Bijensterfte, oorzaken en gevolgen

The Times, May 6, 2010
Can the struggling honeybee be pulled back from the brink by a hive of scientific industry?

Once a month, Dr Margaret Couvillon takes a pair of forceps, gently places a sacrificial bee on her arm and waits for it to sting her. “I don’t want to have to stop working with them,” she states as she explains her allergy-prevention strategy. “I love my bees.” Such dedication in the line of duty is common in the Laboratory of Apiculture and Social Insects (LASI) at the University of Sussex. Here members of one of the largest groups of bee scientists in the UK devote their days to a small stinging insect that swarms in observation hives on their desks and hums in colonies outside their front door.

“We produce scientific research, not honey,” states Professor Francis Ratnieks, the head of LASI. The only Professor of Apiculture in the UK, he is one in a long line of scholars captivated by the bee. While Aristotle contemplated the lessons of the hive, Emily Dickinson penned poems to its inhabitants.

But Professor Ratnieks’ focus has a more practical application. LASI is the centre of the four-part Sussex Plan: designed to advance our understanding of the failing health of the honeybee.

Around the turn of the 20th century, there were a million hives in the United Kingdom. Today this number has dropped to 280,000, in part because of a natural decline in beekeepers (the National Bee Unit estimates there are currently around 37,000). But a couple of years ago, more alarming news about mysterious bee diseases started to appear in the media. Suddenly losses were much more extreme than the typical 10 per cent that die each winter. In 2007/2008, a survey by the British Beekeepers’ Association (BBKA) showed a decline of 30.5 per cent. The following winter the figure was 19.2 per cent.

The spectre of colony collapse disorder in the United States created even more panic. This poorly understood American disease had resulted in massive hive losses in a nation where honeybees are responsible for $14.6 billion of crop production. Might British hives go the same way?

Although we are not on a par with the United States, estimates suggest that bees bring more than £165 million a year into the British economy. Honeybees pollinate 90 per cent of our apples, as well as many other types of fruit. “People like the idea of English apples pollinated by English insects,” says Martin Smith, president of the BBKA. “We can survive without crops that are pollinated by these insects, but it would be a very grey system.”

The threat to our orchards and honey caused a rash of speculation. “I think a lot of people wanted a name and everyone jumped on colony collapse disorder,” says Dr Juliet Osborne, a scientist at Rothamsted Research. In fact, the mysterious American disease is not behind the decline of Britain’s bees. As new research shows, their problems are explicable. Nonetheless, the hype fired the imagination of the British public and loosened private and government purse strings. Concerted lobbying by the BBKA led to increased funding and a £10 million Insect Pollinator Initiative is due to be allocated at the end of June.

“There has been something of a wake-up call about honeybees,” says Professor Ratnieks. “People in this laboratory are trying to do something useful for them on top of their basic research.” In his case, “something useful” refers to the Sussex Plan. This examination of the health, foraging habits and hive maintenance of healthy bees is designed to produce research that ultimately has a practical application for British beekeepers. “We have to study bees in the round, not just those that get sick,” Professor Ratnieks says. “If we monitor hives when they’re healthy, then if they do die we can see what’s causing it.”

The scientists behind the Sussex Plan believe that one contributing factor to the decline of the British bee lies in the intensification of agriculture in this country — 97 per cent of herb-rich meadows and 20 per cent of heather moorland have been lost since the 1950s. More efficient pesticides mean there are fewer flowering weeds in fields. “Even if we solve all the disease problems, intensified agriculture means the wildlife is squeezed out,” says Professor Ratnieks. “Where are they going to forage? Even a healthy animal’s got to eat.”

Dr Couvillon is employed to look for the answer: an answer that comes directly from the bees themselves. In 1973, Karl von Frisch won the Nobel Prize for his efforts in decoding the waggle dance. Honeybees use this set of movements to communicate with the hive about fertile food sources. By unpicking their dancing, scientists can work out how far afield bees must travel to meet their nutritional needs.

Inside the laboratory, a camera trained on the observation hive beams a picture on to a large television screen, where bees magnified to the size of mice swarm around. The Sussex morning is grey and rainy and few of the insects seem inclined to fly out on a food-gathering trip. But every so often, one stops and rotates, shaking her body as she does so. The camera ensures their every dance move is recorded for posterity — and future research papers.

