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Stay of execution for Kenya's forests Thursday, 15 March, 2001, BBC

The land on Mount Kenya's slopes is very fertile A High Court in western Kenya has granted an injunction to prevent the government from handing over protected forest lands to individual Kenyans.

The court in Eldoret made the order after being petitioned by a small human rights group.

Environmental campaigners have condemned government plans to take over 14 forests on the slopes of Mount Kenya - an area of more than 160,000 acres.

They say the area, which represents one tenth of all Kenya's forests, has already been devastated by illegal logging, and any further disruption will have a serious impact on a vital water-catchment area.

Squatters

Correspondents say these groups fear the government may try to use the land to buy support in the run-up to elections next year.

Tthe government says it is simply trying to tidy up the forest boundaries, and that much of the land is already being lived on.

Centre For Human Rights and Democracy Lawyer Ken Wafula described some of the wealthy individuals on the land as "Pajero squatters".

He said he was pleasantly surprised at the court decision - but he believed the struggle was not over.

He said it was a human rights issue - for many Kenyans around Mount Kenya could suffer and even starve if the handover of forest went ahead.

The accused NS 3 Mar 2001
Is the biotech industry trying to silence one of its outspoken critics?

SUPPORTERS of the biotech industry have accused an American scientist of misconduct after she testified to the New Zealand government that a genetically modified bacterium could wreak havoc if released. The New Zealand Life Sciences Network, an association of pro-GM scientists and organisations, says the view expressed by Elaine Ingham, a soil biologist at Oregon State University in Corvallis, was exaggerated and irresponsible. It has asked her university to discipline her. But Ingham stands by her comments and says the complaints are an attempt to silence her. "They're trying to cause trouble with my university and get me fired," Ingham told New Scientist. The controversy began on 1 February, when lngliani testified before New Zealand's Royal Commission on Genetic Modification, which will determine how to regulate GM organisms. lngham claimed that a GM version of a common soil bacterium called Klebsiella planticola could spread and devastate plants if released into the wild. Other researchers had previously modi,fied tile bacterium to produce alcohol from organic waste. But Ingham says that when she plit it in soil with wheat plants, all of the plants died within a week. "We would lose terrestrial plants ... this is an organism that is potentially lethal to the continued survival of human beings," she told the coiniiiission. Sile added that the US Environmental Protection Agency (EPA) revoked its approval for field tests using the organism once she had told them about her research in 1999.

But last week the New Zealand Life Sciences Network accused Ingham of "presenting inaccurate, careless and exaggerated inforniation" and "generating speculative doomsday scenarios that are not scientifically supportable". They say that her study doesn't even show that the bacteria would survive in the wild, much less kill massive numbers of pIants. What's more, the network says that contrary to Ingliam's claims, the EPA was never asked to consider the organism for field trials. The EPA has not commented on the dispute. But an e-mail to the network froni Janet Anderson, director of the EPA's bio-pesticides division, says "there is no record of a review and/or clearance to field test" the organism. Ingham says EPA officials had told her that the organism was approved for field tests, but says she has few details. It's also not clear whether the organism, first engineered by the Institute for Molecular Biology in Julich, Germany, is still in use.

Crtics say the industry is trying to silence her. The Provost of Oregon State University, T. P. White, says the school is investigating the complaint. Kurt Kieiner

Blown away
More radioactive material has gone missing off the coast of Scotland NS 3 Mar 2001

An Experiment designed to discover ttie fate of 28 totiiies of depleted uranium in shells fired itito tile sea off south-west Scotland lias gone disastrotusly wrotig. Military scientists have lost DU samples they placed on the seabed to see if the original sliells might have corroded leaching the dense, radioactive imetal into the sea. l,ast year, the British government's Defence Evaluatiori and Research Agency (DERA) put 90 simall cylinders of DU on the seabed of the Solway Firth. But last month they went missing after severe storms buffeted the region.

Ttie experiment was a reslpolne to I)ublic coticeril about the datigers of 6900 DU shells fired itito the Firth from tanks on the Dundrennati army range near Kirkcudbright over tile past 20 years. despite searches, scientists found no trace of these shells, tliough a fistierman dredged one up by accident in 1997.

To try and find out what had happened to the shells, DERA intended to retrieve its DU samples for analysis from time to time. But when divers tried to do this in early February, the samples had gone. The seabed rig holding 66 of the cylinders was badly daniaged, while another 24 cylinders that had been buried in the silt could not be traced.

Divers from the Fasiane nuclear submarine base on the Clyde are due to start hunting for the missing DU samples next week. The samples are "a negligible addition" to the DU shells already on the seabed, a DERA spokeswoman says. DERA scientists believe DU in the sea forms an insoluble sludge of hydrated uranium oxide which is dispersed by underwater currents. But the Scottish Environment Protection Agency points out that without the evidence it's impossible to be sure. "At present we are unable to provide proper public reassurance," says the agency's chairman, Ken Collins. Environmentalists fear that the shells could break up and be washed ashore on beaches in storms. Rob Edwards, Edinburgh

Logging ban backfires

China's hunger for wood is squeezing the life out of Asian forests NS 3 Mar 2001

A RECENT logging ban in China is having an unexpected knock-on effect. 'ro meet its insatiable hunger for timber, the country has become the world's second. largest importer of wood, a development that could sound the death knell for the forests of South-East Asia.

China banned logging in virgin forests after massive floods on the Yangtze in 1998. Scientists convinced the government that logging in the headwaters of the river, the third largest in the world, contributed to flash floods that burst the river's banks and caused billions of dollars' worth of damage.

But government figures obtained last month by the China office of the World Wide Fund for Nature reveal that China has now come from nowhere to being a bigger importer of timber than Japan. Over the past 30 years, Japan has systematically destroyed the rainforests of the Philippines and much of Borneo. Now environmentalists fear China will chop down the rest.

"Before the logging ban, China imported around 4 million cubic metres of timber a year," says Zhu Chiinquang, WWF's forest programmes officer in Beijing. "in 1999, the first year after the ban, the figure rose to 10 million and we have just heard that the figure for 2000 was approaching 15 million."

China is buying hardwoods from the rainforests of Malaysia, Indonesia, Papua New Guinea and the African state of Gabon (see Graphic), and softwoods such as spruce and fir from Siberia. lt is now the world's second biggest timber importer, after the US. "Chinese timber companies are setting up abroad," says Zhu. "They are renting large areas of forests in Sabah, Borneo, and setting up pulp mills. 'They are even investing in New Zealand and Brazil."

