From the Internet:
June 19, 2013
Will we have fruit in a future without bees?
A photo has been circulating this week that suggests that this is what our grocery stores will look like without bees:
Whole Foods Produce Dept.
Whole Foods Market produce department without items dependent on pollinator populations. (PRNewsFoto/Whole Foods Market)
Is that true? Is this our life without bees, come the future Beepocalypse?
A fruit is, essentially, a delicious plant ovary with embryos (seeds) inside. It's how plants reproduce. Bees and other pollinators serve as plant sexual surrogates by spreading pollen (plant sperm!) around to flower ovaries. A fruit tree flower has to be pollinated to "set fruit" or begin to create the plant embryos that will become apples.
Some fruits are self-pollinating, and can fertilize themselves without any bees involved. The Navel Oranges seen in the photo above are a good example of a fruit that can self-pollinate. Most fruit trees-pears and apples in particular-are self-sterile for their own pollen. If you plant all Royal Delicious apples, for example, you won't get fruit, with or without bees. Just as we don't often marry our cousins, apple and pear trees require cross-pollination with "pollinizer varieties" that are not closely related to produce a full crop of fruit.
hand pollination in china
Hand Pollination; Image from International Centre for Integrated Mountain Development, Nepal
So it's certainly true that loss of bees and other pollinating insects would limit our fruit choices. But what would happen if bees went away all together?
Actually, we already know what raising fruit without honey bees looks like. In a remote area in China, humans pollinate 100% of fruit trees by hand. Armed with pollen-loaded paintbrushes and cigarette filters, people swarm around pear and apple trees in spring, replacing bees as pollinators. The reason why they do that, though, is more complex than just "the bees died."
There's a fair amount of data about the history of human pollination, and the reason it happens in China has as much to do with economics and apple biology as it does with missing bees. In the early 1990s, farmers of marginal lands in the Hindu Kush Himalayan region-an area spanning parts of Nepal, China, Pakistan, and India-realized that apples could be a major cash crop. Their land was mountainous and hard to farm, so tree fruits were ideally suited to the region. A major shift occurred from subsistence farming to fruit crops. The payoffs were large-in some areas, farmers quadrupled their income. Now they had cash on hand to send kids to school and build roads. Quality of life improved.
With that early success, farmers found that certain varieties of apples and pears sold better than others. As new orchards went in, more and more of the same cultivars of apples were planted. And that is when things started to go wrong.
Clearing marginal forested lands for more agriculture destroyed nesting and food resources native pollinator species needed. The problem with insects as commercial pollinators is that they can't just appear for 2 weeks, pollinate your plants, and disappear. They have to have something to eat the rest of the year, and a place to live. Clearing mountain forests got rid of habitat that pollinators needed.
Farmers planting new trees in their orchards made a logical economic choice: plant more trees that make marketable fruit. The consequences of that choice, though, were that fruit set was poor. Most of the trees they planted were the same variety, so were self-sterile.
So farmers added a few of what are called "pollinizer" trees-trees that serve as pollen donors. Pollinizer varieties usually don't have pretty fruit, which means that farmers are giving up potential income if they plant them. The recommended mix of fruiting trees and pollinizer trees in orchards is 70:30. In most fruit orchards in this region, less than 10% of the trees were pollinizer varieties. Worse, you can't just randomly pick two different kinds of apple or pear trees and have them be cross-fertile. (This compatibility matrix gives you a sense of just how complex choosing two pear cultivars to grow can be.) Your pollinizer variety also must bloom at the same time as your fruit variety-pollen needs to be used while it is fresh, and can't be stored. So even with plenty of bees, fruit production was very low, and in some areas crops failed completely.
Another perfectly sensible economic decision made by farmers was to spray pesticides often to have better looking fruit, which commanded a better price. A perception that the problem with poor fruit production was caused by pest insects also encouraged more spraying. Just as in cultivar selection, this had unforeseen biological consequences. Poor pollination due to pollen incompatibility was made worse by killing off pollinating insects.
In 1999, the problem of poor fruit set was widespread throughout the Hindu Kush regions of Nepal, China, Pakistan, and India. Hand pollination was widely practiced through this region. However, by 2011, only apple growers in the Maoxian region of China were still hand pollinating. What was different about China that made hand pollination persist?
In Nepal, India, and Pakistan, the government and NGOs provided support to help promote using native pollinator species, as well as provided training and education about managing pollination. Planting of native host trees that provided nectar to support colonies through the harvest year was encouraged. Bees are now an important part of local economies, and hand pollination is now rare.
