Feature: Protecting the pollinators part 1 - bees and ecology
29 March 2011. By Chrissie Giles
We all know that bees make honey, but they do much more for the food we eat. Bees and other insects, including wasps and hoverflies, pollinate plants. By transferring pollen from the male parts of flowers to the female parts, they're a vital part of the process that eventually leads to fruit, nut and seed production.
For some crops, such as melons, no pollinators means no fruit. For others, no pollinators means a lesser harvest. This widespread role of insects in food production is reflected in insect pollinators' economic value - estimated to be around €153 billion (£130bn) globally in 2005.[1]
But pollinators are under threat. Research published in 2006 indicates that the diversity of wild bees - a key pollinator group - has declined severely since the 1980s.[2] Another major pollinator, honeybees, are prone to a number of diseases. The mite Varroa destructor, for example, carries viruses that can quickly destroy entire colonies, and has spread almost completely around the world in the last 30 years.
Unlike some other major ecological challenges of the past, such as the decline in peregrines caused by the use of DDT in the 1950s and 1960s, the problems with pollinators could be numerous. "There's likely a smorgasbord of problems," says Professor Jane Memmott from the University of Bristol, a lead investigator on one of the projects funded by the Initiative. "And they probably interact in different ways too - if bees are not properly fed, then they're more likely to catch diseases, and so on."
The nine projects funded through the Insect Pollinators Initiative are setting out to understand these threats better. Five of these projects, designed to boost our understanding of bees and their ecology, are detailed below. Find out about the other four projects in the second of this pair of features.
Which insects are pollinating our crops?
When Dr Koos Biesmeijer, a Research Fellow at the University of Leeds, begins his lecture on the decline of pollinators, he does so with a cappuccino in hand. "The ingredients of a fancy coffee - coffee, cocoa, vanilla, nuts - rely on insect pollinators such as bees and wasps to grow," he explains, emphasising that some two-thirds of the foodstuffs that we eat benefit from insect pollination.
Research published by Koos and colleagues in 2006[2] showed that the diversity of wild bees has declined severely. Combined with the fact that honeybees are under threat from many diseases, it becomes clear, as Koos puts it, that both methods we rely on for pollinating our crops are in trouble.
"There’s a lot of discussion about how a fall in pollinator numbers will affect crop prices - but no one really knows for sure if it will or not," he says. "That's why we're trying to find out which insects are pollinating our crops, and to what extent more pollinators would increase yield."
His team is focusing on plants that represent four major crop groups: apples, strawberries, field beans and oilseed rape, on farms across England and Scotland.
"We'll select farms in different places, get a good idea of the pollinators available there and see if the farmers have crop deficits or not," says Koos. The researchers are using cages that allow them to introduce different pollinators to a particular plant, to assess different pollinators' contributions. The team will also see whether a wider range of pollinator species helps provide greater levels of pollination.
Another aspect of the project is modelling. The researchers will use information on honeybees, wild pollinators and crop pollination to model where pollination may be lacking, and to explore the potential effects of climate change on landscapes and crop production in the UK, to identify what we need to do to minimise these effects.
Is the fall in bee diversity linked to the fall in wildflowers?
Along with Koos, Professor Bill Kunin at the University of Leeds was a co-author on a 2006 'Science' paper showing that bee diversity has been dropping in the UK, and that wildflowers that depend on them for pollination have been declining in recent years as well.
"It seems likely that a fall in bee diversity and a fall in flower number are linked, but even that is seat-of-the-pants intuition," he says. "There's precious little evidence at the moment."
To understand more, Bill and colleagues are looking at how the abundance of insect-pollinated crops and wildflowers correlates with the diversity of bee species and the number of bees and other pollinators in a given area.
If researchers knew which flowers were where in the landscape, they would be able to work out how well proposed schemes to boost bee diversity might work. "It might be that you get a bigger 'hit' in floral resources by altering the way we manage road verges, or changing grazing patterns," says Bill.
The findings could have important implications for agriculture. "If it turns out that pollinator abundance and diversity isn't connected to the number of flowers present, then that would already undermine the whole notion that taxpayers should be paying farmers to plant flowers," he explains.