The official import statistics may be an underestimate, says Anatoly Sclividenko, Russian forestry specialist at the International Institute for Applied Systenis Analysis in Laxenburg, Austria. "The logging ban in China has created a niajor black market for illegal harvesting in thee Siberia forests of Irkutsk and Tomsk," lie told New Scientist. There are also reports of a cross-border timber trade with China's southern neiglibours, including Burma.

The ban has proved very effective. "until two years ago, outsiders were banned from many roads in northern Sichuan because they were used exclusively for logging vehicles," says a local forestry official. Apart froni a few bicycles and buses, the roads are now empty. Fred Pearce, Beijing

Seconds out, round two
Frankenfoods are on the ropes but biotech is due for a comeback NS 28 Oct 2000

IF YOU live in Europe it is easy to believe that genetically modified crops are finished. Skilful media campaigns by activist groups have made these "frankenfoods" about as popular as nuclear power stations. Supermarkets and restaurants proudly announce themselves "GM free" and protestors trample fields of test plantings of modified crops with impunity. In North America too, despite earlier acceptance, a backlash is under way. With GM crops on the ropes, it seems a strange time to announce that they could have a really bright long-term future. But if you read the signs, honestly assess the world's future food needs, and look at the safer, greener, genetically modified crops we could produce, then the conclusion is exactly that. Future GM crops won't look the same as the first set of products, which were designed to create colossal monocultures protected by massive use of herbicides. And they might not appear at all unless scientists engage vigorously in the debate over their future and governments listen to the right advice. One sign of a more positive future for GM crops comes this week in a report from Britain's Advisory Committee on Releases to the Environment (ACRE), a committee of 13 independent experts who advise the government on the release and marketing of genetically modified organisms (see p 4). The report focuses on ways that GM plants could be made safer. It lists techniques that would greatly reduce the risks of, for example, pollen from stands of modified crops spreading to other fields. Plants can be engineered not to produce pollen at all, or to produce pollen that is incompatible with other unmodified plants. Even more important are techniques described in the report that are still in development. Add tcr those the many other possibilities appearing as our knowledge of plant genomes deepens and you have the potential for a quite different GM revolution. The genetically engineered crops that the world has come to hate were created by introducing foreign genes that either boost herbicide resistance or add protection from pests. Much more subtle interventions now look possible. Among them are ways of changing the regulation of the genes that plants already possess, to create plants that have larger leaves, flower earlier, and produce deeper roots or shorter stems. This may not sound like much, but the potential benefits are huge. Larger leaves can shade out weeds. Small adjustments in flowering time may make it easier to grow more than one crop a year. Deeper roots combat drought. And shorter stems leave more energy to boost seed harvests. These are the kinds of changes that conventional breeders have been making for thousands of years. Knowledge of genes and their control do the same-but much faster. More dramatic changes might be possible by har nessing the extraordinary powers of apomixis (see p 5). Many plants reproduce asexually, generating seed but no pollen. By transfer ing suitable controlling genes to crop plants, it should be possible to make them produce seeds that are genetically identical to the parent. This would be a boon to farmers, as it would allow them to gather seeds from their own crops and replant them year after year. Currently, this cannot be sustained for long, as top-quality genetic strains interbreed and gradually lose their vigour. Apomixis could be great news for farmers who can't afford premium commercial seeds. But wouldn't the power of apomixis run into opposition from the big agricultural companies, who now sell seed to farmers every year. Not necessarily. Apomixis has the potential to speed up the process by which desirable characteristics are fixed, making it much easier to create more seed varieties, each adapted to local conditions. That could be a big help in poorer countries with small and diverse farming systems. But it is only likely to happen if governments make sure that research on apomixis is well supported, and the rights to use the techniques are freely available. Which brings us back to the question: how can we make sure that we get the kind of biotechnology we want? Scientists must join in debate over what is best, rather than unquestioningly supporting research projects set by their employers. And goverrunents must seek out the right scientific advice and have the courage to act on it. Next week will see the publication of a vast govemment report on Britain's BSE fiasco. We expect it to criticise the way the goverrunent commissions and acts on scientific advice. With any luck, it's criticism that will change the kinds of science that shape society. El

Make them safe NS 28 Oct 2000 4
Genetically modified crops are riskier than they should be

BIOTECH companies could do a lot more to ensure the safety of genetically modified crops, says a conunittee of experts advising the British goveriunent. New technologies, it says, could be used to prevent the nightmare scenarios dreaded by consumers and campaigners: genes resistant to herbicides crossing into other plants creating an unstoppable superweed; plants with genes for toxic substances pollinating crops and producing poisonous food; or modified plants containing novel proteins provoking allergic reactions. The Advisory Committee on Releases to the Environment (ACRE) has issued a set of guidelines telling companies how to use the latest advances in biotechnology to minimise any risks of gene flow-the first time a regulatory body has offered such advice. "We're not saying that they are unsafe," says Brian Johnson of the government conservation body English Nature, a member of ACRE. "We're saying, yes, you could reduce the risks even further, especially the risks to biodiversity." Johnson says there will be no changes in the law to force companies to make such improvements. But if they don't, he adds, they will find it much more difficult to get their products approved. The ACRE report, which was released for consultation this week, details the tools biotech companies could use to enhance safety. But some of the technologies are still being developed, and patenting might restrict their use. "Patenting technologies such as these has serious implications for biosafety," Johnson says. "My personal view is that the technology should be made widely available." While the report puts pressure on the biotech industry to change its ways, for antiGM campaigners it poses something of a dilemma. The new technologies eliminate some of the dangers they are concerned about, but the crops will still be genetically modified. 'I think it is really encouraging that [ACRE] has started to think about these sort of issues," says Sue Mayer of GeneWatch UK. The report, entitled "Guidance on Best Practice in the Design of Genetically Modified Crops", sets out three main guidelines. First, plants should be engineered in a way that minimises the risk of gene flow to other crops or wild relatives via cross-pollination. There have already been several examples of such gene flow, including the case of the sugar beet that was accidentally endowed with resistance to two different herbicides (New Scientist, 21 October, p 6). At the moment, the only way to prevent gene flow is to set up buffer zones between closely related species. This is not 100 per cent effective. But the report outlines numerous ways of preventing gene flow altogether, such as engineering plants so they're incompatible with other strains, don't produce viable pollen, don't flower or reproduce asexually (see opposite). Controversially, this list includes "terminator" technology, a method for making crops produce sterile seeds which campaigners say would enslave farmers by making them buy new seed each year. But the ACRE report points out that there are practical as well as ethical problems with using terminator crops. The second recommendation says that as little DNA as possible should be added to plants. In particular, companies should avoid using antibiotic resistance genes as markers. Researchers use these genes as labels for other implanted genes. While the overuse of antibiotics is the main cause of antibiotic resistance, "we must not add to the risks", Johnson says. Lastly, the report recommends that genes added to plants should be expressed only when and where they are needed. For example, if foreign proteins are not expressed in the parts of plants used for food, there would be little chanct of them provoking an allergic reaction. Such an approach could also stop foreign proteins being expressed in the pollen of modified plants. There was an outcry last year when studies suggested that pollen from maize engineered to make the bacterial Bt insecticide could kill monarch butterflies (New Scientist, 22 May 1999, p 4). The report also suggests that GM traits in plants could be activated only when a specific chemical is applied to a field. AntiGM activists have attacked such technology because they think companies will use it to force farmers to buy expensive activation chemicals. But the report says that it could have benefits if used in the right way. Mayer welcomes the report because she says regulators underestimate the risks posed by the current generation of modified crops. They assume that fanners will follow rules about, say, maintaining buffer zones between crops. "That is very unlikely." Biotech companies have cautiously welcomed the report. Monsanto described it as well-considered and comprehensive. "As a leading player, we are looking at the feasibility and potential benefits of the technologies mentioned," says its spokesman Tony Combes. Mark Bailey, chair of the ACRE subgroup that compiled the report, says he very much hopes that other countries will adopt this new approach. "Nothing like this exists elsewhere," he says. Michael Le Page

