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Genesis of Eden Diversity Encyclopedia

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US fury at EU rules ANDY COGHLAN

THE US has reacted with dismay to Europe's plans for tough laws on labelling genetically modified foods. A source at the US State Department who spoke to New Scientist slammed the proposals and branded them "unnecessary". The European Union's agriculture ministers rubber- stamped the draft rules last week after months of argument, and they will become law in around four months'time if the European Parliament gives its approval, which looks certain. "We think it's a milestone, a real breakthrough," said a spokeswoman for the European Commission. "I feel strongly that our citizens need to be able to make this choice," says David Byme, EU commissioner for consumer protection. "But I deplore scaremongering about GMOS." ,AJthough not willing to discuss Washington's reaction in detail, the State Department source denounced the new rules. The US has already warned that a trade war could flare up unless the European Union lifts its unofficial 4-year block on GM imports. "We believe the EU's moratorium on approvals of new kinds of biotechnology foods has no scientific basis, and we urge the EU to lift it," the source said. "Failing that, we're actively considering taking action through the World Trade Organisation.' If the law is approved, products that contain more than o.9 per cent EU-approved GM material will have to be labelled. That includes glucose syrup produced from GM maize, or soybean and rapeseed oil from GM plants. But no known test can distinguish between such products and those from unmodifted plants. Only products that contain levels of unauthorised GM material above 0.5 per cent will be banned. This would allow a little leeway for accidental contamination in transit or during production. Lastly, animal feed containing GM material or produced from it will for the first time need to be labelled as such. So too will fodder laced with GM-derived additives such as vitamin B2. But meat and dairy produce from animals fed GM produce will not have to be labelled. Aside from exacerbating tensions with the US, the rules could also create further divisions within Europe. Britain's Food Standards Agency, for example, says the rules are "unenforceable and impractical, and do not represent a positive move in terms of consumer choice". A spokeswoman at the FSA branded the rules a "cheat's charter". Because the laws would demand labelling of products devoid of any detectable GM material, trading standards officers would have to rely on 11 paper trails" documenting the history of the product. "We think that's absolutely open to fraud, and you'd often have to rely on the honesty of a producer in a third country," she said. But opponents of genetic engineering are delighted with the proposals. "This will send a strong message to commodity- exporting nations such as the US, Canada, Argentina and Brazil," says Lorenzo Consoli of Greenpeace. "The times when you could sneak millions of tonnes of GM soybeans and maize unlabelled into the food chain are definitely over." 0

Of mice and men ANDY C0GHLAN AND PHILIP COHEN

A newborn mouse has only 300 genes that we don't, and vice versa. Just a year after the publication of thehuman genome comes the long- awaited public version-of the mouse genome. Why are gene sleuths so keen to get their hands on this genome,and what does it mean for us?

IT'S been called the "Rosetta stone" that will unlock the secrets of the human genome. And now it has been officially unveiled. The long-awaited draft sequence of the mouse genome was published this week in Nature, just two years after a global Mouse Genome Consortium of publicly funded institutes set to work to unravel the code of "Black 6", a common lab strain. Private rival Celera said it assembled its mouse genome in April 2ool, but so far it has published details of only one chromosome. Gene sleuths have coveted the mouse genome as an instant reference manual. Although the human genome has already been sequenced, it's another matter to work out which pieces of the sequence are genes, and what all those genes are for. That's where mice come in. It's not that mice are particularly close relatives - we parted evolutionary ways with them 75 million years ago. But they are probably the most studied creatures in the world, and have long been used to test potential drugs. The standard refrain when researchers announce promising results is "yet more mice cured". Natural mutations in mice have already enabled scientists to identify the function of many mouse genes and their human equivalents. Having the entire mouse genome will make this much easier.

