Desertification Processes Research Articles

Dynamic Monitoring of Desertification in Ningdong Based on Landsat Images and Machine Learning

The ecological stability of mining areas in Northwest China has been threatened by desertification for a long time. Remote sensing information combined with machine learning algorithms can effectively monitor and evaluate desertification. However, due to the fact that the geological environment of a mining area is easily affected by factors such as resource exploitation, it is challenging to accurately grasp the development process of desertification in a mining area. In order to better play the role of remote sensing technology and machine learning algorithms in the monitoring of desertification in mining areas, based on Landsat images, we used a variety of machine learning algorithms and feature combinations to monitor desertification in Ningdong coal base. The performance of each monitoring model was evaluated by various performance indexes. Then, the optimal monitoring model was selected to extract the long-time desertification information of the base, and the spatial-temporal characteristics of desertification were discussed in many aspects. Finally, the factors driving desertification change were quantitatively studied. The results showed that random forest with the best feature combination had better recognition performance than other monitoring models. Its accuracy was 87.2%, kappa was 0.825, Macro-F1 was 0.851, and AUC was 0.961. In 2003–2017, desertification land in Ningdong increased first and then slowly improved. In 2021, the desertification situation deteriorated. The driving force analysis showed that human economic activities such as coal mining have become the dominant factor in controlling the change of desert in Ningdong coal base, and the change of rainfall plays an auxiliary role. The study comprehensively analyzed the spatial-temporal characteristics and driving factors of desertification in Ningdong coal base. It can provide a scientific basis for combating desertification and for the construction of green mines.

Mapping Cork Oak Mortality Using Multitemporal High-Resolution Satellite Imagery

In the Mediterranean region, a significant decline in the vitality of vegetation has been observed in the last two decades, with a high forest mortality rate for several species. The increase in mortality has been attributed to water stress resulting from an increase in temperature and long periods of drought. To detect and quantify the impact of these events on tree mortality, an efficient and easy-to-use methodology for rapid damage assessment is required. Our study aims to assess the potential of high spatial resolution multispectral images from the Pleiades constellation to detect and map cork oak mortality in a pasture environment with multiple forest species. An approach based on change detection and the use of an unsupervised classifier is proposed to detect mortality at the cork oak level. The change in the values observed for three vegetation indices, NDVI, RGI, and GNDVI, between two epochs is used in an unsupervised classification algorithm to estimate the dead tree class. The classification results are accurate, with precision and recall values higher than 90%. Detailed cork oak mortality mapping is of significant use in comprehending ecosystem change as a result of tree mortality and for the implementation of mitigation mechanisms for the ongoing desertification process.

Groundwater regulation for coordinated mitigation of salinization and desertification in arid areas

Desertification and salinization are both threats to the ecosystem services in inland river oases of arid regions. Previous studies focus on either desertification or salinization, and there is a lack of joint studies on the two issues. The essential cause of desertification in a transition zone is usually concentrated irrigation water use, which leads to shrink of the subsurface flow field of groundwater, decline of the groundwater level, and loss of groundwater supply to the vegetation. The salinization problem in an oasis area is mainly caused by the local excess groundwater in the oasis, referring to secondary salinization, which leads to salt migration with the groundwater level rise to form salt crystallization at the land surface. Thus, the processes of desertification and secondary salinization are connected, and the solutions to the two problems can be complementary, i.e., by transporting the excess groundwater in the local secondary salinization area to the transition zone area where water is scarce. This paper, taking Luocheng Irrigation District in the Heihe River Basin of northwestern China as an example, estimates 1.76–4.70 million m3 of excess groundwater that can be extracted in the salinized area. Using this amount of water through engineering regulation, it is estimated that the transition zone nearby the irrigation district, which is under desertification threat, can be restored with an area of 23–212 km2. An engineering system is designed for coordinated groundwater regulation and the implementation with an experimental farm in the irrigation district is demonstrated.