More at: wwwenvironment.detrgovuk/acre/bestprac/ lndex.htm

The Next Revolution The Death of Plant Sex NS 28 Oct 2000 5

OF ALL the emerging technologies that could be used to improve the safety of genetically modified craps (see opposite), perhaps the most promising is one that would let crops clone themselves, as many wild plants do already. This phenomenon, called apomixis, could not only slam the door on accidental gene transfer, it could also benefit farmers-especially the poorest ones-because they save seeds each year from the same elite plants and replant them. "Apomixis is a winner from all perspectives," says Brian Johnson, an advisor of the British government. "We look at it as one of the ultimate-genetic isolation mechanisms." Many of the best crop strains are hybrids. But because hybrids don't keep all their valuable traits when they breed (see Diagram), farmers who want to grow hybrid crops have to buy new seed each year. The seeds produced by apomictic plants, however, are genetically identical to the parent plant. Farmers would be set up for life if hybrid crops can be made to reproduce apomictically. What's more, it would even become practical to tailor crops to suit local conditions. In apomixis, the process that halves the number of chromosomes in a female cell prior to fertilisation is bypassed. Instead, the egg retains its full set of chromosomes and grows into a clone of the female parent. Most apomictic plants neither accept pollen from other plants nor produce any themselves. This means there'd be almost no risk of gene transfer If genetically engineered plants reproduced this way. The big challenge, however, is to transfer the apomixis trait to crop plants. Efforts to create apomictic crops have been under way for decades, but researchers may finally be getting close. "People say it will be cracked in the next five years," says Johnson. A team at the International Center for Maize and Wheat Improvement near Mexico City, which has been working on an apomictic relative of maiz6 called Tripsacum, has recently found a gene that might be responsible for apomixis. "It's called elongate, and we're in the process of cloning it," says Olivier Leblanc, the head of the research project. Elsewhere, John Carman of Utah State University in Logan claims to have found a way of introducing apomixis without genetic engineering. "Our first target is sorghum," says Arden Kelton of Apomyx, a company set up by the university to commercialise the technology. At a meeting in Bellagio in Italy in 1998, many of the apomixis pioneers signed a declaration aimed at preventing multinationals from obstructing the development of apomixis. But multinationals are already in on the act. Novartis of Basle, Switzerland, for example, has a number of patents on the process. A spokeswoman for the company says, however, that it won't obstruct transfer of the technology to poor farmers. "One of the goals of the programme is to ensure these varieties are made available to subsistence farmers free of charge," she says. Andy Coghlan

Crisis time for Europe's ravaged forests NS 28 Oct 2000

TWO-THIRDS of Europe's trees are sickly, according to the latest European Commission report. "This is serious," says Frangois Kremer of the European Commission forestry division. Only 36 per cent of all broadleaf and conifer trees in Europe are healthy, says the report, released this month by the European Commission and the United Nations Economic Commission for Europe. These trees are shedding no more than the average amount of leaves and needles each year. However, one in five show signs of damage, having lost at least a quarter of their leaf canopy. The rest are visibly dropping more leaves than usual, and have been placed on a "warning list". Trees that live in the Mediterranean appear to be the hardest hit. "The causes are multiple and complex," says Kremer. Air pollution, climate change and soil degradation are just some of the problems that are facing Europe's trees, he says. "Further reduction of emissions is really needed." The commission looked at about 129,000 trees from forests in 30 different countries. Forestry experts examined trees in the summer to estimate how many leaves were left on the branches. In more detailed studies on 15 per cent of the plots they found low levels of soil nutrients in a third. About half the trees were exposed to excessive nitrogen compounds from air pollution. Nicola Jones More at: hftp:Heuropa.eu.int/comm/dgO6/foreAndex-on.htm

Telltale traces
How reliable are official tests for genetically modified food? NS 14 Apr 2001

THE tests that the US government relies on to keep foods free from genetically modified contaminants can miss low levels, claims a controversial research paper by the Iowa company Genetic ID.

The tests in question use antibodies to detect the presence of GM foods. But the companies making such tests claim the report is an attempt by Genetic ID to promote the technique it uses.

Genetic ID prepared samples of soybean containingbetween 0.1 and 10 per cent GM beans, and sent them to official testing labs. Of the samples with a GM content of less than 1 per cent, more than 30 per cent were incorrectly identified as GM-free. The company says it also has unpublished evidence that there are similar problems with the detection of Starlink maize, a GM strain not approved for human consumption because of fears that it may trigger allergies. At least one shipment of maize destined for Japan-which prohibits even traces of unapproved GM foods-was cleared by the US only to fail Japanese tests.

Genetic ID's researchers say their work argues that antibody tests should be supplemented by the technology the company uses, the polymerase chain reaction (PCR) method, which detects modified DNA directly. But critics disagree: 'This isn't good science," says Dean Layton of EnviroLogix in Portland, Maine, which produces an antibody test for Starlink. "It is a transparent attempt to undermine the competition."

Genetic ID's report admits that the antibody tests are reliable if carried out properly, Layton says. And he points out that the labs that took part were told that the tests should be performed as they are 'routinely used". Labs do not generally test for levels less than I per cent for soybeans. So if the labs usually test for a S per cent level-an acceptable level for soybean exports to japan-it's no surprise they failed to detect a 1 per cent level. All the labs reliably detected samples with a 10 per cent GM content.

