One century after its initial excavation, this article presents the first absolute chronology for the settlement of Karanis in Egypt. Radiocarbon dates from crops retrieved from settlement structures suggest that the site was inhabited beyond the middle of the fifth century AD, the time at which it was previously believed to have been abandoned. These dates add to the complex picture of population fluctuations and the remodelling and reuse of structures at Karanis. Two dates reach into the middle of the seventh century, placing the abandonment of the site in a period of political and environmental transition that changed the physical and social landscape of the Fayum region and beyond.

The United Nations Sustainable Development Goals aim to improve livelihoods and maintain functioning ecosystems, and include the provision of electricity and the prevention of desertification. We show that the pursuit of those two goals can lead to developments that put critical ecosystem functions at risk. Vultures are scavengers that provide sanitary ecosystem services, but their populations across Africa are declining due to poisoning, electrocution, and collision with power infrastructure. The extent to which the pursuit of sustainable development threatens vultures in Africa is unclear. We surveyed 227 km of powerlines in Ethiopia, which revealed bird mortality (0.15 vulture carcasses / km) at power infrastructure constructed under a National Electrification Programme to provide universal electricity access by 2025. We also interviewed 190 local pastoralists in 10 areas about livelihood challenges, which revealed that the bush Prosopis juliflora, which was originally introduced to prevent desertification but then invaded north-eastern Ethiopia, increased livestock predation and motivated the use of poison to control predators. Actions to increase universal access to electricity and to reduce desertification therefore have undesired side-effects that increase vulture mortality through electrocution and poisoning. To avoid negatively affecting local vulture populations and the services they provide, we urge governments to use infrastructure designs that minimise the risk of electrocution and assist pastoralists to protect their livestock and reduce the risk of poisoning to vultures and other wildlife.

In central Asia, Agriophyllum squarrosum is the first species to become established during natural succession on sand dunes. However, low germination percentages and thus poor stand establishment greatly inhibit the use of this key species in the stabilization of dunes. The aim of this review is to critically analyse published information on the seed biology of A. squarrosum with particular reference to identifying the factors limiting germination of seeds sown in the field. A conceptual model is used to illustrate the complexities of factors as well as the unknowns we found about the seed/seedling stage of the life cycle of this sand dune annual. A major result of this review is that we now know that high germination percentages can be obtained by storing freshly collected seeds dry at room temperatures for 2 to 3 months to allow dormancy break to occur via afterripening, and then storing them dry at low (e.g. 4–5°C) temperature to prevent them from entering secondary dormancy. Non-dormant seeds should be sown in the field in late spring when wind-blown sand will cover them, thus ensuring that they are in darkness, which promotes germination, at the time summer rains occur.

Desert plants are exposed to water shortage and often salinity, instantly after dormancy withdrawal. We studied the effects of aridity and salinity on germination and initial growth of Bassiaindica, B. iranica and B. prostrata. We hypothesized that: (1) all species would exhibit adaptations to water shortage immediately after germination, including rapid root growth and high seedling-survival rates; and (2) obligate halophytes benefit from positive effects of salinity on germination success and desiccation tolerance. After we germinated seeds in water or NaCl solutions, desiccated and rehydrated them, we found that all three species showed rapid germination and root elongation, as well as good germination success. However, salinity had a negative effect on the germination success of all three, with only B. indica germinating in 3% NaCl. Salinity had a positive effect on desiccation tolerance of B. indica seedlings, but had no significant effect on either B. prostrata or B. iranica. Thus the presence of salinity immediately after germination can protect halophyte seedlings from desiccation. To the best of our knowledge, survival of seedlings after periods of desiccation and rewetting with solutions of up to 3% NaCl has never been reported. Studying salinity tolerance in halophytes is important in a world exposed to expanding desertification.

Only green plants can convert the single carbon units of atmospheric carbon dioxide into the multi-carbon organic molecules on which all forms of life depend. Only green plants can provide the oxygen required by man and other aerobic organisms. In addition to his basic need for preformed organic molecules and oxygen, man also depends on plants to provide him, directly or indirectly, with an array of specific compounds such as vitamins and essential amino acids. Inadequate supplies of these may hinder growth and development or give rise to well defined deficiency diseases. At the present time information concerning the distribution and concentrations of such essential nutrients in plants is largely restricted to those plants that are already used as human foods. Nothing or virtually nothing is known about the chemical composition of approximately 250000 wild and little-used species. Amongst these there may be many that could provide us with cheap and plentiful new sources of essential nutrients that could be of enormous benefit to those suffering not only from full-blown deficiency diseases but also suffering sub-normal health due to partial deficiencies. The destruction of much of the world's wilderness areas has already deprived us of the opportunity to evaluate the contributions that a great many plant species might have made towards the elimination of deficiency diseases.

Many plants used as human foods contain compounds that are toxic to man. If intake is sufficiently high, these toxins may cause disease. Breeding programmes designed to eliminate toxins from crops species or reduce their concentrations to acceptable levels depend on genetic variability within the species or the possibility of producing hybrids with the desired characteristics. The motor neurone disease, lathyrism, which affects populations in the Indian sub-continent, Africa and China is caused by a toxin in the seeds of Lathyrus sativus. Surveys of cultivated plant populations have shown great variability in toxin levels and such genetic differences make it possible to select and breed toxin-low varieties. The existence of toxin-free species within the same genus has led to research aimed at producing toxin-free hybrids suitable for agricultural use. Approaches, designed to reduce or eliminate diet-related diseases, depend on the maintenance of the greatest possible diversity among both wild and cultivated plant populations. Such diversity is under threat.

