early warning system that would allow more timely vaccination efforts. Thomson noted that while infectious diseases are often the focus of efforts to determine how desertification and other environmental changes affect human health, it is important to take a broader view and consider factors that may indirectly affect health. If the environment is degraded, individuals may not be able to grow food, feed their livestock, or have access to clean water. Individuals living in poverty may be malnourished and thus more vulnerable to disease, and are likely unable to afford preventive measures for themselves or their families. “Poverty is really key to the way environmental changes impact on health,” Thomson said.

Agricultural causes of desertification risk in Minqin, China

This study uses statistical modeling techniques to develop a desertification risk index (RI) for Minqin County, Gansu Province, China. Twenty socio-economic factors were selected and compared with the RI results to explore the spatial and temporal variability of desertification risk in the study area and to identify possible local driving forces behind desertification risk. The explanatory factors were different in 1988, 1992 and 1997, possibly reflecting the role of temporal variation as a contributor to desertification. The average number of sheep per-household was found to be an important indicator of change in desertification risk, while changes in ridge crop planting area explained the distribution of the rate of change in desertification risk in 1988–1992. The results suggests that the RI was useful in expanding the understanding of spatial temporal desertification issues in Minqin County, as well as identifying a current set of agricultural activities related to desertification risk. Further, given the limited nature of consistent data and observations for the area, development of the RI also served to establish a baseline for future investigations into desertification change and the risks such change might pose for the region.

Modeling Desertification Change in Minqin County, China

Monitoring environmental processes is becoming increasingly important wherever there is increasing population and economic development pressure placed on fragile environments. Remote sensing, digital image processing, and spatial analysis have proven to be useful technologies in both assessing and monitoring environmental change. In this study, they were used to assess desertification processes and change in Minqin County, China from 1988 to 1997. The results suggest that wind erosion was the dominant cause of desertification in more than half of the study area. Coupled with this were increases in salinization processes, affecting 33.62% of the land area in 1997. Overall, moderate desertification was found to be the dominant desertification grade (43.64% of total area), followed by extreme/severe desertification (26.15% of total area) in 1997. In addition, examination of landscape pattern changes indicated that desertification processes at the landscape level were becoming evident at increasing levels of fragmentation, complexity in shape, and isolation of patches. Major fluctuations in desertification type and grade were found at the fringes of oases, where an ongoing shift was taking place between cultivation, abandonment, and reclamation.

Desertification assessment in China: An overview

Desertification, land degradation in arid, semi-arid, and dry sub-humid regions, is a global environmental problem. Accurate assessment of the status, change, and trend of desertification will be instrumental in developing global actions to prevent and eradicate the problem. As one of the most seriously affected countries, China has made great efforts to combat desertification. Although improvements have been made in some areas, degradation continues to expand and intensify throughout the entire country. Further land degradation assessments, such as assessments made by the Chinese Committee for Implementing UN Convention to Combat Desertification (CCICCD), will be necessary to ensure successful decision-making, to combat increasing desertification, and to implement Western strategies. This paper overviews the state-of-the-art desertification assessments on both the national and local levels. Also, two major problems facing the assessment of degradation—the uncertainty of baseline assessments and indictor systems and the misuse of remotely sensed data sources—are presented along with suggestions for possible solutions to these problems.

Detection of process‐related changes in plant patterns at extended spatial scales during early dryland desertification

AbstractArid and semiarid shrublands occupy extensive land areas over the world, are susceptible to desertification by anthropic use and can contribute to regional climate change. These prompt the interest to monitor and evaluate these lands adequately in order to detect early stages of degradation. Evaluation topics must refer to biology‐relevant characteristics of these systems, while simultaneously satisfying sampling consistency over extended landscape areas. We present an analysis of process‐relevant parameters related to changes in the spatial arrangement of the plant canopy of shrublands inferred from high‐resolution panchromatic aerial photos and Interferometric Synthetic Aperture Radar imagery. We obtained low‐altitude images systematically located along several gradients of land‐use intensity in a Patagonian Monte shrubland in Argentina. Images were digitized to spatial resolutions ranging from 0.09 to 0.72 m (pixel size) and the average values and an‐isotropic characteristics of the plant canopy patterns were quantified by means of a Fourier metric. We used radar‐derived imagery to overlay the panchromatic images on a digital elevation model in order to study the correspondence of potential runoff patterns and the spatial arrangement of plants. We related an‐isotropic features of the plant canopy images to the prevailing wind regime. Observed trends were further interpreted on the basis of a spatial‐explicit simulation model describing the dynamics of the main functional groups in the plant community. We conclude that early stages of anthropic‐driven dryland degradation in the Patagonian Monte can be characterized by the incipient un‐coupling of spatial vegetation patterns from those of runoff at a landscape scale, and a progressive coupling to the spatial pattern of the wind regime. The method and metrics we present can be used to quantify early desertification changes in other similar drylands at extended spatial scales.