Don Kendall of the US Department of Agriculture says the USDA's quality assessment of its own labs showed that the tests are being used correctly. In response to Genetic ID's report, however, it is investigating further. But Kendall doesn't expect policy to be changed to include the use of PCR. "It is too expensive and too slow," he says. Philip Cohen More at: International Journal of Food Science and Technology (vol 36, p 3571

Darwin strikes back
One modern idea about evolution turns out to be wrong NS 28 Oct 2000

CHARLES Darwin can still teach scientists a thing or two. Research on two creatures' mating habits has overtumed half a century of dogma by showing that natural selection alone can help create new species, just as Darwin predicted. Since the 1940s, biologists have believed that a species could split only if a geographical barrier-such as an ocean or a mountain range-separated two populations and prevented them from mixing. But Australian and American scientists have found that this isn't necessarily so. They have shown that natural selection can change the way both fish and flies recognise their prospective mates, a process which can lead to two groups rapidly diverging, even when they live together in the same place. This process of reproductive isolation only takes a dozen generations or so, making it faster than anyone thought possible. The findings raise the intriguing possibility that people could quickly split into different species. Given the right conditions, groups of humans might evolve so fast that they become isolated from each other in as little as 300 years. "There's no reason why mate recognition in any species couldn't evolve so rapidly," says Megan Higgie of the University of Queensland in Brisbane. "I don't see why it couldn't be possible in humans," agrees Andrew Hendry of the University of Massachusetts in Amherst, although he points out that our choice of mate is complicated by cultural influences.

Higgie and her colleagues studied the effects of natural selection on Drosophila serrata fruit flies. When Higgie put these flies with a similar species called Drosophila birchii, the D. serrata males wasted half their time trying to mate the females from the wrong species, hence losing valuable opportunities to pass on their genes. But within just nine generations this selection pressure had forced them to alter t,heir pheromones to only recognise their own kind. "The trait under selection, mate recognition, is an important one," says Higgie. "Make a mistake, and you might not contribute to the next generation." Meanwhile, Hendry and colleagues at the University of Washington in Seattle studied sockeye salmon in Lake Washington. The fish had been introduced into ariver upstream of the lake in 1937, but many had taken to spawning at a beach on the edge of the lake. Hendry compared fish that spawned at the river with those that spawned at the beach. He found differences in both their appearance and their genes, even though the fish were swimming between the two areas. The genetic differences were not great, but were large enough to show that the populations had somehow become reproductively isolated from each other in fewer than 13 generations. "It is speciation in action," says Hendry. "This is the first time it has been shown to happen this quickly in the wild." Joanna Merchant

More at: Science (vol 290, p 516 and p 519)

Only the best NS 29 Oct 2000 13

WITHIN a few years it could be possible to boost the success of IVF by checking for major chromosomal abnormalities before embryos are transferred to the womb. "Potentially, this is a major advance," says Mark Johnson of Imperial College, London. At present, it is only possible to check a handful of chromosomes. But by adapting exisung techniques, Joy Delhanty and Dagan Wells of University College London were able to check all the chromosomes in 12 three-day-old embryos. Abnormalities were surprisingly common, Delhanty says. Only three of the 12 embryos had the right number of chromosomes in all their cells. The researchers used a technique called comparative genomic hybridisation (CGH). They compared the chromosomes from the embryos with ones from normal cells by staining them with different dyes. Any departures from the normal number of chromosomes, or any large deletions or insertions, show up as differences in the amount of fluorescence. Large amounts of DNA are needed for CGH, so Delhanty and Wells had to make many copies of a cell's DNA by improving on a second method known as whole genome amplification. At present the test takes three or four days-far too long for pre-implantation screening, says Delhanty. The time will have to be reduced to around 24 hours to make it practical, she says. "It'll be a year or two before it might be applied." They looked at every cell In the embryos in their study, but when the test is used for screening, technicians will only be able to test one or two. "You can never be sure that the rest of the embryo is normal," Delhanty says. Emma Young

lt started with a crash

Our Universe didn't really exist until another one bumped into it NS 14 Apr 2001 7

IT was mighty quiet in our Universe: devoid of all matter and energy. Then another universe collided with it. Suddenly space became a searing soup of particles and radiation, far hotter and denser than the centrq@'Of the Sun.

This, says a team of physicists, is how the big bang happened. The approach of the parallel universe caused the expansion of space, and the collision itself produced all energy and matter. A comprehensive description of this new theory has been submitted to the journal Physical Review D.

The model is a viable alternative to the theory of cosmic inflation, which was cooked up to solve some of the problems of classical big bang theory. According to inflation theory, the Universe underwent a brief period of exponential expansion in the first split second of its existence. "Our new model solves the same problems," says co-author Paul Steinhardt of Princeton University, who was one of the founders of inflation some 20 years ago.

So how might this primordial collision have come about? According to the theory, our three-dimensional Universe, known as a '3-brane" to cosmologists, is just one of the two boundary surfaces of a thin fourdimensional "bulk space", rather like one of the two surfaces of a CD. But there was another universe, or bulk brane, inside the bulk space which encroached on our boundary brane. When this "brane storm" led to a collision, the energy released resulted in the big bang. Unlike inflation, the brane-storm model-dubbed the "ekpyrotic universe' by the authors of the paper, related to the Greek idea of 'cosmic fire"-fits in neatly with the popular string theory of particle physics. 'That's one of the exciting things about it," says Neil Turok of Cambridge University, another co-author.

'I'm delighted to see an alternative picture for the early Universe,' says cosmologist Jim Peebles, also of Princeton. "It has been frustrating to me not to have any alternatives to inflation, which I feel has been accepted by many cosmologists too easily." As for the credibility of the new model, he says: 'I haven't heard my string theory colleagues complain. That's a positive sign."

But if there are other branes floating around in 4-D bulk space, might we be in for another big bang? Turok says it can't be ruled out. Luckily, the fact that Newton's gravitational constant doesn't appear to be changing implies we're safe from a collision for many billions of years. Govert Schilling More at: http://xxx.lant.gov/abs/hep-th/OiO3239

Heavenly twins

What if two universes popped into existence 15 billion years ago instead of just one? NS 2001

OUR Universe may have a twin. Li-Xin Li of Princeton University in New Jersey has calculated that our Universe and its sibling could be akin to two soap bubbles connected by a thin tube. 'To an observer situated far from the connecting tube, the interior of a bubble would look just like our Universe," says Li.