Unfolding the Success of Positive Human Interventions in Combating Land Degradation

A global challenge to sustainable development is land degradation, and to achieve land degradation neutrality, monitoring, mapping, and impact assessment of ongoing ecological restoration efforts is necessary. Here, we analyze the desertification process and role of restoration projects at a spatial and temporal scale in Mu Us Desert from 2001 to 2018. We used 17 years of data to (1) assess the vegetation trend including its significance and map land degradation based on Sustainable Development Goal Indicator 15.3.1 (2) address how vegetation activity has changed under the influence of restoration programs and climate change (3) estimate how successful are the positive human interventions to achieve Land degradation neutrality. Results showed an overall increasing vegetation trend (85.69% significant increasing) and a partial decreasing vegetation trend (1.33% significant decreasing) in Mu Us desert. Ecological restoration activities are found to be one of the key driving forces of vegetation restoration in the desert, however, limited impact of climatic factors on vegetation cover change was observed. Results revealed that 41.42% of total significant restoration is attributed to ecological restoration programs out of which 40.42% area has shown improvement in all three sub-indicators of land degradation.

Inverse modeling of the 2021 spring super dust storms in East Asia

Abstract. Last spring, super dust storms reappeared in East Asia after being absent for one and a half decades. The event caused enormous losses in both Mongolia and China. Accurate simulation of such super sandstorms is valuable for the quantification of health damage, aviation risks, and profound impacts on the Earth system, but also to reveal the climatic driving force and the process of desertification. However, accurate simulation of dust life cycles is challenging, mainly due to imperfect knowledge of emissions. In this study, the emissions that lead to the 2021 spring dust storms are estimated through assimilation of MODIS AOD and ground-based PM10 concentration data simultaneously. With this, the dust concentrations during these super storms could be reproduced and validated with concentration observations. The multi-observation assimilation is also compared against emission inversion that assimilates AOD or PM10 concentration measurements alone, and the added values are analyzed. The emission inversion results reveal that wind-blown dust emissions originated from both China and Mongolia during spring 2021. Specifically, 19.9×106 and 37.5×106 t of particles were released in the Chinese and Mongolian Gobi, respectively, during these severe dust events. By source apportionment it was revealed that the Mongolian Gobi poses more severe threats to the densely populated regions of the Fenwei Plain (FWP) and the North China Plain (NCP) located in northern China than does the Chinese Gobi. It was estimated that 63 % of the dust deposited in FWP was due to transnational transport from Mongolia. For NCP, the long-distance transport dust from Mongolia contributes about 69 % to the dust deposition.

Identification of levels of anthropization and its implications in the process of desertification in the Caatinga biome (Jeremoabo, Bahia-Brazil)

Desertification is one of the most serious current environmental problems and corresponds to the impoverishment and decrease of moisture in sandy soils located in regions with a sub-humid, arid and semiarid climate, with its main causes related to climatic variations and the resulting negative impacts of human activities. Studies show that the soils located in the Brazilian semiarid and especially in the Caatinga biome have been suffering an intense process of desertification due to the replacement of natural vegetation as a result of economic activities. Most municipalities that have an economy based on agropastoral activities are at the centre of desertification in several centres in Brazil. Based on this context and considering that the original vegetation cover is a preponderant factor for soil conservation, and subsequently for the maintenance of the ecological stability of the Caatinga biome, this work aimed to map the vegetation cover of the Vaza-Barris watershed corresponding to the municipality of Jeremoabo (Bahia-Brazil), with the purpose of identifying and quantifying, in terms of surface, the main types of interaction between human activities and the remnants of the vegetation cover, listing the potential impacts that have a direct consequence on the desertification processes. The delimitation of the vegetation cover was the result processing Sentinel 2A satellite images and the use of the Soil Adjusted Vegetation Index - SAVI. Five thematic classes representative of the study area were identified, classified according to the increasing level of anthropization that allowed us to conclude that desertification causes damage to agriculture, making the areas unproductive, as well as excessive agriculture with inappropriate practices causes the loss of fertility of the soils, aggravating the desertification process. With this, the environmental and social quality is threatened, considering that the main source of income in the municipality of Jeremoabo comes from agricultural activities and these are dependent on climatic conditions, soil conservation and water resources.