Dr Couvillon has five undergraduates working ten hours a week to keep up with the decoding of the mesmerising dance. To date, they have decoded 1,124 dances. Each one gives slightly different information. By measuring the precise angle of the bee’s body and then comparing it with the position of the Sun, Dr Couvillon can estimate the direction of the food source. The longer the dance continues, the further away it is. Quality is estimated by repetition: the more times the bee dances, the better the food. The laboratory recently tracked one waggle dance to a patch of crocuses in an adjoining wood.

But the dance gives scientists more than directions. “It’s important to remember how energetically costly it is to forage far away. They’re not going to fly if they don’t have to,” says Dr Couvillon. The farther the flight, the harder the bees are having to work for food. Early results suggest that, while they travel an average of 710 metres in March, they must fly 3,950 metres for food in August. Professor Ratnieks hopes that this research could eventually result in land managers planting more trees that flower in the summer. “Let’s get the bees to tell us which parts of the landscape are good for them. If we know what they like, we can understand more about how to help them,” he says.

Dr William Hughes, from the University of Leeds, also cites the depletion of natural resources as part of the bee’s decline. He believes that colony stress is caused by many factors, from intensive agriculture to accumulated pesticide poisoning. “I think we need far more basic research on the interactions between multiple factors ­— insecticides, food, resources, sub-lethal effects of diseases,” he says. “Most research tends to be short term and focused on a single factor to be better able to get clear results. We’re missing a whole additional level of complexity underpinning it all, which is probably where the answer lies to the problems that they have in the United States and that we may have at some point in the future.”

His own work may provide some answers.

Dr Hughes focuses on the various honeybee parasites that routinely weaken and sometimes wipe out hives. “There’s been lots of focus on the diseases that kill honeybee colonies, such as varroa,” he says. “But the angles of my research are these other parasites that people ignore. They might stress colonies and, in combination with everything else, cause us to lose them.” These include diseases well known to beekeepers such as chalk brood fungus, which kills every larva that it infects and nosema apis, which causes dysentery in the hive and has recently shown a more virulent strain.

While Dr Hughes examines the impact of these diseases, the Sussex scientists are trying to find a way around them. The first stage of their plan involves research into disease-resistant, “hygienic” honeybees. If larvae and pupae die inside the hive, the remaining debris can cause diseases to spread. The dead brood also provides a fertile breeding ground for the varroa mite: a small reddish creature that attaches itself to the honeybee and weakens it. Varroa is the scourge of British beekeepers and an increasing problem, owing to the mite’s resistance to traditional chemical treatments. The hygienic honeybee provides the apiary equivalent of a good spring clean. These bees carry a gene that causes them to move dead brood out from inside the hive. This prevents the spread of disease and disrupts the reproduction cycle of the varroa mite.

About 12 per cent of British hives are naturally hygienic. But LASI is experimenting with intracolony selection, a process that aims to pass on the hygienic gene. “Bees do have defence mechanisms against diseases. Hygiene is a natural one. We want to enhance it a bit,” says Professor Ratnieks. Naturally hygienic hives are identified by killing brood with liquid nitrogen and seeing if the bees clean it away. The poison is poured through a cylinder, which had a former life as a tin of peas from Asda. “Good research isn’t good because you throw money at it,” says Professor Ratnieks. “It’s good questions and good people.” By assessing which hives are hygienic, the scientists can breed a new colony of self-cleaning bees, ultimately passing hygienic queens on to beekeepers.

Most scientists stress the importance of both basic and applied research: enhancing an understanding of the bee and its problems simultaneously. At the University of Sheffield, Dr Stephen Martin studies virus evolution, among other things. Previous research showed that the varroa mites act as a transmission route for honeybee virulents, sending diseases such as deformed wing virus and acute paralysis virus directly into the bee’s bloodstream. His team hopes to examine more closely how this transmission works, establishing a viral model system that could be used to shed light on other species. “Bees as a model system are fantastic because we can manipulate them brilliantly and we have this 100-year history at our fingertips,” he says.

Dr Martin’s work is funded by a Natural Environment Research Council grant. This external support is vital for research scientists.