To find out what our Universe may be like, physicists look for mathematical solutions to Einstein's equations of gravity. Li has found an exact solution that predicts a pair of low-density, or "open' universes. The discovery, he says, was 'very surprising". The universes would have been the result of two identical big bangs. Li stresses, however, that the twins are not really shaped like bubbles. "Bubbles have positive curvature and are finite but the space of my universes is actually negatively curved, like a saddle, and infinite," he says.

A bridge known as a 'wormhole" connects the universes, says Li, and could provide a test of whether or not we live in a twin. Its presence would have an effect on the cosmic microwave background radiation-the afterglow of the big bang. We wouldn't see obvious hot or cold spots in the CMB, but there should be subtle changes in the pattern of temperatures at different length scales.

"It's conceivable that we might actually see stars or galaxies disappearing down the wormhole into the other universe or, alternatively, stars and galaxies from the other universe appearing unexpectedly in our own," says Li. "It would even be possible for a spacecraft to go back and forth between the universes."

"It's certainly a very intriguing idea," says Max Tegmark of the University of Pennsylvania in Philadelphia. "Li's solution deserves close investigation." Einstein's equations might also permit lots of universes all connected together, says Li. Some cosmologists have argued that our Universe is just one of a large ensemble of universes-a "multiverse"-each dancing to the tune of slightly different laws of physics. "My universes have the same laws of physics," says Li, but lie doesn't rule out finding universes with different laws. Marcus Chown More at: xxx.lant.gov/abs/hep-th/0102143

Against the Grain NS 3 Feb 2001

RICE last week became the first crop plant to have its genome completely sequenced, an achievement that pron-dses to unlock the genetic secrets of au major cereal crops. But the companies responsible will not make the sequence freely available on the Internet or in a scientific joumal, a decision that has caused concern among academics. "This will rank as one of the great achievements of the genomics era," says Peter Meldrum, president of Myriad Genetics, which did the sequencing in Salt Lake City, Utah. "It's the first agriculturally important crop to be sequenced, and it nourishes half the world's population." Syngenta, a Basel-based multinational, managed and funded the project. But both companies are guarding their data closely. Academics are free to ask specific questions, says Steve Briggs, of Syngenta's Torrey Mesa Research Institute in La jolla, California, who headed the project. "But we do require that if there are inventions from collaborations, we are given a chance to license them first. We won't seek to patent the rice genome, but we will protect inventions which are marketable," he says. However, plant geneticist Ottoline Leyser of the University of York says: "I'm concemed about the monopoly on information that might develop if publicly funded access to the information is restricted." Leyser is a member of an international consortium of governmentfunded labs that announced just weeks ago that they'd sequenced the first plant, a weed called Arabidopsis thaliana (New Scientist, 16 December 2000, p 14). Rice has the smallest genome of all cereals, with 50,000 genes on 12 chromosomes. This makes it a kind of Rosetta Stone for investigating genes in other cereals. "It provides an inunediate understanding of wheat, com, barley and other cereals," says Briggs.

Syngenta and Myriad have agreed to help develop new crops for subsistence farmers. "We will come up with varieties adaptable to local conditions ... and it will be conducted in a manner that will be royalty and licence-free," says David Evans, head of research at Syngenta. But pressure is growing to speed up a publicly funded effort to sequence rice, so that everyone can get access to the data. Such a project is already gathering steam in Japan, China and other Far Eastem countries. Otherwise, Leyser fears that much of Syngenta's data wifl just gather dust. "They can only exploit a tiny amount of it. The rest is sitting there doing [email protected]," she says. Gurdev Khush of the Intemational Rice Research Institute in the Philippines agrees. Using Myriad's sequence will cost time and money, he says. "It's therefore imperative that the publicly funded project continues so it's available to all." Andy Coghlan

Bad copies NS 3 Feb 2001
Do some clones lose something vital during their creation?

CLONING does not have a very high success rate. Animals are often born sickly or unusually large, and many do not live long. The reason, say scientists in Scotland, may be just a few missing carbon atoms. Lorraine Young of the Roslin Institute near Edinburgh and her colleagues have shown that when sheep embryos are manipulated in the lab they can lose some of the methyl (CH3) groups attached to their genes. They say this small rbhange alters how actively the genes produce proteins which are key to the animal's survival. The discovery may allow scientists to screen embryos produced by cloning and other test-tube techniques, allowing faulty embryos to be eliminated b#fore they are implanted into a surrogate mother. "A lot of us have been trying to nail down what kills clones," says Mark Westhusin, who clones cattle at Texas A&M University in College Station. "This is absolutely a new twist that many people are going to follow up on." For every living success story, cloning generates many animals that die of mysterious causes. Researchers at Roslin produced 277 cloned sheep embryos before achieving a live birth with Dolly. Recently, Noah the gaur, cloned from a member of this endangered ox-like species using a cow egg and a surrogate cow mother, died of an infection soon after birth. Many experts believe Noah died because of cloning-related health problems.

Some cloned animals grow huge, and often sickly, during gestation. Similar problems can arise in embryos produced by other technologies that culture them in test tubes. The Roslin researchers and others had previously found evidence that unusual levels of proteins that regulate fetal growth could be partly to blame (New Scientist, 23 January 1999, p 15). Production of some of these proteins is known to be affected by methyl groups attached to the relevant genes, so they wondered if methylation was different in enlarged animals. "We and others have been investigating the idea," says Young. "However, this is the first proof of the theory.' Young and her colleagues studied sheep produced by artificial insemination that suffered from what is called "large offspring syndrome". They found that these LOS sheep often lacked all the methyl groups on the gene for a protein called IGF2R, and that they produced 30 to 60 per cent less of the protein than normal. IGF2R helps stop the fetus from growing too large. In control animals, about 70 per cent of the same sites were methylated. Young thinks that clones may suffer from an even greater array of defects than these LOS animals because the embryos undergo greater manipulation and may therefore lose more methyl groups from more genes. Philip Cohen

More at: Nature Genetics (vol 27, p 153)

Is polar meltdown just hot air? NS 17 Mar 2001 16

THE North Pole isn't melting after all, says a researcher in Sweden. Recent reports that ice in the Arctic is rapidly disappearing have been taken as graphic proof of global warming. But a more extensive study now shows the ice hasn't thinned at all since the late 1980s.

Peter Winsor from the University of Gothenburg in Sweden looked at data from 1986 to 1997 showing sea ice thickness throughout the Arctic. The data had been collected by submarines cruising under the ice and firing sonar pulses upwards to determine its thickness. After adjusting the data to account for seasonal differences, he found the volume of ice in the Arctic had stayed nearly constant.

