Current Projections (current + projection)

Distribution by Scientific Domains

Selected Abstracts

A First Estimate of Ground Water Ages for the Deep Aquifer of the Kathmandu Basin, Nepal, Using the Radioisotope Chlorine-36

GROUND WATER, Issue 3 2001
Richard G. Cresswell
The Kathmandu Basin in Nepal contains up to 550 m of Pliocene-Quaternary fluvio-lacustrine sediments which have formed a dual aquifer system. The unconfined sand and gravel aquifer is separated by a clay aquitard, up to 200 m thick, from the deeper, confined aquifer, comprised of Pliocene sand and gravel beds, intercalated with clay, peat, and lignite. The confined aquifer currently provides an important water supply to the central urban area but there are increasing concerns about its sus-tainability due to overexploitation. A limited number of determinations of the radioisotope 36Cl have been made on bore waters in the basin, allowing us to postulate on the age of ground water in the deeper, confined aquifer. Ground water evolution scenarios based on radioisotope decay, gradual dissolution of formational salts as the ground waters move downgradient, and flow velocity estimations produce comparable ground water ages for the deep waters, ranging from 200,000 to 400,000 years. From these ages, we deduce a mean ground water flow velocity of only 45 mm/year from recharge in the northeast to the main extraction region 15 km to the southwest. We thus estimate current recharge at about 5 to 15 mm/year, contributing 40,000 to 1.2 million m3/year to the ground water system. Current ground water extraction is estimated to be 20 times this amount. The low specific discharge confirms that the resource is being mined, and, based on current projections, reserves will be used up within 100 years. [source]

How important is climate?

Effects of warming, fish on phytoplankton in shallow lake microcosms, nutrient addition
Summary 1Climate is changing. Predictions are for at least a 3 C rise in mean temperature in northern Europe over the next century. Existing severe impacts of nutrients and inappropriate fish stocking in freshwater systems remain. 2Effects of warming by 3 C above ambient, nutrient addition and the presence or absence of sticklebacks Gasterosteus aculeatus were studied in experimental microcosms dominated by submerged plants, mimicking shallow lake ecosystems. 3Warming had considerably smaller effects on the phytoplankton community than did fish and nutrients. It had very minor effects on chlorophyll a and total phytoplankton biovolume. However, it significantly decreased the biovolumes of Cryptophyceae (a major component in the controls) and Dinophyceae. Contrary to expectation, warming did not increase the abundance of blue-green algae (cyanophytes). Warming decreased the abundances of Cryptomonas erosa (Cryptophyceae) and Oocystis pusilla (Chlorophycota) and increased those of two other green algae, Tetraedron minimum and Micractinium pusillum. It had no effect on a further 17 species that were predominant in a community of about 90 species. 4Fish and nutrients, either together or separately, generally increased the crops of most of the 21 abundant species and of the algal groups. Exceptions were for diatoms and chrysophytes, which were very minor components of the communities. Fish, but neither nutrients nor warming, increased the number of species of phytoplankton detected. This was probably through removal of zooplankton grazers, and parallels terrestrial studies where the presence of top predators, by controlling herbivores, leads to increased plant diversity. 5There was no particular pattern in the taxonomy or biological characteristics of those species affected by the treatments. In particular, there was no link between organism size (a surrogate for many important biological features of phytoplankton species) and the effects of warming, nutrient addition or presence or absence of fish. However, all species were relatively small and potentially vulnerable to grazing. 6Synthesis and applications. The results suggest that fears of an increasing abundance of cyanophytes with current projections of global warming may be unrealized, at least in shallow unstratified lakes still dominated by macrophytes. However, they emphasize that eutrophication and fish manipulations remain very important impact factors that determine the abundance of phytoplankton and subsequent problems caused by large growths. [source]

Alan Greenspan on the Economic Implications of Population Aging

Article first published online: 15 DEC 200
At the 2004 annual symposium of central bank leaders sponsored by the Federal Reserve Bank of Kansas City at Jackson Hole, Wyoming, Alan Greenspan, Chairman of the US Federal Reserve Board, devoted his opening remarks on 27 August to a discussion of the economic implications of population aging. The full text of his remarks is reproduced below. Greenspan's high prestige and great influence on US economic policy lend special interest to his views on this much-discussed subject (see also the next Documents item in this issue). He outlines the coming demographic shift in the United States in language that is characteristically cautious and qualified. (The elderly dependency ratio will "almost certainly" rise as the baby boom generation retires, Greenspan says, although elsewhere he terms the process, more accurately, inexorable.) The main factor responsible for population aging he identifies as the decline of fertility. Immigration is an antidote, but, to be effective, its size would have to be much larger than is envisaged in current projections. Greenspan's assessment of the economic consequences of the changing age structure highlights the prospect of a deteriorating fiscal situation in the United States: chronic deficits in the Social Security program over the long haul, assuming that existing commitments for benefits per retiree are met, and even greater difficulties for the health care system for the elderly,Medicare,in which the effects of increasing numbers in old age are amplified by advances in medical technology and the bias inherent in the current system of subsidized third-party payments. The sober outline of policy choices imposed by population aging,difficult in the United States, but less so, Greenspan notes, than in Europe and Japan,underlies the need for counteracting the declining growth of the population of labor force age through greater labor force participation and later retirement. Beyond that, growth of output per worker can provide the key "that would enable future retirees to maintain their expected standard of living without unduly burdening future workers." This requires continuation of policies that enhance productivity, such as deregulation and globalization, and greater investment. In turn, the latter presupposes greater domestic saving, both personal and by the government, as the United States cannot "continue indefinitely to borrow saving from abroad." Demographic aging requires a new balance between workers and retirees. Curbing benefits once bestowed is difficult: only benefits that can be delivered should be promised. Public programs should be recalibrated, providing incentives for individuals to adjust to the inevitable consequences of an aging society. [source]

Bioengineering nitrogen acquisition in rice: can novel initiatives in rice genomics and physiology contribute to global food security?

BIOESSAYS, Issue 6 2004
Dev T. Britto
Rice is the most important crop species on earth, providing staple food for 70% of the world's human population. Over the past four decades, successes in classical breeding, fertilization, pest control, irrigation and expansion of arable land have massively increased global rice production, enabling crop scientists and farmers to stave off anticipated famines. If current projections for human population growth are correct, however, present rice yields will be insufficient within a few years. Rice yields will have to increase by an estimated 60% in the next 30 years, or global food security will be in danger. The classical methods of previous green revolutions alone will probably not be able to meet this challenge, without being coupled to recombinant DNA technology. Here, we focus on the promise of these modern technologies in the area of nitrogen acquisition in rice, recognizing that nitrogen deficiency compromises the realization of rice yield potential in the field more than any other single factor. We summarize rice-specific advances in four key areas of research: (1) nitrogen fixation, (2) primary nitrogen acquisition, (3) manipulations of internal nitrogen metabolism, and (4) interactions between nitrogen and photosynthesis. We develop a model for future plant breeding possibilities, pointing out the importance of coming to terms with the complex interactions among the physiological components under manipulation, in the context of ensuring proper targeting of intellectual and financial resources in this crucial area of research. BioEssays 26:683,692, 2004. 2004 Wiley Periodicals, Inc. [source]