Aviation and global climate change in the 21st century

Aviation emissions contribute to the radiative forcing (RF) of climate. Of importance are emissions of carbon dioxide (CO₂), nitrogen oxides (NO_x), aerosols and their precursors (soot and sulphate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness. The recent Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) quantified aviation's RF contribution for 2005 based upon 2000 operations data. Aviation has grown strongly over the past years, despite world-changing events in the early 2000s; the average annual passenger traffic growth rate was 5.3% yr^?1 between 2000 and 2007, resulting in an increase of passenger traffic of 38%. Presented here are updated values of aviation RF for 2005 based upon new operations data that show an increase in traffic of 22.5%, fuel use of 8.4% and total aviation RF of 14% (excluding induced-cirrus enhancement) over the period 2000–2005. The lack of physical process models and adequate observational data for aviation-induced cirrus effects limit confidence in quantifying their RF contribution. Total aviation RF (excluding induced cirrus) in 2005 was ～55 mW m^?2 (23–87 mW m^?2, 90% likelihood range), which was 3.5% (range 1.3–10%, 90% likelihood range) of total anthropogenic forcing. Including estimates for aviation-induced cirrus RF increases the total aviation RF in 2005–78 mW m^?2 (38–139 mW m^?2, 90% likelihood range), which represents 4.9% of total anthropogenic forcing (2–14%, 90% likelihood range). Future scenarios of aviation emissions for 2050 that are consistent with IPCC SRES A1 and B2 scenario assumptions have been presented that show an increase of fuel usage by factors of 2.7–3.9 over 2000. Simplified calculations of total aviation RF in 2050 indicate increases by factors of 3.0–4.0 over the 2000 value, representing 4–4.7% of total RF (excluding induced cirrus). An examination of a range of future technological options shows that substantive reductions in aviation fuel usage are possible only with the introduction of radical technologies. Incorporation of aviation into an emissions trading system offers the potential for overall (i.e., beyond the aviation sector) CO₂ emissions reductions. Proposals exist for introduction of such a system at a European level, but no agreement has been reached at a global level.     

Aging and improving reproductive success in horses: declining residual reproductive value or just older and wiser?

In many mammalian species, female success in raising offspring improves as they age. The residual reproductive value hypothesis predicts that each individual offspring will be more valuable to the mother as she ages because there is less conflict between the current and potential future offspring. Therefore, as mothers age, their investment into individual offspring should increase. Empirical evidence for an influence of declining residual reproductive value on maternal investment is unconvincing. Older mothers may not invest more, but may be more successful due to greater experience, allowing them to target their investment more appropriately (targeted reproductive effort hypothesis). Most studies do not preclude either hypothesis. Mare age significantly influenced maternal investment in feral horses living on the North Island of New Zealand. Older mares, that were more successful at raising foals, were more protective for the first 20 days of life, but less diligent thereafter. Total maternal input by older mothers did not seem to be any greater, but was better targeted at the most critical period for foal survival and a similar pattern was observed in mares that had lost a foal in the previous year. In addition, older mothers were more likely to foal in consecutive years, supporting the hypothesis that they are investing less than younger mares in individual offspring. Therefore, older mothers seem to become more successful by targeting their investment better due to experience, not by investing more in their offspring. Received: 22 September 1999 / Received in revised form: 30 October 1999 / Accepted: 6 November 1999     

Seasonal breeding aggregations in low-density populations of the bathyal echinoid Stylocidaris lineata

Reproduction of bathyal cidaroid sea urchins was studied between 1985 and 1991 with the aid of a manned submersible in the northern Bahamas. During May 1988 and February 1990, discrete, single-species aggregations of Stylocidaris lineata containing 2 to 6 individuals were observed between 510 and 640 m depths. Reproductive conditions of isolated and aggregated individuals were determined histologically. In February, all individuals, regardless of their spatial distribution, contained developing gametes. During the May spawning season, most isolated individuals contained spent gonads with only relict gametes, whereas individuals in discrete aggregations mostly contained ripe gonads with mature or nearly-mature gametes. Aggregations were not observed during the autumn months, when gonads were spent or immature. These data suggest that bathyal cidaroids aggregate for reproduction. An in situ survey during May indicated that pairs of S. lineata are more common than larger clumps, but no more so than predicted by chance. Homosexual and heterosexual pairs occur at the relative frequencies predicted on the basis of sex ratio. We evaluated the need for reproductive aggregation by applying Denny's (1988) model that predicts downstream sperm concentration in a turbulent boundary layer. Flow parameters were measured with dye injected from the submersible, sperm-release rate was estimated in the laboratory, and the relationship between fertilization success and sperm concentration was determined in a laboratory dilution-experiment. The model predicted that, on smooth sandy bottoms at bathyal depths, sperm concentration should remain high enough to fertilize at least some eggs several meters directly downstream from a spawning male. Aggregation may facilitate spawning synchrony, increase gamete encounter probabilities, or cause gametes to be retained at high concentrations near the adults long enough for fertilization to occur.     