At Rothamsted Research, Dr Osborne has just begun a £1 million project funded by the Biotechnology and Biological Sciences Research Council and Syngenta. She lost 20 per cent of her colonies over the winter and is keen to work out what’s going wrong. “The new project looks at whether there is an interaction between what’s happening inside the hive — disease, etc ­— and what’s happening outside,” Dr Osborne says. “Some suggest that it might be disease causing losses, others think it’s nutritional elements and we think it’s a combination of the two. But no one’s got good data yet.”

It is this missing data that research scientists across the country are working hard to provide. As part of the Food and Environment Research Agency, the National Bee Unit (NBU) in Yorkshire also helps to fill in the blanks. As the largest bee health organisation in the UK, it works with more than 80 scientists and runs the BeeBase health database. Its field inspectors assess hives throughout the country, as well as gathering data from its own 160 colonies.

Although the NBU was unable to speak during the election campaign, it confirmed that it has six proposals through to the second round of the Insect Pollinator Initiative (IPI). Dr Martin and Dr Hughes are also in the running for the £10 million allocated by Defra and other organisations. The BBKA, which lobbied for more research money in a 140,000-strong petition, is happy with the grant but points out that the funding is small in comparison with the bee’s economic value. The BBKA remains concerned that not enough of the money will go directly to the bee. “Honeybees are the most important pollinators,” says Martin Smith. “Our concern is that a reasonable proportion of that money is spent on them. We are keeping up the pressure to ensure that funding goes towards them.”

Some scientists have also expressed concern that the funding may be spread too thinly. But others, such as Dr Martin, believe that a multi-disciplinary approach is important. “I suspect there’ll be a lot of pressure to make sure the majority is spent in honey bees but I hope the panel will get the balance right,” he says. “We know precious little about how other pollinators are doing and I think widening the brief can only benefit us.”

LASI budgeted £2 million to carry out the Sussex Plan and must still raise more than £1 million. Their IPI proposals were unsuccessful, to the surprise of Professor Ratnieks. “It seems strange that practical projects aimed at helping the honeybee and with a high chance of success have been turned down,” he says. But he remains pleased with the funding they have received from elsewhere. The BBKA, Rowse Honey and Burt’s Bees have offered financial assistance. Schoolchildren, entranced by the waggle dancers, raised money from ice-cream sales.

Dr Couvillon received sponsorship from The Nineveh Charitable Trust after trustees read a letter that Professor Ratnieks wrote to The Times.

But the buzz around the bee has brought more to the research community than additional funds. It has also increased scientific interest. “Quite a number of scientists who have not worked with bees before have started to look at them as a model system,” Dr Hughes says. “They include virologists and molecular biologists.” Dr Martin is similarly excited about the chance to work with acarologists — scientists who specialise in mites such as varroa.

Meanwhile, those of us with a less scientific bent are also becoming more involved. The BBKA reports that membership numbers have soared by 50 per cent over the past five years. In 2009, 4,000 new beekeepers signed up, bringing its membership to 17,000. These beekeepers are also investing more in their colonies. The price of starting a hive has now risen to about £100. If supply and demand has anything to do with it, the bees are in good health.

The BBKA president Martin Smith’s own apiary experience started when his wife saw a neighbour beekeeping over the garden fence. He is now in charge of passing on new scientific knowledge to novices. “The key is to educate the average newcomer who’s interested in beekeeping to a higher standard,” he says.

This approach reassures research scientists. “Part of what’s happened with the decline of the bees is that the beekeepers who are training now are much more knowledgeable and know how to deal with the problems,” says Dr Osborne. As research results grow, the community will adjust their practice.

Back in Sussex, Professor Ratnieks scans the campus for forthcoming flowers. “In a couple of weeks, that bank will have dandelions on it,” he points out. “That’ll be good.” His foragers will soon be on the wing again, carefully scrutinised by the humans who are trying to help them to stick around. But he’s optimistic about their future. “Honeybees have been around for millions of years,” he says. “If I was going to back one species to go extinct, it would be the human, not the honeybee.”

Source: www.timesonline.co.uk/tol/news/science/eureka/article7112755.ece?token=null&offset=0&page=1