Climate Change In Arid Regions Research Articles

Predicting the impact of climate change on crop water footprint using CMIP6 in the Shule River Basin, China

Quantitatively predicting the impacts of climate change on water demands of various crops is essential for developing measures to ensure food security, sustainable agriculture, and water resources management, especially in arid regions. This study explored the water footprints (WFs) of nine major crops in the middle and downstream areas of Shule River Basin, Northwest China, from 1989 to 2020 using the WF theory and CROPWAT model and predicted the future WFs of these crops under four emission and socio-economic pathway (SSPs-RCPs) scenarios, which provides scientific support for actively responding to the negative impacts of climate change in arid regions. Results indicated: (1) an increasing trend of the overall crop WF, with blue WF accounting for 80.31–99.33% of the total WF in the last 30 years. Owing to differences of planting structure, water-conservation technologies, and other factors, the multi-year average WF per unit area of crops was 0.75 × 104 m3 hm−2 in downstream area, which was higher than that in midstream area (0.57 × 104 m3 hm−2) in the last 30 years; therefore agricultural water use efficiency in the downstream area was lower than that in the midstream area, implying that the midstream area has more efficient agricultural water utilization. (2) an initial increase and then decrease of crop WFs in the study area under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios by the end of the century, reaching their peak in 2030s which was higher than that from 1989 to 2020; with the maximum growth rates in the midstream area ranging from −0.85% in SSP5-8.5 to 5.33% in SSP2-4.5 and 29.74% in SSP5-8.5 to 34.71% in SSP2-4.5 in the downstream area. The local agricultural water demand would continue to increase and water scarcity issues would be more severe in the next 10–20 years, affecting downstream areas more. Under the SSP3-7.0 scenario, crop WF values of the midstream and downstream regions will be 2.63 × 108 m3 and 4.22 × 108 m3 in 2030, respectively, which is significantly higher than those of other scenarios and show a long-term growth trend. The growth rate of the midstream and downstream regions will reach 44.71% and 81.12%, respectively, by the end of this century, so the local agricultural water use would be facing more strain if this scenario materializes in the future. Therefore, the Shule River Basin should encourage development of water-saving irrigation technologies, adjust the planting ratio of high water consuming crops, and identify other measures to improve water resource utilization efficiency to cope with future water resource pressures.

Comparisons of climate change characteristics in typical arid regions of the Northern Hemisphere

In recent years, with the frequent occurrence of severe drought events, climate change in arid regions has become one of the research hotspots. However, previous studies mainly focused on a specific arid region, and the correlations and differences of drought among various arid regions have not been clearly understood. In this study, based on the latest monthly gridded dataset of the CRU, we compare the characteristics of climate change and its relationship with large-scale oceanic oscillation indexes in the three typical arid regions of Pan-Central-Asia (PCA), North America (NAm) and North Africa (NAf) in multiple perspectives. The results show that the precipitation in the PCA and NAm has increased obviously over the past 80 years, while the NAf precipitation has decreased. After the 1980s, the climate in the PCA and NAm show warm-wet types. This type of the former continues to the present, but the latter’s has changed to a warm-dry type since the 21st century. The NAf climate remains the warm-dry type since the 1990s. Nonetheless, the arid and semi-arid climate patterns in the three typical arid regions remain unchanged. The NAm precipitation has an anti-phase variability pattern compared with the NAf precipitation on both interdecadal and multi-decadal time scales. The Pacific Decadal Oscillation (PDO) has a great influence on the precipitation of the PCA and NAm. The temperature of three arid regions is significantly related to the variations in the Arctic oscillation (AO). In the inland arid region, the contribution of strong warming effect during cold season to the whole year is much greater than that during warm season, while the contribution of the coastal arid regions in warm season is greater. The precipitation in the mid-latitude arid regions is dominated by cold-season precipitation regardless of whether these regions are near the sea or not. The precipitation in the low-latitude arid regions has little difference between cold and warm seasons.