In China, officials promoted and offered training in hand pollination, rather than offering information about native pollinators. That's not the only reason hand pollination persisted, though-100% of apple crops in the Maoxian region are pollinated by hand because it makes economic sense. By using humans as pollinators, the number of pollenizer trees that have to be planted can be minimized, and valuable land isn't used up for non-productive trees. Fruit set is also much higher with human pollinators-every flower is fully pollinated and can become fruit. A person can pollinate 5-10 trees a day, depending on the size of the trees. Farmers pay their human pollinators US $12-19/person/day. The cost of renting a bee colony for pollination in 2010 was US $46.88/day.
Why are bees so expensive in Maoxian? Honey bees are still present-up to 50% of the fruit farmers surveyed in the Maoxian region in 2011 also kept honey bees! Bees are still viewed as primarily a honey-producing species in this region, so the connection between bees and pollination is not strong. Farmers in this region of China are uninformed about the effects of pesticides on bees-half of apple farmers surveyed did not know that pesticides would kill bees. The Maoxian region also sprays pesticides more often than other regions where pollinators have recovered. Most Maoxian beekeepers will not rent their hives to orchards, since the pesticide sprays continue during bloom season and they risk losing their entire hive.
One last additional factor is making things difficult for farmers: Global Climate Change. Frequent rains, low temperatures, and cloudy weather affect the number of days that plants flower and the times that pollinators can fly. Changes in flowering time also means that fruit trees and their local pollinators may not be in sync, which makes a mismatch between pollinator and plant timing more likely in an already strained system. Humans are more effective pollinators than insects under these adverse conditions.
What can North Americans learn from China's pollination failure?
The story of hand pollination in China illustrates what a failure to understand natural ecosystem services looks like. Ecosystem services are things the earth does for us for free: Oxygen is produced; water is filtered; and plants are pollinated. When parts of an ecosystem are removed, it stops functioning the way it has in the past.
Problems with bees, agriculture, and pollination are deeply related to issues of habitat loss, global warming, and basic plant biology. Pesticides are a problem in bee deaths-for all bees, not just honey bees. But just getting rid of all pesticides will not solve our bee problems, and pesticides are only part of the story of human pollination.
In the most recent US honey bee reports from the winter of 2012-2013, 31% of hives failed in the United States. It wasn't Colony Collapse Disorder or poisoning that was the problem, though-most of the bees starved. A summer of drought that reduced honey storage combined with odd winter weather stresses bee hives. It doesn't help that corn, soybeans, and golf courses are not nutritious food sources for honey bees. We also know that incredible losses in native bee diversity are happening-in one study, 50% of Midwestern native bee species disappeared over a 100 year period.
Is China's experience a picture of our future without bees? Probably not. But preserving our pollinators and pollinator habitat will be critical to keeping our food choices diverse. This Pollinator Week, consider planting some food for bees, or setting aside some nesting space for native bees. Check out this huge resource center for North American plant lists, nesting guides, and more.
•Burkle L.A., Marlin J.C. & Knight T.M. (2013). Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence, and Function, Science, 339 (6127) 1611-1615. DOI: 10.1126/science.1232728
•Garibaldi L.A., Steffan-Dewenter I., Winfree R., Aizen M.A., Bommarco R., Cunningham S.A., Kremen C., Carvalheiro L.G., Harder L.D. & Afik O. & (2013). Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance, Science, 339 (6127) 1608-1611. DOI: 10.1126/science.1230200
•Partap U. & Ya T. (2012). The Human Pollinators of Fruit Crops in Maoxian County, Sichuan, China, Mountain Research and Development, 32 (2) 176-186. DOI: 10.1659/MRD-JOURNAL-D-11-00108.1
•Partap U. (2010). Innovations in revival strategies for declining pollinators with particular reference to the indigenous honey bees: Experiences of ICIMOD's initiatives in the Hindu Rush-Himalayan region, Pest Management and Economic Zoology, 18 (1) 85-95.
•Tang Ya, Xie Jia-sui, & Chen Keming (2001). Hand pollination of pears and its implications for biodiversity conservation and environmental protection - A case study from Hanyuan County, Sichuan Province, China, FAO Case studies on pollinators and pollination.
•Warning Signals from the Apple Valleys of the Hindu Kush-Himalayas: Productivity Concerns and Pollination Problems (2002). Kathmandu, Nepal: International Centre for Integrated Mountain Development. 116pp.
•Case Study #10: Cash Crop Farming in the Himalayas.
It's National Pollinator Week!
It's National Pollinator Week!
It's National Pollinator Week!
In "Ask an Entomologist"