"It might be what's really causing pollinator decline is pesticide use - if that's the case, we ought to be subsiding people to use fewer pesticides and forget about planting margins full of flowers." Other potential causes include an increase in the use of fertilisers and the loss of natural habitats.
This project is looking only at rural areas, as cities, Bill laughs, are too complicated and messy. Instead, a team led by Jane Memmott (see below) will be tackling pollinators in urban areas.
How are pollinators faring in urban habitats?
"There's no systematic study that tells us how pollinators are doing in urban habitats," says Professor Jane Memmott from the University of Bristol. "There are hints, nuggets of information, but most people don't use the same sampling techniques in towns and cities as they would in the countryside so we don't have the data to compare the different habitats properly."
Until now, that is. Jane and her colleagues have been looking at the network of interactions between plants and the birds, insects and other animals that visit flowers - a study they are expanding as part of the project funded through the Insect Pollinators Initiative.
"We want to find out where pollinator diversity is in the UK - how do cities rank compared to the countryside and nature reserves?" says Jane. Her team is sampling cities, farms and nature reserves to make the first rigorous comparison of pollinator diversity and abundance in the UK. Once this stage is complete, they will home in on four cities - Bristol, Reading, Leeds and Edinburgh - for a detailed look at these urban habitats. "We'll divide the cities into different components - gardens, nature reserves, roadside verges - and work out which parts are best for wildlife." And the team's approach is community-wide, that is, concerned with everything that visits the flower, from bees to flies, beetles to butterflies.
"My gut feeling is that gardens are good," says Jane, "But that weedy wasteland corners in urban areas can be really beneficial for pollinators and that gardens are only a small part of the story."
The researchers will model different combinations to work out what combination of land use is best to keep pollinators healthy and happy in a city. "How can we improve life for pollinators in cities?" asks Jane, explaining that they will take the idea of environmental stewardship projects on farms and add plants that provide pollen and nectar into cities.
As with all nine projects funded through this Initiative, the researchers hope to have an impact on how pollinators are managed in the future. "Right from the beginning we're working closely with people from wildlife trusts and the councils' ecology teams," says Jane. At the end of the project the researchers will invite people from every city council and every wildlife trust in the UK to Bristol to hear about what"s been learned from the project, and how they can use these findings in their own jobs.
How can we make the countryside better for bumblebees?
Like Jane, Dr Claire Carvell from the NERC Centre for Ecology and Hydrology in Oxfordshire is also concerned with managing land better for pollinators. Claire and her colleagues are exploring how bumblebees live in the wild.
The need to manage the countryside so that bees can thrive is more pressing than ever, as bumblebee numbers have fallen seriously in recent years. It is thought that part of the reason is a dramatic decline in the plant species that the bees feed on.
"Although we know a fair bit about bumblebees and their ecology, there are quite a few things we don't know," Claire explains. For example, the researchers want to understand how the bumblebees from a nest use the landscape around them - but locating nests in the wild is hard. "Often, we find nests by complete chance. Other times a badger has beaten us to it, leaving a disturbed colony that may not be behaving as it was before."
Claire's team aims to answer a series of questions using a new combination of molecular and modelling approaches: What determines where queens nest? How far do worker bees fly to forage? How does the structure and quality of the landscape affect these behaviours?
Bumblebee colonies exist on an annual cycle, which means that if a nest is successful, once a year it will produce a number of new queens that will go out into the landscape to make their own nests. The workers, males and old queen die. By collecting DNA from queen and worker bumblebees in particular areas, Claire and her team will be able to tell how related the bees are, and estimate how far they may have dispersed or flown from their maternal nest. To collect DNA, they will use a technique that involves clipping the tip of the bee's mid-leg, which, Claire explains, is a bit like trimming a toenail.
"The hypothesis is that, in a poor-quality landscape [for example, one in which foraging plants are limited], workers are likely to have to fly further to find food and, where a nest is successful, the queens are more likely to have to disperse further," says Claire. "There's also a lot we don't know about levels of genetic diversity within populations, which we hope to find out."
Are British bees getting the right diet?
Like doing the grocery shopping for your family, foraging worker bees have to pick food that is right not only for them but also for those back home. The bee's shopping list is simpler, though: pollen is the main source of protein and nectar the main source of carbohydrate.