Desertification and Degradation Risks vs Poverty: A Key Topic in Mediterranean Europe

Land degradation and, subsequently, desertification processes are conditioned by biophysical factors and human impacts. Nowadays, there is an increasing interest by social scientists to assess its implications. Especially, it is relevant to the potential changes and landscape deterioration on population, economic systems and feedbacks of local societies to such adjustments. Assessing social facets should also be related to desertification risks, integrated socio-economic inputs and environmentally sustainable development perspectives. However, investigations about the effects of land degradation conditioned by global socioeconomic-factors from a holistic point of view are scarce. In this review, we pretend to discuss past and recent findings on land degradation risks related to poverty, especially based on Mediterranean Europe. To achieve this goal, we focused on key socioeconomic forces such as developmental policy, production and market structure, social change and population mobility. Our review showed that regional disparities based on complex dynamics of demographic forces (e.g. migration, fertility and ageing) and economic drivers of change (e.g. industrial concentration, urbanization, crop intensification, tourism pressure, coastalization) are keys to understand Mediterranean regions such as Southern Italy, a region exposed to high desertification risk in Europe. We concluded that the overexploitation of territories, soil and water degradation urban expansion, tourism and unplanned industrialization are some sectors and activities which can be highly affected by political and socioeconomic forces leading to unsustainable forms of land management and types of development. Special attention should be paid to social policies, education and training schemes to reduce rural migration and potentiate territorial knowledge to avoid land degradation, considering other social issues such as poverty or centralization. The potential role of win-win policies abating poverty and reducing desertification risk is evident in Mediterranean Europe and achieving land degradation neutrality necessary.

Synergic effects of land-use management systems towards the reclamation of Aeolian Desertified Land in the Shiyang River Basin

Achieving zero land degradation neutrality in Aeolian Desertified Land (ADL) is a challenging task that requires continuous scientific understanding and technical efforts to effectively manage natural resources for economic development while meeting environmental needs. This study used Landsat collection and annual average climate data from the growing season to investigate the efficacy of established land management policies to restore degraded land and reverse the aeolian desertification process in the Shiyang river basin between 1974 and 2020. The time-series Normalized Difference Vegetation Index (NDVI) results revealed that greening and browning trend patterns depend on climatic conditions in rangelands and water allocation management systems in farmlands. Thanks to land rehabilitation and watershed management projects, farmland has been extended to 3.1%, shifting sand area has been reduced to 9.2%, and water in Qingtu lake area re-emergedfrom 0 to 17.05 Km2 in the early 2010 s. Built-up areas also extended to 87.05 km2 between 2010 and 2020 due to extensive construction of solar power panels in the area. The severity of desertification is profoundly linked to climate and land-use management systems in the Shiyang river basin. Moreover, the ADL area declined from 14.65% to 10.74% of the entire river basin, where intensity has steadily reversed in several basin parts, mainly in the middle reach. Around 2248 km2 of land were entirely rehabilitated, 2298 km2 remained steady, 1706 km2 exhibited a reverse in desertification intensity, 199 km2 degraded, and 277 km2 of land were newly turned into ADL between 1974 and 2020, with a large portion of degraded land occurred in the lower reach of the Basin. These findings highlight land management contribution, rational water allocation, and conservation measures to reverse desertification and maintain a sustainable ecosystem despite climate change impacts and water resources shortage in the Shiyang river basin. This research will help decision-makers set up novel land management programs for better eco-environment development in the future.

Ecological Impacts of Land Use Change in the Arid Tarim River Basin of China

Land use/cover change has become an indispensable part of global eco-environmental change research. The Tarim River Basin is the largest inland river basin in China. It is also one of the most ecologically fragile areas in the country, with greening and desertification processes coexisting. This paper analyzes the evolution of land-use/cover change in the Tarim River Basin over the past 30 years based on remote sensing data. The research also explores the contribution of conversion between different land types to the ecological environment by selecting methods, such as transfer matrix and ecological contribution rate. Results indicate that grassland and barren land are the main land types in the region, accounting for 72.46% and 18.87% of the basin area, respectively. From 1990 to 2019, cropland area increased from 33,585.89 km2 to 52,436.40 km2, an increase of 56.13%, while barren land areas decreased from 781,380.57 km2 to 760,783.29 km2. Most of the land-use conversion was grassland to other land types and other land types to barren land. Since 1990, the conversion of barren land to grassland and cropland in the basin has led to ecological improvement, whereas the conversion of grassland to cropland has caused deterioration, but with a generally improving trend. It is anticipated that, over the next decade, changes in land types will involve increases in grassland and woodland area, decreases in barren land and cropland, and an overall improvement in the ecological environment in the watershed. Since agriculture and animal husbandry are the main industries in the Tarim River Basin and the land-use structure is dominated by cropland and grassland, several key measures should be implemented. These include improving land use, rationalizing the use of water and soil resources, slowing down the expansion of cropland, and alleviating the contradiction between humans and land, with the ultimate aim of achieving sustainable development of the social economy and ecological environment.

