Barrage debate

OPINION LETTERS Barrage debate From Gerry Wolff, Desertec-UK It is true that decarbonising the world’s economies will require some tough choices, but perhaps not quite as tough as Fred Pearce suggests in his article on the implications of a Severn barrage (18 April, p 32). A report published by Friends of the Earth Cymru in 2007 quotes evidence that tidal lagoons in the Severn estuary could produce more electricity than the proposed barrage, and with less harm to wildlife. There are other methods of power generation, too, such as solar power. Less than 1 per cent of the world’s deserts could produce as much electricity as the world is now using; less than 3 per cent could produce the amount of electricity that is equivalent to the world’s total energy needs. It should be possible to protect sensitive areas of desert. New developments in high-voltage direct-current transmission lines mean that long-distance power cables can be laid underground or underwater without costing much more than

overhead lines. They have the advantage of causing less visual intrusion. To this end, the investment company Imera has recently announced a €4.4 billion plan to begin creating a pan-European transmission grid made up entirely of submarine cables. Menai Bridge, Anglesey, UK From Roger Freeman While I am all for looking after the birds, I am sure that they have survived far worse perturbations

of habitat during the last 60 million years than would be caused by a Severn barrage. They will adapt, as ever. Portbury, Somerset, UK

Enigma Number 1544 Spanish squares RICHARD ENGLAND Cero, uno and nueve are the Spanish words for 0, 1 and 9, so it is appropriate that I can make the following statement: CERO, UNO and NUEVE are perfect squares. In this statement digits have been consistently replaced by capital letters, different letters being used for different digits. Please send in the numerical value of the square root of (CERO × UNO × NUEVE). WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 10 June. The Editor’s decision is final. Please send entries to Enigma 1544, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to [email protected] (please include your postal address). Answer to 1538 Six factors: The “third number” common to both sums was 93 The winner Martin Kipps of Wokingham, Berkshire, UK

24 | NewScientist | 9 May 2009

Save the Red List From Matthew Godfrey, North Carolina Wildlife Resources Commission, Beaufort, North Carolina; Brendan Godley, Center for Ecology and Conservation, University of Exeter, UK; Nicholas Mrosovsky, Department of Ecology and Evolutionary Biology, University of Toronto, Canada; Jeffrey Seminoff, Marine Turtle Research Program, US National Marine Fisheries Service; Kartik Shanker, Centre for Ecological Sciences, Indian Institute of Science, Bangalore; and Grahame Webb, Wildlife Management International, Sanderson, Northern Territories, Australia In their response to your article on the IUCN Red List, Jeff McNeely and others (4 April, p 20) fail to address specific criticisms of the list that are raised in the special issue of Endangered Species Research that sparked your article. One of these criticisms concerns the threat to the Red List’s credibility when it identifies as endangered some species that are unlikely to disappear. For example, McNeely and his co-writers admit that there are millions of green turtles, yet stand by the “endangered” listing for the species, disregarding a wealth of literature to the contrary, such as the report by Milani Chaloupka and others published last year in Global Ecology and Biogeography (vol 17, p 297). The Red List undoubtedly contributes significantly to the conservation of global biodiversity. This makes it all the more important to maintain the scientific credibility of the IUCN and of the Red List’s front-line market product: identification of those species threatened with global extinction.

Showery outlook From John Mattocks Fred Pearce’s excellent article “Keep the planet’s heart

pumping” (4 April, p 6), which described how coastal rainforests could cause rainfall to travel inland, stirred a memory from my youth in eastern England. After the second world war, huge coniferous forests were planted in the Breckland area of Norfolk and Suffolk, replacing what had been sparse bracken, heather and gorse. Local folklore claimed that this forestation resulted in a measurable increase in rainfall downwind of the area, affecting prime agricultural land which previously had typically only 30 centimetres of rain per year. I have never seen scientific substantiation of this, although historical and meteorological records verifying it would support Victor Gorshkov and Anastassia Makarieva’s theory. How good it is to hear a theory that, for once, could enable us to change our habitat for the better. Alcester, Warwickshire, UK From Kris Ericksen While the theory described by Fred Pearce may be a “major driver of atmospheric circulation on Earth”, the pressure drop caused when water vapour turns to water may also be a significant factor in the “billowing shower curtain” problem that has in the past exercised Feedback. David Schmidt’s “vortex model” (28 July 2001) does not account for the person in the shower breaking up the vortex, nor does it explain why a lowvolume hot shower creates more billowing than a high-volume cold shower. Putting warm water into a