"How worker bees choose food is not well understood," says Dr Geraldine Wright from Newcastle University. She is investigating bee nutrition, and how a bee's nutritional state affects how it forages. "We're looking to find out if bees need to forage from one or several different species to achieve their optimal carbohydrate-to-protein ratio."
She is working with Dr Annie Borland, a plant physiologist at Newcastle, and Dr Phil Stevenson, from the Royal Botanic Gardens at Kew, to measure the nutritional content of nectar and pollen that bees get from different agricultural, horticultural and native UK species.
Geraldine says: "One thing that's emerging from the work of our collaborator, Professor Sue Nicolson at the University of Pretoria in South Africa, is that workers don't survive well on a high-protein diet, but this is in fact what the brood [the immature bees] need. It will be really interesting to find out how much the honeybee has to disregard its own nutritional state while it's foraging."
The data will be put on a freely available online database. This should help anyone interested plant the right plants to provide a balanced diet for their bees, and researchers are developing artificial bee foods that could help to build up colonies in the spring.
While bee nutrition is the focus of the project, research by Geraldine's laboratory is mainly around understanding the mechanisms of learning and memory. She and her colleagues have been using the honeybee as a model for some time, and are bringing that knowledge to their new work.
"We don't know a lot about nutrition and how it influences learning and memory. This project will allow us to understand exactly what honeybees and bumblebees need, in terms of pollen and nectar, but also how their foraging can feed back on to what they do when they're learning." For example, she says, if a bee is low on protein in their diet, are they more likely to learn to associate a floral scent with an amino acid (which proteins are made of) than a sugar?
A very active area of research in the field of learning is how much nutritional feedback influences learning, and how much your physiological state may influence what you learn during a repetitive learning task. With Professor Sharoni Shafir at the Hebrew University, Israel, Geraldine will be investigating how bees weight rewards, or, as she puts it: "We're going to look at how nutrition affects the cognitive-behavioural decisions that forager bees have to make when they're out doing the shopping."
Image: A bumblebee (Bombus pascuorum) foraging on red clover. Credit: © Claire Carvell, Centre for Ecology and Hydrology.
References
1. Gallai N et al.
Economic valuation of the vulnerability of world agriculture confronted with pollinator decline. Ecological Economics 2009;68(3):810-21.
2. Biesmeijer JC et al.
Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands. Science 2006;313(5785):351-4.
- Koos Biesmeijer is working with colleagues Dr Mette Termansen and Dr Andy Challinor at the University of Leeds, Dr Giles Budge at the National Bee Unit, Nigel Boatman at the Food and Environment Research Agency and Dr Simon Potts at the University of Reading.
- Bill Kunin is working with Dr Koos Biesmeijer, Dr Andy Bulpitt and Dr Steve Compton at the University of Leeds, Prof. Jane Memmott at the University of Bristol, Dr Nigel Boatman, Dr Phil Northing and Dr Giles Budge at the Food and Environment Research Agency, Dr Dan Morton and Dr Simon Smart at the NERC Centre for Ecology and Hydrology, and Dr Simon Potts and Mr Stuart Roberts at the University of Reading.
- Jane Memmott is working with Dr Graham Stone at the University of Edinburgh, Dr Koos Biesmeijer and Prof. Bill Kunin at the University of Leeds, and Dr Simon Potts at the University of Reading.
- Claire Carvell is working with colleague Matt Heard at the Centre for Ecology and Hydrology, Prof. Andrew Bourke at the University of East Anglia, and Dr Bill Jordan and Dr Seirian Sumner at the Institute of Zoology, Zoological Society of London.
- Geraldine Wright is working with Dr Phil Stevenson at the Royal Botanic Gardens, Kew, Dr Annie Borland at Newcastle University, Prof. Sue Nicolson at the University of Pretoria, Prof. Sharoni Shafir at the Hebrew University of Jerusalem, and Prof. Steve Simpson at the University of Sydney.
The Insect Pollinators Initiative is supported by the Biotechnology and Biological Sciences Research Council, the Department for Environment, Food and Rural Affairs, the Natural Environment Research Council, the Scottish Government and the Wellcome Trust, under the auspices of the Living With Environmental Change partnership.