Relationships Between Soil Microbial Diversities Across an Aridity Gradient in Temperate Grasslands : Soil Microbial Diversity Relationships.

Soil microbes assemble in highly complex and diverse microbial communities, and microbial diversity patterns and their drivers have been studied extensively. However, diversity correlations and co-occurrence patternsbetween bacterial, fungal, and archaeal domains and between microbial functional groups in arid regions remain poorly understood. Here we assessed the relationships between the diversity and abundance of bacteria, fungi, and archaea and explored how environmental factors influence these relationships. We sampled soil along a 1500-km-long aridity gradient in temperate grasslands of Inner Mongolia (China) and sequenced the 16S rRNA gene of bacteria and archaea and the ITS2 gene of fungi. The diversity correlations and co-occurrence patterns between bacterial, fungal, and archaeal domains and between different microbial functional groups were evaluated using α-diversity and co-occurrence networks based on microbial abundance. Our results indicate insignificant correlations among the diversity patterns of bacterial, fungal, and archaeal domains using α-diversity but mostly positive correlations among diversity patterns of microbial functional groups based on α-diversity and co-occurrence networks along the aridity gradient. These results suggest that studying microbial diversity patterns from the perspective of functional groups and co-occurrence networks can provide additional insights on patterns that cannot be accessed using only overall microbial α-diversity. Increase in aridity weakens the diversity correlations between bacteria and fungi and between bacterial and archaeal functional groups, but strengthens the positive diversity correlations between bacterial functional groups and between fungal functional groups and the negative diversity correlations between bacterial and fungal functional groups. These variations of the diversity correlations are associated with the different responses of microbes to environmental factors, especially aridity. Our findings demonstrate the complex responses of microbial community structure to environmental conditions (especially aridity) and suggest that understanding diversity correlations and co-occurrence patternsbetween soil microbial groups is essential for predicting changes in microbial communities under future climate change in arid regions.

Simulating winter wheat production potential under near-future climate change in arid regions of northeast Iran

Simulating winter wheat production potential under near-future climate change in arid regions of northeast Iran

Treated wastewater for meeting challenges of climate change in arid regions

This paper focuses on treated wastewater in addressing the impacts of climate change on water sources, especially in arid and semi-arid regions that suffer anyway from water scarcity. Jordan with its severe water situation is expected to be defenseless to climate change effects taking into account the unbalance between available water resources and urgent demands. The paper helps in assessing treated wastewater as an effective adaptation measure to cope with water scarcity in Jordan and to consider it as an integral part of the national water budget. Wastewater is a promising alternative to cover the shortage in water supply in regions where severe drought is an anticipated effect of climate change, also to provide water of good quality to secure drinking water for the population, at the same time to increase the efficiency of the uses of the available water sources. Jordan has 36 wastewater treatment plants in operation scattered throughout the country and producing about 430,000 CM/day of reclaimed wastewater. According to the reports Ministry of Water and Irrigation, more than 85 percent of this water is of in full compliance to the quality required for irrigation of field crops and forest trees according to JS 893/2006.

An inverse relationship between moisture and grazing intensity in an arid mountain-basin system

Precipitation has been suggested as a crucial influencing factor in the primary productivity in arid and semi-arid regions, yet how moisture fluctuation in an arid mountain-basin system of the north Qinghai–Tibetan Plateau has affected human activities is poorly understood. Here, we reconstruct the variations of grazing intensity in high elevations and regional humidity based on independent and high-resolution records of Sporormiella-type coprophilous fungal spores and pollen grains in the same well-dated sediment core from Lake Tian’E in the western Qilian Mountains over the past 3500 years. We find that stronger grazing activity was associated with low regional effective moisture, and propose that the drier regional climate pushed people and their livestock into the mountainous areas. A notable exception was a reduction of human and grazing activities in arid region with high mountains during 380–580 CE caused by centennial-length dry and cold conditions. In addition, it is also noteworthy that intensified grazing activity occurred during 580–720 CE and after ∼1920 CE, corresponding to a warmer and wetter climate and diverse subsistence strategies with social developments in the lowlands of the Hexi Corridor. Our findings potentially provide a historical reference for understanding how ancient people adapted to the climate change in arid region with high mountains.