Spatiotemporal variations in surface water and its significance to desertification in China from 2000 to 2019

Dynamics in surface water area (SWA) and its impacts on desertification are poorly understood in the desertification-prone region (DPR) of China. We defined 2440 sub-watersheds at the fifth-order level in China’s DPR, and investigated the spatiotemporal variations in SWA and their substantial driving factors (such as temperature, precipitation, evaporation, and irrigation activity). The results showed that the average annual maximum SWA was 7165 km2 in DPR from 2000 to 2019, of which 84% was the seasonal SWA. The seasonal and permanent SWA increased by 188 km2 yr−1 and 46 km2 yr−1, respectively. The SWA in non-DPR was the dominant driving factor for SWA dynamics in most basins except for HunlunBuir, Otindag and Ordos, where the irrigation activity showed significant contributions to SWA variations. Climate had a relatively low contribution to SWA variations in DPR. The role of SWA variations on desertification processes in DPR of China showed significant spatiotemporal differences from 2000 to 2019. The increased SWA promoted reversal of desertification in watersheds along the Tarim River, northwestern Junggar, eastern Ordos, and parts of Otindag, however, it did not help in northwestern Qinghai. Our findings provide a scientific insight into the characteristics of surface water resources and the relationship between SWA dynamics and desertification in the DPR of China.

Found in Complexity, Lost in Fragmentation: Putting Soil Degradation in a Landscape Ecology Perspective.

The United Nations Convention to Combat Desertification (UNCCD) assumes spatial disparities in land resources as a key driver of soil degradation and early desertification processes all over the world. Although regional divides in soil quality have been frequently observed in Mediterranean-type ecosystems, the impact of landscape configuration on the spatial distribution of sensitive soils was poorly investigated in Southern Europe, an affected region sensu UNCCD. Our study proposes a spatially explicit analysis of 16 ecological metrics (namely, patch size and shape, fragmentation, interspersion, and juxtaposition) applied to three classes of a landscape with different levels of exposure to land degradation (‘non-affected’, ‘fragile’, and ‘critical’). Land classification was based on the Environmentally Sensitive Area Index (ESAI) calculated for Italy at 3 time points along a 50-year period (1960, 1990, 2010). Ecological metrics were calculated at both landscape and class scale and summarized for each Italian province—a relevant policy scale for the Italian National Action Plan (NAP) to combat desertification. With the mean level of soil sensitivity rising over time almost everywhere in Italy, ‘non-affected’ land became more fragmented, the number of ‘fragile’ and ‘critical’ patches increased significantly, and the average patch size of both classes followed the same trend. Such dynamics resulted in intrinsically disordered landscapes, with (i) larger (and widely connected) ‘critical’ land patches, (ii) spatially diffused and convoluted ‘fragile’ land patches, and (iii) a more interspersed and heterogeneous matrix of ‘non affected’ land. Based on these results, we discussed the effects of increasing numbers and sizes of ‘critical’ patches in terms of land degradation. A sudden expansion of ‘critical’ land may determine negative environmental consequences since (i) the increasing number of these patches may trigger desertification risk and (ii) the buffering effect of neighboring, non-affected land is supposed to be less efficient, and this contains a downward spiral toward land degradation less effectively. Policy strategies proposed in the NAPs of affected countries are required to account more explicitly on the intrinsic, spatio-temporal evolution of ‘critical’ land patches in affected regions.

‘Old’ Territorial Disparities and ‘New’ Spatial Patterns: Unraveling the Latent Nexus between Sustainable Development and Desertification Risk in Italy

Although sustainable development and desertification risk are hegemonic concepts in environmental economics, their intimate relationship was occasionally studied and made spatially explicit. The present study contributes to fill this knowledge gap by delineating a statistical procedure that investigates, at the municipal scale in Italy, the association between two composite indexes of sustainable development (SDI) and desertification risk (ESAI). Based on a refined knowledge of the local context, results of a geographically weighted regression delineate two distinctive territorial models reflecting the mutual interplay of sustainable development and desertification risk in Italy. The level of sustainable development was negatively associated with desertification risk in Southern Italy, a region classified as ‘affected’ based on the Italian National Action Plan (NAP) to combat desertification. These findings document a traditional ‘downward spiral’ between local development and early desertification processes, suggesting that a high desertification risk is associated with local contexts having structural conditions that lead to unsustainable development, e.g., population growth, industrial development, tourism pressure, crop intensification, agricultural mechanization, and land abandonment. In non-affected regions such as Northern and Central Italy, the level of sustainable development was positively associated with desertification risk, indicating that sustainability conditions can be unable, at least in some local contexts, to assure a significant containment of environmental degradation. Policy strategies reconnecting local development with more specific environmental conservation targets in development countries are increasingly required to adapt to (and differentiate on the base of) heterogeneous local contexts.