This contradicts a major study in 1999, which found that the thickness of Arctic sea ice had decreased by a startling 1.3 metres since 1958-more than a third of its current thickness-and continues to drop by 0.1 metres per year. Winsor says his results differ simply because they're based on more data.

"Recent reports of the demise of the Arctic ice cover have likely been greatly exaggerated," says Bill Hibler from the International Arctic Research Center in Fairbanks, Alaska. "It's probably a lot tougher than many recent reports suggest." Winsor says his study doesn't mean the planet isn't heating up. But it does point to flaws in climate models which predict that Arctic ice will be drastically affected by global warming. Nicola Jones

More at: Geophysical Research Letters (vol 28, p 1039)

Alaska's glaciers appear to be disappearing before our eyes. Are they a sign of things to come? Richard Monastersky searches for clues NS 14 Apr 2001

STANDING on North America's most visited glacier in summer, you can hear the sound of climate changing. Gurgles and babbles build to a crescendo where water cascades down holes in the ice. The N*ndenhall glacier in south-east Alaska is melting and it's raising a ruckus about it. Situated in the backyard of Juneau, the state's capital city, the Mendenhall attracts more than 300,000 visitors per [email protected], making it one of the most watched glaciers in the world. It's also become a poster child for global warming. Before the public's eyes, the glacier is shrinking. Last summer, its end point retreated up the valley by 100 metres, freeing land that had been locked under ice for centuries. Since the 1930s, the Mendenhall has lost nearly a kilometre of its length.

But glaciers can be slippery subjects when it comes to climate, and appearances can deceive. Individual glaciers can respond to many different factors, making it risky to use any one patch of ice as a global yardstick (see "Running deep", p 32). Four years ago, for instance, the environmental group Greenpeace raised the alarm when the front end of Alaska's huge Bering glacier collapsed. "Rising temperatures shrink world's largest temperate glacier," screamed the press release. Yet researchers immediately pointed out that this apparent catastrophe was part of an expected cycle. Every couple ' of decades the Bering spends several years surging down its valley. But the longer glacier is unstable, and much of the front part breaks off as icebergs, leaving the end of the glacier further up the valley again. The Bering brouhaha fits in with a larger pattern of climate catastrophe stories. With the fervour of Chicken Licken, environmentalists [email protected] taken to claiming "tbe ice is melting" at the slightest provocation, no matter what the context. The headlines of late have featured gargantuan icebergs breaking off Antarctica and open water appearing at the North Pole, without mentioning whether these events have happened before or what their significance is.

That's why glaciologist Keith Echelmeyer has taken to the skies. Flying a singleengined, two-seater plane, he is surveying some 90 glaciers from the extremes of northern Alaska down to the Cascade range of Washington State. His projeef is assessing the health of glaciers both big and small, collecting the data necessary to determine how the ice has fared across the north-west margin of North America and what it has to say about climate. The message coming ftom the first 8 years of this massive survey isn't good. "I didn't expect to see nearly as large a change," says Echelmeyer, a researcher at the University of Alaska Fairbanks. His measurements show that most of the glaciers are losing weight fast-so quickly in fact that some may not survive the 21st century.

The results could well be a sign of how greenhouse gas pollution will harm the high Arctic in years to come. But some researchers still see evidence of other potential reasons for the shrinkages besides global warming. lt was ignorance, coupled with a love of flying, that prompted Echelmeyer to start making house calls to glaciers. "People would often ask what the glaciers are doing," says Echelmeyer. "Are they all thinning?'Nobody could answer that." Before his project began in 1993, scientists regularly monitored only two out of the thousands of glaciers in Alaska. With a territory so vast and with many glaciers in remote regions, it was nearly impossible to keep tabs on these icy streams using traditional survey methods.

But the Global Positioning System and compact airborne lasers have made it feasible to track glaciers from the air. In 1992 Echelmeyer and his colleagues built a system that shoots laser light through a window on the bottom of a Piper Supercub and then catches the beam after it bounces off the glacier. By timing the length of the trip, the system can gauge the elevation of the surface relative to the plane, while GPS fixes the plane's altitude and position. The whole procedure can measure the height of the ice and snow to within 10 centimetres.

To map a glacier, Echelmeyer and a crewmate fly several passes along it. They must go low and slow, creeping along at 100 kilometres an hour about 100 metres above the glacier, following its every bump and dip. For more accurate figures, Echelmeyer sets down his plane on the glacier to measure the snow depth by hand. That's when he's run into the most trouble. "Some of the hairiest moments have been landing or taking off. Sometimes, the snow is so sticky and deep and the winds are blowing with you, and that makes it hard to take off." Sometimes he's taxied down the glacier for 3 kilometres to build up enough speed to get airborne.

If the plane won't take off, Echelmeyer lightens his load by leaving his passenger behind. Then he tries landing and taking off several times to pack down a runway from which he can lift off with his human cargo. Once, he was stuck for 2 days and had to trample down a 650-metre runway by foot, using skis and snowshoes.

Getting thinner

During the past 8 years, Echeimeyer has surveyed glaciers across some 2000 kilometres of western North America. Two of the biggest glaciers each exceeded the surface area of some American states. He expects to continue for another two years, revisiting glaciers that he studied in the early 1990s to see how they have fared since then.