Impacts of climate change on vegetation phenology and net primary productivity in arid Central Asia

Vegetation is highly sensitive to climate changes in arid regions. The relationship between vegetation and climate changes can be effectively characterized by vegetation phenology. However, few studies have examined the vegetation phenology and productivity changes in arid Central Asia (ACA). The vegetation phenological information of ACA was extracted using MODIS NDVI (Normalized Difference Vegetation Index) data, and the dynamics of vegetation phenological changes under spatiotemporal variations were quantitatively assessed. Moreover, the impacts of climate change on vegetation phenology and net primary productivity were analyzed by combining meteorological data with that of MODIS NPP (Net Primary Productivity) during the same period. The results demonstrated that the start of the season (SOS) of vegetation in the study was concentrated from mid-February to mid-April, while the end of the season (EOS) was concentrated from early October to mid-December. The length of growing season (LOS) ranged from 6 to 10 months. The SOS of vegetation was gradually postponed at a rate of 0.16 d·year−1. The EOS advanced at a rate of 0.69 d·year−1. The LOS was gradually shortened at a rate of 0.89 d·year−1. For each per 1000 m increase in elevation, the SOS of vegetation was postponed by 12.40 d; the EOS advanced by 0.40 d, and the LOS was shortened by 11.70 d. For the impacts of climate changes on vegetation phenology and NPP, the SOS of vegetation phenology negatively correlated with temperature but positively correlated with precipitation and NPP. The EOS and LOS positively correlated with temperature but negatively with precipitation and NPP. Results indicated that the SOS was not moved ahead but was delayed, while the EOS advanced rather than being postponed under climate change. These results can offer new insights on the phenological response to climate change in arid regions and on non-systematic changes in phenology under global warming.

A Combination Forecasting Strategy for Precipitation, Temperature and Wind Speed in the Southeastern Margin of the Tengger Desert

Global warming is inevitably the cause of local climate change, which will have a profound impact on regional ecology, especially in the desertified steppe and steppefied desert transition zones with fragile ecological environments. In order to investigate the change trends of precipitation, temperature and wind speed for effectively realizing the restoration and protection of desert ecosystems, a combination forecasting strategy including the data pre-processing technique, sub-models selection and parameter optimization was proposed and three numerical simulation experiments based on the combination model with the weights optimized by the particle swarm optimization algorithm were designed to forecast the precipitation, temperature and wind speed in the southeastern margin of the Tengger Desert in China. Numerical results showed that the proposed combination prediction method has higher forecasting accuracy and better robustness than single neural network models and hybrid models. The proposed method is beneficial to analyze climate change in arid regions.

Environmental Information Revealed by Sensitive Grain Size Component of Lake Sediments in Longcheng Yardang on the Northeast Edge of Tarim Basin

On basis of grade-standard deviation method, two sensitive grain size components (component 1:5.8∼10.0μm, component 2:60.3∼104.7μm) and a less sensitive grain size component (component 3:15.1μm∼22.9μm) were extracted from the samples of the sedimentary age of LX02 profile, which were collected from Longcheng Yardang region on the northeast edge of Tarim Basin. The study discusses the material sources and action forms of different grain size sensitive components, which can be used as an indicator to reveal the regularity of the lake and the intensity of wind-sand activity respectively. The lacustrine transgressive and regressive history of the region has been reconstructed for 72−51ka B.P. by the characteristics of the content of sensitive grain size component 2, and the palaeoclimate information of the sediments was restored, which provided the basis for exploring the distribution law of other environmental factors in lake sediments. This paper is helpful to explore the law of environmental evolution and the history of climate change in arid regions.