Desertification in Spain: A Sound Diagnosis without Solutions and New Scenarios

The latest world atlas of desertification represents a turning point in the diagnosis of desertification. While it forgoes desertification mapping due to the intrinsic complexity of the phenomenon and the impossibility of measuring it using a single indicator, it introduces the convergence of evidence paradigm, which identifies socioeconomic and biophysical variables whose behaviour allows pointing out those areas prone to desertification. The Spanish National Action Program Against Desertification (PAND), back in 2008, already implemented a similar approach to identify five “desertification landscapes” within Spain using both socio-economic and climatic information. The PAND was not only pioneering but also, unfortunately, accurate. Desertification in Spain has continued to worsen and the first two decades of the 21st century have consolidated an agri-food model whose dynamics have exacerbated the desertification processes identified in the PAND. Despite its scientific value, the PAND lacked a proper action plan and was completely detached from the diagnosis. As a result, the diagnosis it provided was not followed by effective actions to halt desertification in Spain. The Spanish government’s recent declaration of climate and environmental emergency requires a new strategy to combat desertification. This commitment is an excellent opportunity to update the diagnosis of the situation and, more crucially, to unify the different desertification sectoral policies and actions under a single front. We provide here elements (e.g., analysis of agri-food trends and integration of plans and policies at different geographical and sectoral levels) for a roadmap to be designed around the pressures, impacts, and drivers that define today’s Spanish desertification landscapes to effectively manage and avoid their further degradation.

“Fertile islands” beneath three desert vegetation on soil phosphorus fractions, enzymatic activities, and microbial biomass in the desert-oasis transition zone

Desertification poses a perpetual threat to the security of desert ecosystems. Perennial desert vegetation plays a crucial role in maintaining the structure and function of a desert ecosystem and slowing down its desertification process by creating “fertile islands” beneath their canopy. Yet, how these fertile islands affect the transformation of soil phosphorus (P) fractions and the relationship between soil P fractions and enzymatic activities or microbial biomass beneath differing plant species and across soil depths still remains uncertain. Here we collected and analyzed soil P fractions (Hedley P pools), enzymatic activities (alkaline phosphatase [ALP] and β-glucosidase), microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus, in addition to other soil properties, beneath three typical perennial species (Alhagi sparsifolia, Karelinia caspia, Tamarix ramosissima) and in interspace area soils over a 0–100 cm soil profile, under the desert-oasis transition zone of hyper-arid and soil P-impoverished. We found that soil P fractions, especially soil labile-P, soil enzymatic activities, soil water content (SWC), NH4+-N and NO3−-N concentration were closely related to the soils beneath canopy than interspace area. Soil depth and plant species also significantly affected soil labile-P and other soil properties, with the highest being topsoil beneath the canopy. Soil labile-P increased substantially beneath the canopy and was positively related to the activities of ALP and β-glucosidase and the concentrations of soil MBC and MBN, while negatively related to SWC and electrical conductivity. We also observed that the fertile island effect was generally consistent with canopy size and ranked as follows: T. ramosissima > K. caspia > A. sparsifolia. This comprehensive field study advances our current understanding of the transformation of soil P fractions vis-à-vis the fertile island effect in desert ecosystems, which could be useful for mitigating desertification by improving soil protection and greening the desert landscape.