Spatial distribution of sandy desertification change in the west of Jilin Province

The sandy land of the western part of Jilin Province is located in the ecotone of semi-humid and semi-arid area in the temperate zone of China. The sandy desertification has widely spread in the region because of the vulnerable natural conditions and the unreasonable human activity; as a result of this, the precious land resources and the economic development in the area have been seriously impacted. In this paper, the sandy land ecologic environment geographic information system is established based on the multi-spectral, multi-temporal Landsat TM images and field investigation. The comprehensive indexes of sandy desertification extent assessment which include vegetation degradation, wind erosion extent and soil depth are presented to classify the sandy land in western Jilin into three levels-slight, moderate and severe sandy desertification with the support of GIS platform. The results demonstrate that the sandy desertification has been partly controlled in the past twenty years, except some small sites. However, this doesn’t necessarily mean that there is nothing for more concern. The two main causes of sandy desertification have not been eliminated yet, one is its natural factor, especially the physical and chemical characters of sandy soil and dry climate; another is the immoderate economic activity of human being that has highly accelerated the sandy desertification process.

Drought, desertification, and climate change

Drought, desertification, and climate change

Desertification, and climate change: the case for greater convergence

Poor knowledge of links between desertification and globalclimate change is limiting funding from the Global Environment Facility foranti-desertification projects and realization of synergies between theConvention to Combat Desertification (CCD) and the FrameworkConvention on Climate Change (FCCC). Greater convergence betweenresearch in the two fields could overcome these limitations, improve ourknowledge of desertification, and benefit four areas of global climate changestudies: mitigation assessment; accounting for land cover change in thecarbon budget; land surface-atmosphere interactions; and climate changeimpact forecasting. Convergence would be assisted if desertification weretreated more as a special case in dry areas of the global process of landdegradation, and stimulated by: (a) closer cooperation between the FCCCand CCD; (b) better informal networking between desertification and globalclimate change scientists, e.g. within the framework of theIntergovernmental Panel on Climate Change (IPCC). Both strategies wouldbe facilitated if the FCCC and CCD requested the IPCC to provide ascientific framework for realizing the synergies between them.

Local scale heat advection

Surface processes play an important role in the simulation of desertification and climate change. The present study shows that enhancement of evaporation at a given place is due to surface temperature and wetness inhomogeneities compared to its surroundings. Between any adjacent dry and wet strips the induced advective heat transport changes the available net radiation between sensible and latent heat fluxes. It also accommodates a redistribution of surface energy between two adjacent inhomogeneous surface strips. A combined model of Tarpley (1994) and Ya Guo and Schuepp (1994) about the advective heat transport over dry and wet strips has been tested over Andhra Pradesh. Taking the Ananthpur district as a relatively drier region, the induced transport over the rest of the districts is estimated. This study has been done for two monsoon seasons of 1990 and 1991. Attempts are made to identify an indexing criteria based on this study to estimate the magnitude of the heat transport.

Desertification hazard and farming-grazing sustainable development in Lingwu-Yanchi region of Ningxia

In the view of the desertification hazard process in Lingwu-Yanchi region of Ningxia Hui Autonomous Region, the paper analyzed the interaction between the physical environment and the human activities, and discussed the social problems of controlling sandy land by using the way of “decreasing farming for increasing grazing” and developing agriculture and animal husbandry. The results indicated that the changes of desertification in the Quaternary geological periods was a kind of climatic geomorphic processes, and a kind of climate-human processes in human history, which are mainly controlled by climatic conditions and partly interfered by human economic activities. Both of the physical-environment and the human activities have double effects to aggravate or reverse the desertification.

Impact of desertification on temperature trends in the Middle East

The intense interest in desertification and climate change has stimulated detailed studies of temperature records in many areas of the world. In this investigation, the temperature records from the Middle East region are analyzed over the period 1950-1990. Results reveal a linear, statistically significant temperature increase of 0.07 °C/decade over the 41-year period. An analysis of spatial controls on these temperature changes reveals a warming effect associated with both overgrazing and the degree of human-induced desertification. The results of this study are consistent with theoretical and empirical studies predicting and demonstrating a warming signal associated with these land surface changes in the world's dryland areas.

The Quality of Life: What Quality? Whose Life?

As a consequence of industrialization, we face unprecedented pressures on the carrying capacity of the earth. Desertification, pollution and global climate changes can only increase these pressures, and will cause vast increases in the number of refugees and widespread risks to human health. Increasing inequalities between rich and poor nations are potential causes of conflict. Since the industrial countries are mainly responsible for our economic problems, they must give a lead in global arrangements to alleviate them. A major change in our habitual patterns of thought is essential, in which we reassess how we perceive values, and how we measure wealth and well-being. This must be accompanied by governmental action: on population numbers and the refugee problem; on the efficient use of energy; on new methods of land use, and on regulation of damaging industrial activities. To act in these ways, governments must reorganize their domestic policies and increase international co-operation.