When he has mapped a glacier, Echeimeyer compares his results with charts made from aerial photographs by the US Geological Survey 40 to 50 years ago. This helps determine the glacier's mass balance whether it is putting on weight or wasting away. Glaciers generally get thicker during winter snowstorms and then thin when they melt in the summer. To stay healthy, they must maintain an even mass balance, putting on at least as much as they lose. Last summer, flights over the Mendenhall revealed that it hasn't managed to keep its weight up. In the past half-century, it has thinned by about a metre each year. Most glaciers in the survey have had significant bites taken out of them. Some 90 per cent are melting more in summer than they gain in winter, says Echelmeyer. "We find in general the glaciers are thinning from 0.5 to 1.5 metres per year as an average over their entire extent. And that's measured over 40 or SO years, which is fairly big." Now he's trying to tease out what has caused these declines. is the weather warmer? Has snowfall decreased? His studies so fat indicate that temperature seems to be the main factor. "The glaciers in Alaska are giving us a clear picture that indeed something is happening to cause them to thin and that has to be climate-related," he says. The marked change has come at the same time as worldwide temperatures have shot up most dramatically. At this rate, some of the smaller glaciers don't have long to go, says Echeimeyer, pointing in particular to the Lemon Creek glacier, east of Juneau. "The Lemon Creek is now thinning 2 to 3 metres a year and it's a maximum of 200 metres thick. That's a 100 years [to go]. But it will go faster than that because if you thin a glacier, it gets less snowfall because it extends less far up the mountains. If this continues, some of the glaciers will go away in 50 years." Echelmeyer's study is filling a major gap, says johannes Oerlemans, a meteorologist at Utrecht University in the Netherlands. "His work is so interesting because there has been so little work on Alaskan glaciers," he says. While the Alps have been studied for many decades, the ice in all the Alpine glaciers combined amounts to no more than one large glacier in Alaska. "Alaska is more remote, but on the other hand it's more important because there is more ice there.11 Many glaciers elsewhere are wasting away, but only in Alaska is the rate accelerating, says glaciologist Julian Dowdeswell at the University of Bristol. It may be that Alaskan glaciers are functioning as canaries in the coal mine of global climate, showing changes before they appear in other polar regions. This doesn't necessarily mean that greenhouse warming is solely to blame, Dowdeswell cautions. Glaciers respond in a complex way to many different climatic forces, he says. "That's why it's actually quite difficult to unravel which bit is having the most influence at any one time." in fact, the rapid thinning of Alaskan glaciers in the 1990s may have been a temporary setback, according to Dennis Trabant of the US Geological Survey in Fairbanks. Since 1966 the USGS has monitored the mass balance of two Alaskan glaciers-the Wolverine near Anchorage and the Gulkana in the centre of the state-and this shows evidence of a climate cycle, Trabant says. Between 1976 and 1989 one of the glaciers thickened while the other thinned. "Since 1989, both glaciers have lost mass at an unprecedented rate up until the last couple of years. But it looks like that might be ending," he says. Trabant suggests that the glaciers are responding to a large-scale cycle called the Pacific Decadal Oscillation, which causes the climate of the northern Pacific to swing back and forth every decade or so. Some researchers suspect the PDO is in the process of shifting direction, but they won't be sure for several more years, says Trabant. If Alaska's glaciers are responding to the PDO, then they may start thinning more slowly, he predicts. "I don't think it's a lead-pipe cinch to expect the current trends to be sustained for 100 years in the future," he says. "It's just not that certain."

The Mendenhall glacier is a case in point. Summertime melting thinned the lower reaches of the glacier by 11 metres this year-similar to the average annual loss during the 1990s. But the winter of 1999/2000 deposited an unusually thick layer of snow ice blue: bergs may warn of a warming Earth higher up the glacier. So it ended up with an overall net increase in mass-something that hasn't happened in many years, says Roman Motyka, a glaciologist with the University of Alaska Southeast. It's too early to tell whether last year's gain is the start of a trend or only a blip. In a report to the US federal government, Motyka said in January that "the long-term trend at the Mendenhall has been decidedly towards glacier thinning and recession". Over the past winter, snows have once again blanketed the glacier, piling on some much-needed mass and temporarily hiding the rocks strewn across its surface. Come the warm rays of summer, though, the meltwater will once more start trickling across the glacier's surface, first as just a whisper and eventually rising into a sustained chorus. Like scores of other glaciers across the region, the Mendenhall will resume its annual battle to keep from wasting away.

Richard Monastersky is a senior writer at the Chronicle of Higher Education in Washington DC

Safety in Numbers NS 3 Feb 2001

WALLACE CRAIG cupped the lifefeathery bundle in his hands ghed. Glancing at his watch ted the time: 1.00 pm. The I September 1914, and Martha ger pigeon had just expired. ent an entire species. It was the most unlikely extinction. In the early 18th century flocks of migrating passenger pigeons had darkened the skies above eastem North America, taking three days to pass by. Hunters simply pointed a gun upwards, fired, and then got out the way as the pigeons tumbled to Earth. When the birds stopped to roost, trees broke under their combined weight. With an estimated population of somewhere between 3 and 5 billion, the passenger pigeon was the most abundant bird that ever lived. Yet by the late 1890s the species was almost extinct. A few birds found their way to zoos, but they languished in captivity and refused to breed. It was a result that perplexed Craig and his contemporaries, and today's conservationists often face a similar problem. It isn't just that living in a zoo can ruin an animal's sex life. VVhen wild species experience a population crash they too can go into free fall, even though you would think that by removing the pressure of overcrowding, the survivors would flourish. Now conservationists are beginning to realise that under-crowding itself can help drive species to extinction. It's a counterintuitive idea, but it's not a new one: the consequences of low population density were first studied more than half a century ago by American biologist Warder Allee. For decades his ideas were largely forgotten, but now an awareness of these "Allee effects" looks set to transform conservation practices. "They alter our perception about the risks facing populations that have declined markedly, even if they are not numerically tiny,' says Georgina Mace from the Insfitute of Zoology in London. "Allee effects centre on the observafion that some species find it very difficult to breed successfully once the populafion falls below a certain number or density," says Franck Courchamp of the University of Paris-Sud. "It used to be thought that such populations would simply rebound, but clearly this isn't always the case," adds Philip Stephens from the University of East Anglia. And as Allee pointed out, there are various reasons why. For some species, such as blue whales, it is simply that with only a few, solitary individuals remaining, finding a mate can prove extremely difficult. It's a little more complicated for New Zealand's giant flightless parrot, the kakapo, where dwindling numbers mean insufficient males coming together at breeding time. Male kakapos gather at leks and the females are attracted by their multiple calls-a bit of a problem when the world population is down to 54 dispersed individuals. A similar fate could await other species that use leks, such as the European black grouse and South America's cock-of-the-rock. Perhaps the commonest Allee effect occurs in species that congregate to protect themselves against predators. Animals such as flamingos and penguins just won't get into breeding mood unless they are surrounded by many other mating individuals. In such species, natural selection favours animals that synchronise their breeding because their offspring are more likely to survive the vulnerable early weeks if there are plenty of other young animals around for potential predators to pick off. "This may not be a problem for a species that is usually abundant," says Bill Sutherland from the University of East Anglia, "but can become important once it becomes rare or once people are trying to breed it in captivity." In some species, a behaviour that probably evolved as a way of swamping potential predators, seems to have developed into a near-unbreakable psychological dependence. "But Allee effects can be more subtle and complex in group-living species," says Courchamp, who was until recently, part of a team from Cambridge University studying the African hunting dog, Lycaon pictus. Once numerous and widespread, the hunting dog is now Africa's ' most endangered large camivore. 'Declines of up to 30 per cent occurred even in protected areas where other previously persecuted species like spotted hyena were increasing," says David Macdonald, director of the Wildlife Conservation Research Unit at Oxford University. The reason for this was a real puzzle. The Cambridge team was led by Tim Clutton-Brock who had previously studied Kalahari meerkats. Meerkats are cooperative breeders, which rely on helpers to raise their pups, and Clutton-Brock had found that small groups were far more likely to die out than large ones. Could the peculiar social system of Lycaon make it similarly vulnerable? Digging around in the literature, Courchamp found a treasure trove of studies showing how reduced population density could adversely affect the rate of population growth of many species. "It was all being totally ignored," he says. The team started to suspect that Allee effects might be to blame for the hunting dog's failure to flourish. African hunting dogs have a rather odd social life. When the young reach reproductive age they leave the pack with a group of up to six other individuals of the same sex. A new pack is formed when they meet a group of the opposite sex. One pair becomes dominant and they alone breed, while the rest hunt and look after the puppies. The researchers wondered whether there was a minimum pack size, below which survival was difficult. Using a mathematical model and the field observations of other researchers including Scott Creel from the University of Montana and Greg Rasmussen from Oxford University, they found there wasthree or four adults plus the breeding pair. "Smaller packs find it hard because helpers are needed for cooperative hunting and to defend kills from lions and hyenas,' says Courchamp. The problem is that these same adults must also care for the pups. "And smaller packs will send off smaller cohorts to colonise new areas," says Clutton-Brock, so the problem continues to the next generation.