Respuesta hidrológica al cambio climático en regiones áridas: caso de estudio en los Comondú, Baja California Sur, México

Respuesta hidrológica al cambio climático en regiones áridas: caso de estudio en los Comondú, Baja California Sur, México

Quantitative Trend, Sensitivity and Contribution Analyses of Reference Evapotranspiration in some Arid Environments under Climate Change

The temporal trend of reference crop evapotranspiration (ET0) and contribution of associated meteorological factors to the ET0 trend were assessed for 17 arid areas. Sensitivity of ET0 to changes in key meteorological variables was also analyzed. To study temporal trend of ET0, Mann-Kendall trend test was employed. Quantitative contribution and sensitivity analyses were carried out, respectively, using a dimensionless relative sensitivity coefficient and detrending method. Results indicated that ET0 has an increasing trend in 70.6, 64.7, 70.6, 76.5 and 70.0%, of sites respectively, in winter, spring, summer, autumn and entire year. This positive trend was significant (p ≤ 0.05) in 47.0, 35.3, 35.3, 29.4 and 35.3% of sites, respectively, for the same seasons. There was a significant change-point in winter, spring, summer, autumn and annual ET0 series at 64.7, 52.9, 64.7, 64.7 and 82.3% of stations, respectively. In 35.3 and 35.3% of sites, solar radiation and wind speed were the most sensitive climatic factors on ET0, respectively. ET0 exhibited the highest sensitivity to the relative humidity changes in coastal sites. Changes of wind speed contributed much more than other factors to the annual ET0 trend in 58.8% of investigated sites. The negative trend in wind speed nearly nullified the positive effects of increased air temperature on ET0 over 1966–2012 in 23.5% of stations. Changes in ET0 were attributed to wind speed changes in most locations. Given the upward trend of ET0 in the majority of locations, proper water management is required to avoid negative impacts of climate change in arid regions.

The application of polynomial analyses to detect global vegetation dynamics during 1982–2012

ABSTRACTUse of the normalized difference vegetation index (NDVI) to build long-term vegetation trends is one of the most effective techniques for identifying global environmental change. Trend identification can be achieved by ordinary least squares (OLS) analysis or the Theil–Sen (TS) procedure with a Mann–Kendall (MK) significance test, and these linear regression approaches have been widely used. However, vegetation changes are not linear, and thus the response of vegetation to global climate change may follow non-linear trends. In this article, a polynomial trend-fitting method, which uses stepwise regression and expands on previous research, is presented. With an improved fitting ability, this procedure may reveal trends that were concealed by linear fitting methods. Globally, the traditional TS-MK method reveals significant greening trends for 37.27% of vegetated land, and significant browning trends for 7.98%. Using the polynomial analysis, 34.62% of pixels were fitted by high-order trends. The significant greening trends covered up to 30% of cultivated land, thus indicating that cultivated vegetation may be increasing faster than natural vegetation. Significant vegetation browning mostly occurred in sparse vegetation areas, which suggests that vegetation growth may be more sensitive to climate change in arid regions. Our results show that use of polynomial analysis can help further elucidate global NDVI trends.

Adaptation of the agricultural sector to the effects of climate change in arid regions: competitive advantage date palm cropping patterns under water scarcity conditions

This research paper highlights the adverse effects of climate change on the agricultural sector in Saudi Arabia and the actions taken to adapt to these adverse effects. Special focus was given to the potential to optimise the reallocation of scarce water resources among the competitive advantage date palm cropping regions in Saudi Arabia using a mathematical sector modelling approach. The results showed great potential for Saudi Arabia to adapt to the adverse effects of climate change by optimising the date palm cropping pattern in accordance with its scarce water resources and limited cultivated lands. The optimised scenario would result in a high net annual return, equivalent to about 881.76 million US$ year−1, and an increase on the water use return from about 0.97 US$ cm−1 in the base year to approximately 1.31 US$ cm−1. The optimised scenario would also provide the opportunity to reduce the allocated date palm cropping area by approximately 4% (from approximately 118,250 hectares to approximately 113,446 hectares) and to reduce the water demand by approximately 1% (from 681.06 million cubic metres (MCM) per year to approximately 674.28 MCM per year).