It also makes it possible to create deliberate mutations, to see what effect they have. That is not the Idnd of experiment you can do with people, but often a disease caused by a gene mutation in mice corresponds with a disease in humans. Finding out which mutations do what can provide vital clues to how human diseases develop and, sometimes, how to treat them. Of course, with so much work being done on mice, the key question is: just how similar to us are they? Computer analyses suggest that like us, mice have around 30,000 genes, although some think both counts are too low. Most remarkably, the results published this week suggest that we have only 300 genes that mice don't, and vice versa. For every one of the rest of our genes - 99 per cent of the total - one or more related genes have been found in mice. The only major differences appear in genes for immunity, reproduction, detoxification and, surprise surprise, smelling. "They have a vast number of differences in their olfactory receptors," says Chris Panting of the

Medical Research Council's Functional Genetics Unit at Oxford University, who has been studying the differences. Mice rely on their sense of smell for mating as well as finding food, he says. Female mice also have an larger repertoire of reproduction genes compared with us. Whereas women make a single pregnancy-specific hormone, prolactin, the genome scan suggests that mice make around 20. Early comparisons have also revealed fairly substantial differences in the liver "detox" genes. These code for enzymes called cytochrome P450s, which are needed to break down poisons, toxins and drugs. There are various types of these enzymes, and each is responsible for breaking down a different class of molecules. It turns out that mice have 84 different detox genes, whereas we have just 63. That is probably because mice encounter more toxin whose team at the European Molecular Biology Laboratory in Heidelberg, Germany, did the analysis of the detox genes. The next step is to find out exactly how each enzyme works, which chemicals they break down and how they work in tandem. That could help us understand just how relevant mouse studies are to humans. "It doesn't invalidate previous toxicological findings," Bork says. "But with the genome, we can evaluate any'failure factors'more accurately." Ultimately, it may be possible to "humanise" lab mice through genetic engineering, so that they metabolise drugs the way we do. But it would take "a hell of a lot of work", Bork says. Meanwhile, other comparisons of the two genomes are helping uncover why inheriting three copies of chromosome 21, which occurs in 1 in 70o births, causes Down's syndrome. A tri-institute team led by Stylianos Antonarakis at the University of Geneva Medical School has identified 16i genes in mice related to the 178 found so far on human chromosome 21, the smallest of our chromosomes. The team compiled an "atlas" of mouse body tissues showing when and where each of the i6i genes were activated during embryonic and adult development. It revealed genes potentially linked to all the main manifestations of Down's, including defective heart valves, facial and finger abnormalities and mental retardation. But understanding disease is not the only goal of the mouse genome project. Having both genomes will also help biologists better understand how genes work at the most basic level. The mouse genome has already thrown up one puzzle that reveals just how little we know. Many small segments of the mouse and human genomes are nearly identical, or "conserved", which suggests they do something important, and yet they do rlot appear to consist of genes coding for proteins. For example, Antonarakis found over 3000 chunks of human chromosome 21, about 5 per cent, that were identical to ones on the mouse counterpart. But only a third of these conserved regions corresponded with known genes. The rest must serve unknown functions. "Each chunk is unique, so they're all doing something different," says Antonarakis. They could help regulate expression of genes on this and other chromosomes, he says, or they may maintain the structure of chromosomes. The regulatory regions of the genome that help turn genes on and off have been notoriously hard to identify, adds Wayne Frankel of the Jackson Laboratory in Bar Harbor, Maine. Now everyone is going to look in the conserved regions to see if they can find these gene switches, he says. Although pleased with their curtain-raising work, researchers in the consortium, which includes the Sanger Center in Cambridge and the Whitehead Institute in Boston, say that it is just the beginning. And there are still a few loose ends: the mouse DNA came from females, for instance, so the Y chromosome has yet to be sequenced. Already some are saying we need to sequence yet more genomes to settle questions about discrepancies between us and mice. The pufferfish's compact genome was revealed earlier this year (New Scientist, 3 August, p ig), but it is a very distant relative. Next up could be the dog, cat, chicken and, of course, the chimpanzee. With the pace hatting up as each new sequence is published, there may not be long to wait.

Gas planets grow in next to no time

Planets can form around a newbom star in just a few hundred years, say astronomers who have modelled the process. Conventional theory says planets form when dust and ice particles in the disc around a young star suck together, gradually forming lumps with gravity strong enough to attract more planets but too slow to explain how outer gas giants form, as radiation ftm neighbouring stars would blow arty gas away long before clumps grew big enough to collect more. In 1998, Alan Boss of the Camegie Institution cyf Washington suggested that denswuctuations in the discs could fidrm dense clumps that rapidly collapse into giant planets. But when he tiled it in computer models, the clumps dispersed. Now another team has turned the clumps into planets. The key was a model detailed enough to mwive the struggle between competing forces in the disc, says Tom Quinn of the University of Washington in Seattle. While gravity pulls particles together, clumps at slightly diffLIrent distances ftm the star orbit at different speeds, pulling them apart. Gravity wins in Quinn's model (Science, vol 298, P 1756). "At the end of several hundred years, we have half a dozen Jupiter-sized bodies," he told Newsdentist. "The calculation is exciting because it makes a planetary system all at once and veryfast," says Richard Durisen, an astronomer at Indiana University, Bloomington. But he'd like to see the team model other effects such as heating, to see how that affects their results. Jeff Hecht