"The Lycaon study was the first time an Allee effect has been fully demonstrated, and it could have major implications for the conservation of other cooperative breeders," says Clutton-Brock. Animals that have no altemative but to rely bn one another for breeding success are most at risk from this particular form of undercrowding. The effect will be strongest in species such as the naked mole-rat, whitewinged chough and social insects, predicts Clutton-Brock. Less at risk are animals that help each other to raise young but do not rely so heavily on such cooperation, including wolves, lions and marmosets. Even so, this effect may explain the slow recovery of the Ethiopian wolf following a rabies epidemic that wiped out much of the population between 1988 and 1992. Allee effects are not confined to purely social species or, indeed, animals. Those that simply aggregate may also be vulnerable. For example, hen-dock trees outcompete other species by producing acids which they pump into the surrounding soil to raise its water content and drown out competitors. The more hemlocks in any patch of forest, the more dramatic the effect. So despite the fact that the densely packed trees are competing for sunlight and nutrients, hemlocks grow faster in a crowd than when they are thinly spread. Indeed, researchers including CluttonBrock have come to the conclusion that Allee effects are widespread. 'Many species may show Allee effects When populations reach extremely low densities," he says. "However, they probably occur at a wide range of densities in cooperative species where breeding success and survival increase with group size." And the implications are far fi-om academic. Take the strongly schooling fish that make up many of the world's most important commercial fisheries (New Scientist, 27 January, p 16). North Atlantic herring stocks, for example, have failed to recover despite a 25-year fishing ban, and the annual haul of Peruvian andiovies has plummeted from 11 n-tillion tonnes in the late 1960s to less than 100,000 tonnes today. Many fisheries biologists believe that once numbers of these sorts of fish fall below a certain point, predators become a significant force. Where in the past they would have merely nibbled at the edges of vast shoals, they may now be doing enough damage to check the populafion's expansion. The effects of under-crowding can also threaten attempts to reintroduce endangered species into the wild. Australian biologists trying to establish a wild population of rare marsupials called bush-tailed phascogales, Phascogale tapoatafa, for example, first tried releasing the males and females together. But this strategy failed because the animals dispersed and then the males couldn't find the females. Once the team realised what was happening they were able to minimise this effect by simply releasing the females first and allowing them to establish and mark their territories before introducing the males, who could then track them down. Allee effects could also have major implications for the success of biological controls. Some 65 per cent of attempts to control insects and 41 per cent of agents freed to destroy weeds never became effectively established. "Most such releases flop," says Rob Freckleton from Oxford University. He believes there's good evidence that Allee effects underlie many of these failures, and points to the gorse thrip as an example. The effectiveness of this tiny insect against invading gorse plants increases in proportion to the number of thrips initially released. "Numbers used in releases are often simply too small for populations to breed," says Freckleton. "This not only wastes a lot of money and effort, it also turns people away from control agents that might have been successful if only the right release procedure had been used.'

If Allee effects are so far-reaching, why did the idea languish for 50 years? "I honestly don't know," says Courchamp, pointing out that there have always been scattered papers on the subject. Stephens points out that Allee was way ahead of his time. "The major population dynamic debates in Allee's day were about top-end regulation of populations-what prevented them from growing indefinitely, or cycling irregularly," says Stephens. "There was little concern about extinction back then, or the problems of small populations. Interest in low-end population dynamics was very limited. So the Allee effect sixnply never caught on at the time." Today concem about the biodiversity crisis has changed all that, putting Allee effects at the cutting edge of conservation concepts. Their revival also reflects the trend for thinking about conservation in behavioural biology terms. "This work on Allee effects is another illustration of the importance of individual behaviourespecially sodal behaviour-in population processes," Macdonald says. "This is vital for conservation planning. Too often people treat populations as if individuals were merely numbers, whereas the reality is that they are behaviourally complex, and management must take account of that.' But bringing this approach to mainstream conservation isn't going to be plain sailing. So far, there have been very few field studies done with Allee effects in mind, and some conservation biologists feel the approach is irrelevant to their work. "There is, for example, a lingering perception that the Allee effect is a phenomenon only of very small populations and thus of limited importance to conservationists," says Stephens. He believes that Allee effects can determine the growth and dynamics of any population, small or large. To most people who have embraced the study of Allee effects, it is the potential impact on practical conservation that fuels their research. Their only regret is that the importance of Allee's work was not recognised from the start. 'The threats of overexploitation, habitat fragmentation and so on might have been focused on sooner," says Stephens. "Conservation science might have developed earlier, with a fully developed, unifying theory to hand." Even if that had happened it would have been too late for Martha and the last few passenger pigeons.

Adrian Bamett Is a freelance writer and ecologist based at the University of Surrey Roehampton In London

Further reading: 'Consequences of the Allee effect for behaviour, ecology and conservation' by Philip Stephens and Wlillam Sutherland, Trends In &dogy and Evoluft vol 14, p 401 (1999) "Inverse density dependence and the Allee effect' by Franck Courchamp and others, Trends in Ecology and Evolution, vol 14, p 405 (1999) "Vertebrate mating systems, Allee effects and conservation' by Philip Stephens and Millam Suth@ in Vertebrate Mating System (Word Sdenftft Publishing, 2000,London)