A framework for the assessment of reservoir operation adaptation to climate change in an arid region

It is essential to assess the adaptation of reservoir operation to climate change in arid regions. The main objective of this research is to propose a framework for assessment of reservoir rule-curve (RRC) adaptation for climate change scenarios. The framework is applied to an arid zone in Iran and consists of the three models: downscaling, rainfall-runoff and reservoir optimisation models. LARS-WG is tested in 99% confidence level before to using it as downscaling model. Seven artificial neural network models are proposed, examined and compared with IHACRES to find proper rainfall-runoff model for arid zone. Current and adapted reservoir rule curves are derived by dynamic programming optimisation. The results demonstrate capability of proposed framework in assessment of adaptation and show that global warming negatively influences proposed index (water supply index) in normal and wet years, but has positive influence for dry years. It also improves reservoir reliability, but it cannot restore current reliability.

Combating climate change through off-seasonally raising seedling of papaya (Carica papayaL.) in protected environment

Major difficulty of raising papaya seedling is mortality of seedling, among abiotic factors of environment like unfavourable microclimate; especially temperature restricts raising off-season fruit nursery under open field condition in arid region. Papaya (Carica papaya L.) is widely grown fruit crop in tropics and India is the largest producer in the world. Papaya seedlings are fetching very high price during off-season availability. In this study, a low tunnel greenhouse (S1) and black shade net house (S2) were taken as protected structures for growing of papaya seedlings. The variety of papaya seedlings was Madhubindu and soil+FYM was taken as growing media for this study. Survival and growth of seedlings were monitored for 30–60 days. The environmental and morphological data were recorded and computed and response of papaya seedling growth was evaluated in terms of germination percentage, seedling height, collar diameter, number of leaves, diameter of shoot, fresh and dry weight of aboveground and underground biomass, sturdiness, root: shoot ratio, vigour index length andvigour index mass in root media. The results of this study revealed that the environmental factor during the entire study period was found significant in black shade net structure compared to greenhouse. Variation in seedling growth in different microclimatic conditions may be due to the differences in growth behaviour under given set of environmental conditions. The minimum time taken for days of germination, germination percentage, seedling height, collar and shoot diameter was found highest in black shade net house (S2) with variety i. e. Madhubindu and soil+FYM as growing media. Economically black shade net house with net profit 513.27 Rs./m2, BCR 3.94 and payback period 0.59 was found highly suitable for raising seedling of papaya off-seasonally and mitigating climate change in arid region.

The trend of climate and runoff changes in the Ba river basin

A warming planet and changing climate will alter the distribution, volume, timing and type of rainfall, and will modifythe distribution and timing of run-off. Many regions around the world show that climate change is having an overall netnegative impact on water resources and freshwater ecosystems. The impact of climate change on local dischargevariability is considered in the Ba river basin. Ba river basin is the largest basin of the South Central region, located inthe four provinces of Kon Tum, Gia Lai, Dak Lak and Phu Yen, with a catchment area of 13,900 km2.This research applied the Mann-Kendall model to calculate and evaluate the trend of climate and runoff changes inthe Ba river basin. The result of calculation showed the increase of temperature over the Ba basin except the minimumtemperature at An Khe station. In the central of the basin - the dry area - the rainfall tends to decrease while that in thelower area tends to increase. The maximum daily rainfall tends to decrease in almost of the meteorological stationsexcept for the An Khe station. The annual runoff in the Ba river basin tends to increase whereas the maximum river flowtends to decline. The minimum river flow tends to decrease in the lower and increase in the upper area. In particulaly,the maximum and minimum sediments tend to increase in the Ba river basin.ReferencesPhan Thi Thanh Hang, Kengo Sunada,Satoru Oishi, Yasushi Sakamoto, 2010. Climate change and impacts on runoff in the Kone River Basin, Central Vietnam. Proceedings of the Fifth Conference of Asia Pacific Association of Hydrology and Water Resources. pp 221-227.Phan Thi Thanh Hang, Kengo Sunada, Satoru Oishi, Yasushi Sakamoto, 2010. River discharge in the Kone River Basin (CentralVietnam) under climate change by applying the BTOPMC distributed hydrological model. Journalof Water and Climate change. Vol. 4. pp 1-11.Kendall, M.G., 1975. Rank correlation methods, 4th ed. Charles Griffin, London.Wang, G. Q., and Coauthors, 2013. Simulating the Impact of Climate Change onRunoff in a Typical River Catchment of the LoessPlateau, China. J. Hydrometeor, 14, 1553-1561.Wang, H., Chen, Y., Li, W., Deng, H., 2013:Runoff Responses to Climate change in Aridregion of Nortwestern China during 1960-2010.Chin. Gegra. Sci. vol. 23 No.3, pp.286-300.Bộ Tài nguyên và Môi trường, 2012. Kịch bản biến đổi khí hậu và nước biển dâng.ICCP, 2008. Climate change and water. ICCP technical paper VI. 200pp.