Chemical signals in bumble bee foraging

Summary Foraging bumblebees (Bombus vosnesenskii) deposit a substance on rewarding flowers which assists in discrimination between rewarding and nonrewarding flowers in a controlled laboratory environment. Discrimination occurs while the bee is on a flower; workers probe rewarding flowers as well as empty ones that have rewarded in the recent past, but they do not probe flowers that have had no reward. Recognition is not the result of honey contamination left on the flower by the bee during feeding. The deposit is only slightly soluble in water or ethyl alcohol but is very soluble in pentane.     

Manganese nodules and marine technology

This article examines the problems and prospects of manganese nodule mining. The technological requirements for the exploitation of nodule deposits are considered, superimposed on an interdisciplinary policy-oriented approach. The technological dimension is emphasized because its crucial importance is often underrated when deep ocean mining is assessed. This dimension cannot be divorced from the interactions between economics, international law and oceanography. The technological problems and opportunities of nodule mining are diverse. Provided delays at the UN and economic uncertainties do not channel some of the interest into land-based alternatives, this could be an important area of future technical development.     

Book reviews

Land and Leisure — Concepts and Methods in Outdoor Recreation

Second Edition — edited by C. S. Von Doren, G. B. Priddle and J. E. Lewis.

Methuen & Co., £5.95. 1979.

Countryside Planning — The First Three Decades, 1945–76

Andrew W. Gilg.

Methuen & Co. £3.50. 1979.

Social Problems and the City

D. T. Herbert and D. M. Smith

Oxford University Press. £8.50. 271 pp.

Slum Housing and Residential Renewal — The Case of Urban Britain

D. A. Kirby

Topics in Applied Geography Series. Longmans. £2.95. 1979.

From Blacksmiths to White Elephants: Benwell's Changing Shops

Benwell Community Project Final Report, Series No. 7, Newcastle upon Tyne 1979. 72 pp. 80p.

The Debate on Urban Policy — Decentralisation versus Improvement

Robert Coursey

Retailing and Planning Associates 1977. 93 pp.

Urban Deprivation and Government Initiatives

Paul Lawless

Faber. £8.95 (hard‐back), 251 pp.

A Guide to Historic Buildings Law Fourth Edition

Peace, D., and Purdy, I. M.

Cambridgeshire County Council, County Planning Department, 1979.

98 pp. (paperback), £5.35 post paid.

Research and Intelligence

Papers delivered at the Annual Conference 1978, Inlogov University of Birmingham Edited by E. M. Davies

£4.30. 257 pp.

Geography and the Urban Environment : Progress in Research and Applications

Vol. II. Edited by D. T. Herbert, R. J. Johnston.

Wiley, London. 308 pp.

Facts about the New Towns : A Socio‐Economic Digest

A. G. Champion, K. Clegg and R. L. Davies

R.P.A., Corbridge, 1978.

Physical Planning in the Member States of the E.E.C.

C. Wood and N. Lee, Occasional Paper No. 2.

Department of Town and Country Planning, University of Manchester, 1978. 59pp.     

Book reviews

ENFORCEMENT AND STOP NOTICES

Felix Bourne

Sweet and Maxwell, London 1986

SMALL FACTORIES AND ECONOMIC DEVELOPMENT

By Martin Perry

(Aldershot; Gower, 1986, pp.xvi + 229) £22.50

WHATEVER HAPPENED TO PLANNING?

Peter Ambrose, 1986

Methuen, London and New York, 288pp, £8.95.     

Application of side-scan sonar in marine biology

Side-scan sonar provides an acoustic picture of the sea floor which can be viewed as if it were an unrectified, aerial photograph. Resolution is such that both sediment and faunal facies boundaries can be mapped on the basis of their varying acoustical response. Tracks left by commercial fishery dredges are often clearly visible on the bottom because of the contrast in bottom roughness between the dredged path and the surrounding, undisturbed sediment. The boards of otter trawls leave true furrows in the bottom, which can frequently be followed on side-scan imagery. Terraces built of dead roots of Posidonia oceanica L. plus entrapped sediment could be delineated over a large area of the North Adriatic Sea. Reefs and areas of secondary hard bottom — of interest to biologists and geologists alike — have been effectively mapped using side-scan sonar.