Earth's ancient heat wave gives a taste of things to come JEFF HECHT

IT'S a nightmare scenario - slowly rising sea temperatures trigger the release of massive amounts of methane that dramatically amplify the/greenhouse effect, causing runaway global warming. Hopefully it won't happen, but if lt does it won't be the first time. This exact chain of events was played out 55 million years ago. Tremendous amounts of the powerful greenhouse gas methane are stored in icy hydrates under the seabed and in permafrost. The total amount of carbon in the hydrates is an estimated lo,ooo gigatonnes, twice that in the reserves of all other fossil fuels combined and more than enough to dwarf the 750 gigatonnes of carbon in the atmosphere as carbon dioxide. if today's warming continues and deep-sea temperatures cross the threshold at which methane hydrates melt, huge amounts of methane could be released, triggering drastic global warming. It isn't known how likely this is, but researchers have shown that something similar happened at the end of the Palaeocene epoch. Fifty-five million years ago, a gradual warming of the oceans preceded a dramatic shift in carbon isotope ratios and a steep jump in water temperatures - precisely the pattem expected if gradual warming melted the hydrate reserves. Looking at what happened in the Palaeocene helps to answer two crucial questions: how much of the methane can be released at once, and how that would affect climate. The temperature hike at the end of the Palaeocene is known to be one of the sharpest in the geological record. Within a few thousand years, sea surface temperatures soared by up to 8 'C, while deep water warmed by 5'C. Now a team led by Deborah Thomas of the University of North Carolina at Chapel Hill has analysed levels of carbon isotopes in hundreds marine plankton shells, to pin down the sequence of events for the first time (Geology, vel 30, p lo67). Crucially, they found that sea temperatures began rising gradually before the first evidence of methane release - a sharp drop in carbon-13 levels in surface- dwelling plankton - making it hard to find any other explanation for the isotope shifts (see Graph). Some 1200 gigatonnes of carbon was released as methane at the end of the Palaeocene, says Thomas, "comparable to the size of the hydrate reservoirs at the time". Once sea temperatures crsssed a certain threshold, all the hydrates were released in a cascade of bursts, each causing more warming that triggered further releases. Temperatures then remained high for the next 200,000 years. The drastic changes were bad news for deep-sea plankton, which suffered widespread extinction. But the rise in temperature benefited mammals, which evolved into new forms and spread around the globe. Thomas is cautious about comparing the present to the past. In the Palaeocene "we are dealing with a climate vastly warmer than we know today", she says. The planet lacked permanent ice caps, and the waters off Antarctica where she took her samples were about as warm as those off San Francisco are today. Yet today's ice sheets pose their own risks. When large volumes of ice melt, this can disrupt the flow of deep waters and change climate significantly. "The trigger is a lot touchier today than it was 55 million years ago," she told NewScientist.

Now we can soak up the rainbow

SOLAR power is set for a boost with the help of a material that can soak up energy from almost all of the Sun's spectrum. lt should allow solar calls to jump In emdency from today's best of 30 per cent to 50 per cent or higher. Solar cells use layers of semiconductors to absorb photons of sunlight and convert them into electric current. But each different semiconductor can only use photons at a specific energy - Its "bandpp". Today's best cells have layersof two different semiconductors stacked together to absorb light at differerrt energies but they still only manage to use 30 per cent of the Sun's enew. Theorists have calculated which two bandgaps would give a ma)dmum effldency of 50 per cent, but undi now they have not had the semiconductors todothejob. Now Wiadek Waluklevvia and his team at the Lawrence Berkeley National LabordWry Indium gallium nitride absorbs more of the Sun's energy than today's best alternatives.