Testing the applicability of vacuum-encapsulated 40Ar/39Ar geochronology to pedogenic palygorskite and sepiolite

The difficulty of isolating intact, mineralogically pure pedogenic crystals from cemented soil is one of the most significant obstacles to quantifying rates of soil formation, geomorphic processes, and climate change in arid regions. We evaluate the applicability of vacuum encapsulated 40Ar/39Ar geochronology to pedogenic palygorskite and sepiolite extracted from the 4 to 5 Ma, extant Mormon Mesa petrocalcic soil-geomorphic surface of southern Nevada, and from the 780 ka to 2 Ma Jornada Experimental Range La Mesa soil-geomorphic surface near Las Cruces, New Mexico. Selective dissolution of cements using NaOAc and Tiron, accompanied by particle size fractionation, was used to isolate the pedogenic Mg-phyllosilicates. Scanning electron microscopy, inductively-coupled plasma spectrometry, X-ray diffraction, gas chromatograph mass spectrometry, and Ar isotope analysis were used to determine whether extraction impacted palygorskite/sepiolite suitability for 40Ar/39Ar geochronology. We found no adverse morphological or mineralogical effects, but meaningful ages could not be obtained due to small amounts of old, detrital phyllosilicates in the samples. While the potential of pedogenic palygorskite and/or sepiolite for geochronology now seems limited, results from this study may prove relevant for samples from other, non-pedogenic surface environments. It is hoped that this work will encourage further research towards successful 40Ar/39Ar geochronology of pedogenic phyllosilicates, as well as inform future geochemical or isotopic studies of individual pedogenic mineral species.

Runoff responses to climate change in arid region of northwestern China during 1960–2010

Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydroclimatic variables were studied by using both Mann-Kendall test and distributed-free cumulative sum (CUSUM) chart test. Results indicate that the mean annual air temperature increases significantly from 1960 to 2010. The annual precipitation exhibits an increasing trend, especially in the south slope of the Tianshan Mountains and the North Uygur Autonomous Region of Xinjiang in the study period. Step changes occur in 1988 in the mean annual air temperature time series and in 1991 in the precipitation time series. The runoff in different basins shows different trends, i.e., significantly increasing in the Kaidu River, the Aksu River and the Shule River, and decreasing in the Shiyang River. Correlation analysis reveals that the runoff in the North Xinjiang (i.e., the Weigan River, the Heihe River, and the Shiyang River) has a strong positive relationship with rainfall, while that in the south slope of the Tianshan Mountains, the middle section of the north slope of the Tianshan Mountains and the Shule River has a strong positive relationship with air temperature. The trends of runoff have strong negative correlations with glacier coverage and the proportion of glacier water in runoff. From the late 1980s, the climate has become warm and wet in the arid region of the northwestern China. The change in runoff is interacted with air temperature, precipitation and glacier coverage. The results show that streamflow in the arid region of the northwestern China is sensitive to climate change, which can be used as a reference for regional water resource assessment and management.