Some 250 plant species are used as sources of drugs in western medicine. Most of these drugs are obtained from plants whose therapeutic value was recognized long before the compounds were isolated. In the developing countries of the world, it is estimated that 25000 plant species may be used in medicinal preparations. Few of these plants have been studied systematically to determine whether their reputations are justified and if so, the nature of the drugs they contain. If only 0.1 % were to yield useful drugs, they could make a major contribution to human health and welfare. The plants and the indigenous populations who understand their uses are both disappearing and it is a matter of great regret that much that could be of value has been and will be lost.

Are scientific or nonscientific factors most influential in initiating international cooperation on newly emerging transboundary environmental problems in the Asia and Pacific region? In a case study of long-range atmospheric transport of dust, which is linked to desertification in China and Mongolia, the relative influence of scientific versus nonscientific factors in promoting cooperation in the region is analyzed. The study examines two dimensions of the problem—Northeast Asia and North America—and demonstrates that similar to the distance-dependence of the problem (i.e., dust concentrations decrease the greater the distance from the sources), cooperation follows a parallel relationship (i.e., motivation to cooperate decreases the greater the distance from the sources). Scientific cooperation in Northeast Asia is being institutionalized, but North America has not joined this effort. A synergy between factors must be invoked to explain this situation. In both cases, obvious and often dramatic negative impacts of massive dust storms are an enabling factor allowing more subtle science-related factors to come to the fore.

In the semi-arid rangelands of the Oshana ecosystem in Northern Namibia, there are general concerns that artificial water points for domestic use contribute to the processes that lead to desertification. The processes begin in piospheres of artificial water points. Among the processes suggested to correlate with radial distance and age of water points are loss of perennial grass species, an increase in annuals, and general loss of herbaceous species richness, herbaceous biomass and grass cover, as well as an increase in forb cover and in bare ground and litter cover. Radial distance and age of artificial water points impacts were compared using these indicators with benchmarks in saline grassland and mopane landscape at the end of the wet season. Radial distance influenced herbaceous species richness, grass cover and bare ground, while the variability of the perennial:annual grass ratio, herbaceous biomass, forb and litter cover were attributed to differences between landscape types. Age of water points influenced only herbaceous species richness, while forb cover was associated more with water points than benchmarks. Forb cover was sporadic in relation to age of water points. In the Oshana ecosystem, therefore, radial-grazing distance could not be used to explain changes in the perennial:annual grass ratio. Many of the changes were explained by differences between landscape types. The mopane landscape was more vulnerable to degradation induced by artificial water points than the grassland landscape. The implication is that, in the future, greater care should be taken to space water points in the mopane landscape.

There is increasing international concern about the environmental impacts of refugees on host areas, with governments calling for compensation for environmental damage, particularly concerning the loss of woodland resources as a result of demand for wood for fuel. In addition to an obvious increase in the population of host areas, concern about refugees' woodfuel-use centres on the notion that they are 'exceptional resource degraders'. Since they view their stay as temporary, it is argued, they therefore do not have any incentive to use resources in a way that is sustainable in the long term. This study examined refugee migration to the middle valley of the Senegal River, and compared woodfuel use by refugee and local populations. Drawing on a household survey and direct measurement of woodfuel use, little or no evidence is found to support the expectation that refugees use more wood for fuel than local people, or that they are more destructive in their collection or use of wood. This is important since it suggests that policy measures developed to reduce what is perceived as excess demand by refugees, notably through the introduction of fuel-efficient stoves, are unlikely to be successful. Reforestation schemes have been relatively unsuccessful in addressing supply or demand for wood.

Field research and predictive modelling of global warming and desertification by environmental scientists in the Mediterranean has concentrated on the short term. In this paper, it is argued that collaboration between the historical sciences, especially archaeology, and the environmental sciences can provide a longer-term perspective on desertification in the Mediterranean. Such collaboration has taken place recently in the Vera basin (Almería, south-east Spain), with the financial support of the European Union. Details of the archaeological and historical sequences of occupation in the basin are given, before presenting the main trends in demography, settlement and political systems from 4000 BC until the present day. This is followed by details of the long-term record of degradation in the Vera basin. The paper concludes by using the long-term record to propose recommendations for the future management of this landscape.

The problem of land degradation is not new, but never before has it been so widespread or affected the lives of so many people. The need for a global assessment of land degradation was highlighted by the United Nations Conference on the Human Environment in 1972. Since then, several attempts have been made to develop methodologies that will allow for systematic assessment and monitoring of global land degradation. Systematic work started in 1975, when FAO and United Nations Environment Programme (UNEP) collaborated in a study to develop a provisional method for soil degradation. This method was tested, and maps on a scale of 1:5,000,000 were produced for North Africa and the Near East. However, the method proved difficult to apply accurately, so this project was followed by another where the method was revised and refined in an effort to assess and map desertification. Again, problems were encountered because of the complexity of the subject and the lack of usable reliable data. More recently, ISRIC, using a simplified methodology and the assistance of some 250 scientists from around the world, has produced a world map of human induced soil degradation at a scale of approximately 1:10,000,000. Meanwhile, interest has been growing in the problem of nutrient depletion in developing countries and a study has been completed of N, P and K balances in the soils of 38 African countries. Although we still do not have an accurate assessment of global land degradation and no systematic monitoring is yet in place, these innovative studies have provided us with a sound basis for future work and have identified many of the practical problems of measuring land degradation, data collection and analysis that will have to be overcome before more accurate assessment and monitoring can be achieved.