In Callfbmia have found a material that fits the bill - a semiconductor called indium gallium nitride (InGaN). Byvarying the ratlo of Indium to gallium In different layers, they were able to tune InGaN's bandgap to match the criteria exactly. And because the range of the bandpp matches the solar spectrum so peftft (see Diagram), a cell could use muhiple layers tuned to bandgaps across the range to squeeze out even more energy. Walukiewla and his colleagues outline theirvision atthe Materials Research Sodety meeting In Boston this week. They say all their studies of the material suggest lt would be perfect fbr solar cells. For example, InGaN compounds seem immune to the effects of fauft lines that form when different semiconductors are grown In adjacent layers. These cradts." cripple some semiconductors blrt blue"o lasers buntftm InGaN glow brightly even though they are riddled with defects. This resilience could prolong the life of solar cells in space, where fluctuating temperatures and cosmic rays damage solar panels on satellites. There's one catch. Scientists had previously overlooked InGaN because its bandgap range was thought to be much smaller - data books quote the lower limit to be twice as high as Walukiewia daims. The diftrence may be due to the purity of the semiconductor. The samples Walukiewicz tested were made using a painstaking, and prohibitw* expensive, method to grow very pure crystals of InGaN one atomic layer at a time. The team now hopes to collaborate with the National Renewable Energy Laboratory In Colorado to tryto build cheap InGaN solar cells. Jenny Hogan

The spice of life

PlanetEarth is in the throes of one of the six great periods of mass extinction in its history. Can we get by with fewer species?

THERE was great news for sea horses, basking sharks and whale sharks last month. The big-leaf mahogany tree may also have been celebrating in its own woody way. The good news was that, against all the odds, a meeting in Chile of the UN Convention on Trade in Endangered Species (CITES) had voted to control international trade in these creatures. Decisions like this give hope that the tide of opinion is turning in favour of tough international legislation to preserve biodiversity. They make it less likely that endangered trees will end up as coffee tables, that the only surviving sea horses will be swimming in aquaria, and that the remains of the last shark's fin will be floating menacingly in a bowl of Chinese soup. It seems biodiversity has become a buzzword beloved of politicians, conservationists, protesters and scientists alike. But what exactly is it? The Convention on Biological Diversity, an international agreement to conserve and share the planet's biological riches, provides a good working definition: biodiversity comprises every form of life, from the smallest microbe to the largest animal or plant, the genes that give them their specific characteristics and the ecosystems of which they are a part.

In October, the World Conservation Union (also known as the IUCN) published its updated Red List of Threatened Species, a roll call of 11,167 creatures facing extinction - 121 more than when the list was last published in 2ooo. But the new figures almost certainly underestimate the crisis. Some 1.2 million species of animal and 270,000 species of plant have been classified, but the well-being of only a fraction has been assessed. The resources are simply not available. The IUCN reports that 5714 plants are threatened, for example, but admits that only 4 per cent of known plants have been assessed. And, of course, there are thousands of species that we have yet to discover (see Figure, p 3). Many of these could also befacingextinction. Why the fuss? Does it really matter if there are fewer species of snail or beetle in the world, if some unknown plant species ceases to exist or if the gene pool of a rare species is shrinking? In short, yes. Biodiversity is the basis of a healthy, balanced global ecology capable of sustaining life on Earth. A diverse ecosystem is a stable ecosystem because it is complex and flexible enough to be self-regulating. Earth's air and water, for example, are kept pure through the action of a wide range of organisms. Even the humblest creatures play their part. Through decomposition, dead matter is recycled and often detoxified in the process. For instance, microorganisms in soil and water convert toxic ammonia to nitrate ions, which are then taken up and used by plants. The atmosphere and the world's climate are stabilised by plants through photosynthesis, absorbing carbon dioxide and producing oxygen. A wide variety of plant life reduces the chances of flooding and drought. Roots hold the soil together and absorb vast amounts of water that is then evaporated into the atmosphere through transpiration. Conversely, plants that are tolerant of low water levels help to prevent desertification by maintaining a micro- environment under their canopy that reduces evaporation and run-off, and maintains fertility. Plant pollination, seed dispersal and nutrient recycling in systems such as the nitrogen cycle all maintain healthy ecosystems, and all depend on high levels of biodiversity. Some of these systems are so efficient we have harnessed them to improve our own personal environment. Sewage- treatment works are one of the best examples. Microbial decomposers are kept in huge quantities and given ideal conditions to break down our waste into relatively harmless substances that can safely be discharged into rivers or the sea, or even be used as fertiliser.