Assessing Land Cover and Ecological Quality Changes in the Forest-Steppe Ecotone of the Greater Khingan Mountains, Northeast China, from Landsat and MODIS Observations from 2000 to 2018

Land cover changes are the main factors driving the evolution of regional ecological quality. These changes must be considered in the strategic formulation of regional or national ecological policies. The forest-steppe ecotone in the Greater Khingan Mountains is an important ecological barrier in northern China. To measure the effect of ecological protection in recent years, Landsat images, object-oriented image segmentation, and convolutional neural networks were used to create land cover datasets of the forest-steppe ecotone. The Carnegie–Ames–Stanford approach (CASA) and the dimidiate pixel model were used to derive net primary productivity (NPP) and fractional vegetation cover (FVC) to assess the ecological quality of this area. The results showed that only grassland and urban land increased, whereas saline–alkali land and desert areas initially increased and then decreased from 2010 to 2018, indicating that the desertification process was substantially curbed. Total NPP increased by 26.3% (2000–2010) and 10.8% (2010–2018). However, NPP decreased slightly in the center of the study area. FVC first decreased and then increased, and the increased areas were concentrated in the forest-steppe ecotone, saline–alkali land, and desert zone in Xin Barag Left Banner. These observations indicate that the ecological quality has gradually improved due to the strict protection of forest and grassland resources and the suppression of desertification. Our results provide potential insights for land use planning and the development of environmental protection measures in the forest-steppe ecotone.

Effects of Climate Change and Human Activities on Aeolian Desertification Reversal in Mu Us Sandy Land, China

The aeolian desertification in Mu Us Sandy Land (MUSL) in northern China have been paid much attention, but the relative contributions of climate change and human activities to desertification dynamics are still not clear. Based on the Landsat MSS, TM, ETM+ and OLI images in 1975, 1990, 1995, 2000, 2005, 2010 and 2015, we developed a database of aeolian desertification land distribution, discussed the spatial and temporal variation of aeolian desertification, and discovered the relative contributions of climate change and human activities to desertification reversal, using the trends of the potential net primary productivity (NPP) and the human-influenced NPP with meteorological data and MODIS NPP products. The results indicated that aeolian desertification developed firstly from 1975 to 2000, with serious and severe aeolian desertification land continually increasing, and then changed into a reversal state from 2000 to 2015, as the serious aeolian desertification land decreased, although the severe, moderate and light aeolian desertification land lightly increased. Human activities were the dominant factor in desertification dynamics in MUSL and had different contributions to aeolian desertification reversal in different periods. This study will improve our understanding of the processes of aeolian desertification.

The current state of pastures in Western Kazakhstan, depending on the method of their use

The process of pasture resources management in Western Kazakhstan is complicated by the deterioration of vegetation cover with the manifestation of degradation and desertification processes as a result of unsystematic grazing. The aim of the research is to study distant pasture grazing on the productivity of pastures for their rational use. Field experiments were carried out in 2018–2021 on the pastures of the semi-desert zone of the Western Kazakhstan region on the territories of the “Miras” peasant farm in the Bokeyurdinsky district. As experimental plots, 4 pastures were selected, used in different ways: unsystematic, seasonal and distant pastures. 3 pasture areas are located on the relief part of the semi-desert zone, and the distant-pasture area is located in the sandy part of Ryn-Peski. To study the influence of the methods of use on the productivity of pastures on the polygon areas, regular observations of the quantitative and qualitative parameters (projective cover, height, species composition, yield) of phytocenoses were carried out. The research allowed to prove the seasonal organization of pasture economy using the distant pasture. In the summer period, an increase in the number and occurrence of valuable pasture plants Kochia prostrata, Agropyron desertorum, Festuca valesiaca, Leymus ramosus, Koeleria cristata was noted on seasonal pastures. On the distant site of sandy pastures, 23 plant species of different economic and botanical groups have been determined, and due to the natural conditions of sands in the phytocenosis, the occurrence of valuable plants in the forage ratio was high. By the middle of summer, in the area of seasonal and distant pastures, despite the loss of forbs from the vegetation composition and drying of cereals, the yield of green phytomass was 8.09–10.25 c/ha, which is higher than in the area of unsystematic grazing by 4.28–6.44 c/ha. In this work, it was concluded that to improve the efficiency of pasture resource management, it is important to use seasonal pastures with the inclusion of a distant site in pasture rotation, which is the scientific novelty of the research.