Water availability and successful lactation by bats as related to climate change in arid regions of western North America

1. Climate change in North America is happening at an accelerated rate, reducing availability of water resources for bats and other wildlife that require it for successful reproduction. 2. We test the water-needy lactation hypotheses directly by tracking the drinking habitats of individual lactating and non-reproductive female fringed myotis at an artificial water source located near a maternity roost. 3. We used a submerged passive integrative transponder (PIT) tag reader system designed to track fish to instead record numbers of water source visitations by tagged bats. 4. Of 24 PIT-tagged adult females, 16 (67%) were detected repeatedly by the plate antenna as they passed to drink between 18 July and 28 August 2006. 5. The total number of drinking passes by lactating females (n = 255) were significantly higher than those of non-reproductive adult females (n = 22). Overall, lactating females visited 13 times more often to drink water than did non-reproductive females. On average, lactating females visited six times more often per night. Drinking bouts occurred most frequently just after evening emergence and at dawn. 6. Drinking patterns of non-reproductive females correlated significantly with fluctuating ambient temperature and relative humidity recorded at the water source, whereas lactating females drank extensively regardless of ambient conditions. 7. We provide a mathematical model to predict the rate of decline in bat populations in the arid West in relation to climate change models for the region.

Environmental threats to salt lakes and the likely status of inland saline ecosystems in 2025

Salt lakes are geographically widespread, numerous and a significant part of the world's inland aquatic ecosystems. They are important natural assets with considerable aesthetic, cultural, economic, recreational, scientific, conservation and ecological values. Some features, notably the composition of the biota, uniquely distinguish them from other aquatic ecosystems. The paper reviews the nature of environmental impacts and their effects upon salt lakes. Its aims are two-fold: to draw attention to the extensive damage that salt lakes have now undergone, and to indicate the likely status of salt lakes in 2025. Salt lakes develop as the termini of inland drainage basins where hydrological inputs and outputs are balanced. These conditions occur in arid and semi-arid regions (approximately one-third of total world land area). Many human activities threaten or have already impacted salt lakes, especially surface inflow diversions, salinization and other catchment activities, mining, pollution, biological disturbances (e.g. introduction of exotic species), and anthropogenically-induced climatic and atmospheric changes. The effects of such activities are always adverse and include changes to the natural character of salt lakes, loss of biodiversity and fundamental limnological changes. The effects are geographically widespread, mostly irreversible, and degrade the values of salt lakes. Four salt lakes are discussed, namely the Aral Sea in central Asia, Mono Lake in California, USA, and Lake Eyre and Lake Cantara South, in Australia. By 2025, most natural salt lakes will have undergone some adverse change. Many permanent ones will have decreased in size and increased in salinity, and many unnatural saline water-bodies will have appeared. In certain regions, many seasonally-filled salt lakes are likely to be drier for longer periods. The extent to which episodically-filled salt lakes will change by 2025 will largely depend upon the nature of climate change in arid regions. Objective cost/benefit analyses of adversely affecting salt lakes are rare, and international bodies have not properly recognized salt lakes as important inland aquatic ecosystems. To redress this situation, there is a need to raise awareness of: (1) the values of salt lakes, (2) the nature of threats and impacts from human activities, and (3) their special management requirements. More effective management and conservation measures need to be implemented. Mono Lake provides an example of what can be achieved in the conservation of salt lakes. Its conservation was largely brought about by (1) the commitment of a non-governmental organization which recognized its non-economic values, (2) the freedom to express views, (3) a legal system which took account of non-economic values, and (4) a legislature which implemented judicial findings. The conservation of Mono Lake was difficult; the conservation of other salt lakes is likely to be even more difficult. Only international pressure from appropriate organizations will be effective for the conservation of many.