Healthy, varied ecosystems deliver many direct and indirect benefits. In agriculture, the wild relatives of livestock and crops provide a reservoir of genetic diversity that can be drawn upon to develop improved breeds and varieties. This natural resource will become all the more important as the world comes to terms with climate change, providing genetic characteristics that will allow crops to thrive despite changes in temperature and rainfall. of course, plants are more than just food. For thousands of years the forest and savannah have been our medicine chest. And now the pharmaceuticals industry draws upon this huge natural resource to develop new drugs. Some 56 per cent of the top iso prescribed drugs in the US are based on chemicals derived from plants, but only 1 per cent of the 25o,ooo known species of tropical plant have been screened for potential pharmaceutical use. Until we have a better idea of the diversity of plant life on Earth, we cannot know how many more life-saving drugs are waiting to be discovered. on a geological timescale, more species have become extinct than have survived on Earth to this day. Most, if not all, species become extinct eventually. However, there has to be a balance between the rate of extinction and the creation of new species. According to Donald Levin, a botanist at the University of Texas, Austin, the rate of extinction now runs at between a hundred and a thousand times the natural rate. He estimates that on average a species of animal or plant becomes extinct every 20 minutes, making our times one of the six great periods of mass extinction in the history of the Earth (see "Mass extinctions", Inside Science No. 126). Much of the observed loss of biodiversity in recent years has been either directly or indirectly the result of human activities. Across the globe, large areas of land are now devoted to growing food crops, and in these areas biodiversity has been virtually wiped out as acre upon acre of land is covered with the same plant species. When clones of plants are used, genetic diversity is reduced even further. Herbicides and pest control can mean that the number of species in some areas is more or less down to one.

Razed to the ground

Another major impact of farming practices is the destruction of forests and the desertification that often accompanies it. Slash-and-burn farming continues to wipe out huge tracts of tropical rainforest. As agriculture and habitation spread into the remaining areas of wilderness, many other species will lose their habitats. Even when the habitats themselves are not destroyed, pollution can upset the ecological balance or introduce toxins. Sometimes the loss of a single food plant due to farming practices, habitat destruction or pollution can lead to widespread loss of biodiversity if that plant is a key component of several food chains and webs. At sea, overfishing on a massive scale threatens the complete loss of certain species in particular areas. Recent research on New Zealand snappers has shown that overfishing delivers a double whammy to biodiversity. As fish populations get smaller, only a few fish seem to breed successfully in each generation. Most of the surviving offspring are genetically related to a small number of parents, so not only is the overall number reduced, genetic diversity is too. The long-term prognosis isn't good. Many scientists now believe that the world's climate is changing as a result of the burning of fossil fuels, forest destruction and intensive livestock farming (pigs, sheep and cattle produce vast quantities of the greenhouse gas methane). The UN intergovernmental Panel on Climate Change estimates that global surface temperature will rise on average by between 1.4 and S. 8 'C by the end of the century. Rising temperatures have a major effect on many ecosystems and inevitably lead to loss of diversity, particularly as the changes seem to be happening so fast that evolution is unlikely to keep up. Some species are more sensitive to temperature change than others. A rise of just 1 'C could lead to the extinction of New Zealand's tuatara, a reptile that has been described as a "living fossil" because it first appeared at the same time as the dinosaurs. Recent research at Victoria University in Wellington showed that at 21 'C, 96 per cent of all tuatara eggs are female, whereas at 22'C they are all male. So it seems

GEEKS to THE RESCUE

The Natural History Museum in London is home to millions of specimens from all over the world, collected ant several hundred years. At each specimen In the vast collection is on a handwdfull or "Nm Index card. EverY time a new specimen Is sent to the museum for ldendfKation, the Index @m has to be laboriou!dy searched by hand. So scientists at the museum and at the University of Essex are developing a MM called VWM that will scan and lnterpfetthe canb and transfer the lnfbrmation they contain to an I based database and paper oulogue- Another pmblem rath identivng orpnwm is that a number of different dassmcation @ have developed over the years. Pro is a computer program that compares different classifications. it not only allows scientists to use the best asWU of several @s, lt also helps to avoid an overestimation of biodiversity, by ensuring orpnwm don't appear more than once under different names.