Assessment of environmentally sensitive areas to desertification in the Blue Nile Basin driven by the MEDALUS-GEE framework

Assessing environmentally sensitive areas (ESA) to desertification and understanding their primary drivers are necessary for applying targeted management practices to combat land degradation at the basin scale. We have developed the MEditerranean Desertification And Land Use framework in the Google Earth Engine cloud platform (MEDALUS-GEE) to map and assess the ESA index at 300 m grids in the Blue Nile Basin (BNB). The ESA index was derived from elaborating 19 key indicators representing soil, climate, vegetation, and management through the geometric mean of their sensitivity scores. The results showed that 43.4%, 28.8%, and 70.4% of the entire BNB, Upper BNB, and Lower BNB, respectively, are highly susceptible to desertification, indicating appropriate land and water management measures should be urgently implemented. Our findings also showed that the main land degradation drivers are moderate to intensive cultivation across the BNB, high slope gradient and water erosion in the Upper BNB, and low soil organic matter and vegetation cover in the Lower BNB. The study presented an integrated monitoring and assessment framework for understanding desertification processes to help achieve land-related sustainable development goals.

Геоинформационное картографирование соровых понижений в Северо-Западном Прикаспии

The article discusses the results of mapping sor depressions in the Sarpinskaya lowland based on geoinformation technologies and Sentinel-2 satellite data. The research area is subject to desertification processes, which are expressed in a decrease in the productivity and density of vegetation up to its complete destruction as a result of uncontrolled pasture loads and climatic fluctuations. The consequence of these processes is an increase in the area of shifting sands, intensification of dust storms and economic losses. For these reasons, it is extremely important to timely determine the centers of desertification in order to take measures to limit pasture loads on them and carry out phytomelioration. Satellite data are widely used to monitor desertification processes. However, the presence of natural areas devoid of vegetation due to their genesis—solonchaks and sors—is practically not considered. Attributing these categories to desertification is incorrect; for this reason, they should be mapped separately and not considered in the future. Sory (sor depressions) is a closed arid drainless landform with a temporary drying up reservoir. The area of sor depressions is constant; only the ratio of areas of water, salt crust, mud, and vegetation along the periphery changes. As the water dries up and forms a white salt crust during the growing season, the albedo of the sor surface increases, due to which they can be classified as lands subject to desertification in the classification of satellite images. In total, as a result of the work, about 7 thousand objects were identified: sors, solonchaks and dry ilmens with a total area of 143 thousand hectares. More than half of the total share of all depressions has an elongated shape in the sublatitudinal direction. Sor depressions with a depth of 1–2 m predominate compared to the surrounding area. There are also salt marshes that are not expressed in relief or rise up to 1 m above the surroundings. The results obtained can be used in geomorphological and soil studies and will also allow more accurate satellite monitoring of desertification processes in the region.

ГЕОЭКОЛОГИЧЕСКОЕ СОСТОЯНИЕ ВОДНЫХ ОБЪЕКТОВ В РЕСПУБЛИКЕ КАЛМЫКИЯ

Purpose: assessment of the geoecological state of water bodies, large irrigation and feeding systems, Sarpinsky lakes, reservoirs, main and distribution canals, river network. The total area of irrigation and feeding systems totals about 122 thousand hectares, while half of the 54 thousand hectares of irrigated land is watered with high salinity water. For 48 years, the morphometric characteristics of large lakes have changed for the worse, the water in the lakes is gradually becoming saline, the coastal zone is overgrown with aquatic vegetation and is significantly silted up, many irrigation canals experience slope deformations, their dams are being destroyed, and the throughput capacity is decreasing. About 135 reservoirs have been built on the territory of Kalmykia, the largest of which are Chograyskoe, Gorodovikovskoe and Proletarskoye. Condition of irrigated lands for the period 2010–2018 is assessed as good in 2–4 % of cases, as satisfactory in 24–29 %, as unsatisfactory in 68–72 % of cases. Discussion. The cause of secondary salinization, waterlogging, depletion of irrigated lands and desertification was the imperfection of irrigation and collector-drainage systems, as well as irrigation techniques. The inclusion of a large amount of fallow lands in agriculture will lead to socio-economic and climatic changes, as well as humid warming in the Republic of Kalmykia. In the future, it is recommended to reconstruct canals in an earthen channel with the installation of lining on them using geosynthetic and geocomposite materials, which will increase the canals’ performance of the Chernozemelskaya and partially Sarpinskaya watering and feeding systems, bringing their efficiency to 0.85–0.90. Conclusions. Desertification processes are developing in the Republic of Kalmykia, the main causes of which are degradation, wind and water soil erosion, dehumification and secondary salinization. The total desertification index is 76 points.