It is likely that the tuatara, an animal that survived the cataclysm that led to the extinction of the dinosaurs, and doubtless many other species, will fall victim to global warming. The risks to biodiversity are not evenly spread around the world (see Figure, p 2). Certain areas are much more vulnerable - particularly small, isolated populations such as islands, rainforest fragments, coral reefs, bogs and wetlands. Many of these areas also have particularly rich diversity of flora and fauna, so if the ecosystem is damaged many species will be lost. Aside from rising sea levels as a result of global warming, islands are vulnerable to industrial exploitation for resources such as oil and minerals. Tourism also takes its toll. Coral reefs - some of the most species-rich environments on Earth - are very sensitive to pollution and changes in water temperature and depth. Bogs and wetlands are often drained for building projects or farming, to tap into oil and gas reserves or extract peat. They are also susceptible to changes in climate. We may not know what we're losing until it's too late. To avoid failing into that trap, we need to measure biodiversity. The number of different species in a particular area is a useful basic index of biodiversity, but the concept is much more far- reaching. The differences between individuals in a species, between populations of the same type of organism, between communities of different organisms and between ecosystems are all features of biodiversity (see Figure, p 1). So a particular habitat's overall health can be gauged from the diversity of species living there, both in terms of the total number of species and the range of animals, plants and microorganisms. But some habitats are more precious than others. Suppose the number of species in a lo metre by lo metre "transect" of a garden were compared with a similar transect of woodland. The garden would almost certainly show a far higher number of species - it has greater biodiversity per square metre. But which area is more biologically important? Clearly, not all biodiversity has equal value from a conservation point of view. And there are times when the presence of a single species makes all the difference. Imagine there were two areas of Scottish woodland threatened by a road-building project, each with identical levels of biodiversity and almost identical species, except that one is home to the capercaillie - a turkey-sized bird that is not uncommon in northern Europe but is rapidly heading for extinction in Scotland. Which should be protected from the bulldozers? The one that's home to the capercaillie would win hands down. An assessment of biodiversity doesn't end there. Even supposing an endangered species were sighted in an area, does it live there or is it just passing through? A single individual does nothing to preserve biodiversity - a breeding population is needed for that. The way in which observations are made also has a major effect. Each technique has its advantages and disadvantages. For example, light traps are often used to capture nocturnal flying insects, but the geographical range of the insects is unknown. We don't know where they've flown from. Beating the branches of trees and collecting what falls out is a common way of sampling insects, but this can mean those living at the tops of trees are overlooked. A weevil population in Richmond Park in London was ignored for years because the researchers used this collecting technique. Another increasingly common and effective strategy is to spray the entire tree with an anaesthetic gas then collect everything that falls to the ground. But even this technique has its limitations, because organisms that live in the bark are unlikely to be dislodged. Another major hurdle is recognising and categorising the thousands of different species (see "The species enigma", Inside Science No. 1 1 1). Fortunately, new technologies are playing an increasingly important role in classification. For many years, species have been identified by careful observation of their physical features. Now DNA technology means that species can be compared at a genetic level, greatly increasing our understanding of biodiversity both within and between species. Information technology is also proving invaluable. Vast and cumbersome paper filing systems are being replaced by easily searched databases, making identification of new specimens easier, and new software is helping to reconcile different classification systems (see "Geeks to the rescue", p 2). Not all techniques for measuring biodiversity rely on such high-tech methods. Scientists trying to gauge the size of populations of elusive creatures often resort to counting dead or trapped animals, and extrapolate this figure to estimate the size of the total population. For example, in rural Britain one effective if gruesome way of doing this is to check on "road kill" numbers - the more squashed badgers or hedgehogs counted along a particular stretch of road, the higher the numbers will be in the local population. It is important to develop a picture of the diversity of life on Earth now, so that comparisons can be made in the future and trends identified. But it isn't necessary to observe every single type of organism in an area to get a snapshot of the health of the ecosystem. In many habitats there are species that are particularly susceptible to shifting conditions, and these can be used as indicator species (see "How are we feeling today?", below). In the media, it is usually large, charismatic animals such as pandas, elephants, tigers and whales that get all the attention when loss of biodiversity is discussed. However, animals or plants far lower down the food chain are often the ones vital for preserving habitats - in the process saving the skins of those more glamorous species. These are known as keystone species. By studying the complex feeding relationships within habitats, species can be identified that have a particularly important impact on the environment. For example, the members of the fig family are the staple food for hundreds of different species in many different countries, so important that scientists sch-netimes call figs "jungle burgers". A whole range of animals, from tiny insects to birds and large mammals, feed on everything from the tree's bark and leaves to its flowers and fruits. Many fig species have very specific pollinators. There are several dozen species of fig tree in Costa Rica, and a different type of wasp has evolved to pollinate each one. Chris Lyle of the Natural History Museum in London - who is also involved in the Global Taxonomy Initiative of the Convention on Biological Diversity - points out that if fig trees are affected by global warming, pollution, disease or any other catastrophe, the loss of biodiversity will be enormous.

A sea otter's garden Similarly, sea otters play a major role in the survival of giant kelp forests along the coasts of California and Alaska. These "marine rainforests" provide a home for a wide range of other species. The kelp itself is the main food of purple and red sea urchins and in turn the urchins are eaten by predators, particularly sea otters. They detach an urchin from the seabed then float to the surface and lie on their backs with the urchin shell on their tummy, smashing it open with a stone before eating the contents. Urchins that are not eaten tend to spend their time in rock crevices to avoid the predators. This allows the kelp to grow - and it can grow many centimetres in a day. As the forests form, bits of kelp break off and fall to the bottom to provide food for the urchins in their crevices. The sea otters thrive hunting for sea urchins in the kelp, and many other fish and invertebrates live among the fronds. The problems start when the sea otter population declines. As large predators they are vulnerable - their numbers are relatively small so disease or human hunters can wipe them out. The result is that the sea urchin population grows unchecked and they roam the sea floor eating young kelp fronds. This tends to keep the kelp very short and stops forests developing, which has a huge impact on biodiversity. Conversely, keystone species can also make dangerous alien species: they can wreak havoc if they end up in the wrong ecosystem. The cactus moth, whose caterpillar is a voracious eater of prickly pear, was introduced to Australia to control the rampant cacti. It was so successful that someone thought it would be a good idea to introduce it to Caribbean islands that had the same problem. it solved the cactus menace, but unfortunately some of the moths have now reached the US mainland - borne on winds and in tourists'luggage - where they are devastating the native cactus populations of Florida. Internationally, the problems of loss of biodiversity have been aired and recognised, but that's the easy part. Agreeing on a course of action is fraught with difficulty because so many of the threats result from the way of life the developed world enjoys and the developing world wants to emulate - a way of life based around burning fossil fuels and eating a diet rich in meat. Despite these problems, steps are being taken in a number of ways to conserve biodiversity. organisations like the Convention on Biological Diversity work with groups such as the UN and with governments and scientists to raise awareness and fund research. A number of major international meetings - including the World Summit on Sustainable Development in johannesburg this year - have set targets for governments around the world to slow the loss of biodiversity. And the CITES meeting in Santiago last month added several more names to its list of endangered species for which trade is controlled. of course, these agreements will prove of limited value if some countries refuse to implement them. There is cause for optimism, however. There seems to be a growing understanding of the need for sustainable agriculture and sustainable tourism t; conserve biodiversity. Problems such as illegal logging are being tackled through sustainable forestry programmes, with the emphasis on minimising the use of rainforest hardwoods in the developed world and on rigorous replanting of whatever trees are harvested. CITES is playing its part by controlling trade in wood from endangered tree species. In the same way, sustainable farming techniques that minimise environmental damage and avoid monoculture are becoming increasingly popular. Action at a national level often means investing in public education and awareness. Getting people like you and me involved can be very effective. Australia and many European countries are becoming increasingly efficient at recycling much of their domestic waste, for example, preserving natural resources and reducing the use of fossil fuels. This in tum has a direct effect on biodiversity by minimising pollution, and an indirect effect by reducing the amount of greenhouse gases emitted from incinerators and landfill sites. Preserving ecosystems intact for future generations to enjoy is obviously important, but biodiversity is not some kind of optional extra. Variety may be "the spice of life", but biological varietyisalsoourlife-supportsystem. 0 Ann Fullick is a science educator based in Dorset