CRISTIANO MENEZES / EMBRAPA Sweet work: Melipona seminigra transports a grain of pollenCRISTIANO MENEZES / EMBRAPA
Humans have explored honeybee colonies since prehistoric times, but only in recent years have we learned that the importance of these insects goes well beyond making the powerful natural sweetener. “Actually, honey is a small sub-product when compared to the value of the pollination service provided by the bees, which corresponds to nearly 10% of the world’s agricultural production value,” said Vera Lúcia Imperatriz Fonseca, professor at the University of São Paulo (USP) during her lecture at the second meeting of the 2014 Biota-FAPESP Conference Cycle held in São Paulo on March 20, 2014. The biologist went on to say that by carrying pollen from one flower to the next, bees are able to increase plant fecundity and generate productivity gains in a variety of crops that corresponds to nearly 10% of the world’s agricultural production value.
Scientists estimate that in 2007, the total value of honey exported stood at US$1.5 billion. During the same year, the value of pollination ecosystem services throughout the world was calculated at US$212 billion, according to data collected by several studies and compiled in a book by Fonseca entitled “Polinizadores no Brasil: contribuição e perspectivas para a biodiversidade, uso sustentável, conservação e serviços ambientais” (Pollinators in Brazil: contribution and prospects for biodiversity, sustainable use, conservation and environmental services), one of the winners of the 2013 Jabuti Prize.
TOM WENSELEERS / UNIVERSITY OF LEUVENApis mellifera visits an orange blossomTOM WENSELEERS / UNIVERSITY OF LEUVEN
Plants and fruits whose total annual production is €100 billion are the principal foods that require insects for pollination. Next are the oilseed crops, stimulants (coffee and tea), almonds and spices. On average, the cultures that do not depend on insect pollination involve €151 billion per year, whereas those that do depend on pollination are valued at €761 billion.
“Nearly 75% of our food depends directly or indirectly on plants pollinated or improved by animal pollination. Of these, 35% depend solely on pollinators,” said Fonseca, who is currently a visiting professor at the Federal Rural University of the Semiarid Region (UFERSA) in the state of Rio Grande do Norte. In the rest of the cases, insects such as bees help to increase fruit quality and yield.
Recent studies have shown that even crops such as canola, pollinated by the wind, and soybean whose flowers are fertilized by their own pollen, produce between 20% to 40% more grains per hectare when colonies of bees of the species Apis mellifera are nearby or when the crops are planted alongside remaining areas of native vegetation.
Eduardo CesarBiologists Vera Fonseca, Kayna Agostini and Cláudia SilvaEduardo Cesar
“When jatai bees are used to pollinate strawberry plants in protected environments, there is a 70% reduction in the number of poorly formed fruit in some cultivars,” said Fonseca. Another crop that may benefit from pollination by bees in protected environments is the tomato plant, which needs bees, such as bumblebees of the genus Bombus, or stingless bees such as tiúba or mandaçaia bees (from the genus Melipona) that cause the flowers to vibrate in order to be fertilized. “In general, bees increase the production of seeds, improve the quality of the habitat, make agricultural systems more sustainable, bring great benefits to the environment, and promote other ecosystem services that allow preservation of the biodiversity and water resources,” Fonseca added.
Although the demand for pollination services performed by bees has been growing at the same rate as world agricultural production, the habitats favorable to maintaining these insects have been diminishing every year. Environmental changes are apparently behind the recent phenomenon that scientists have named colony collapse disorder. The syndrome involving the disappearance of the bees was first detected in 2007 in the Northern Hemisphere and is currently associated with the loss of approximately 30% of the colonies of Apis mellifera each year. As a result of this problem that also affects Europe and arrived in Brazil in 2011, farmers have had to import bees from other regions to promote agricultural pollination.
PATRICIA NUNES SILVA / PUC-RSA Melipona on an eggplant flowerPATRICIA NUNES SILVA / PUC-RS
“Renting a bee colony for pollination can cost up to US$200 in the United States because producers know that the profits generated by the service will be much higher. And there are not enough bees,” explained Fonseca. She went on to say that this is a global trend because we are increasingly planting crops that depend on bees for their production.
Among the factors identified as causes for the disappearance of the bees is the improper use of herbicides and pesticides, deforestation following the use of the soil for large monocultures, and the migration of colonies for agricultural pollination. “Pesticides, when they don’t kill bees, weaken them and reduce the time spent foraging (searching for food),” explained Fonseca.
These factors add up. When native vegetation is replaced by monoculture crops bees have to go increasingly farther in search of food because there are fewer types of flowers. The migration of colonies, in turn, could increase the competition for food among the species and foster the spread of disease.
This scenario tends to worsen with the arrival of a new villain: global climate change. The basis of the difficulty is that the pollinators, as well as the plants that maintain their colonies, have a geographical distribution radius that is influenced by temperature and rainfall.
SÍDIA WITTER / ZOOBOTANICAL FOUNDATION OF RIO GRANDE DO SUL 7 PATRICIA NUNES SILVA / PUC-RSA bumblebee (Bombus morio) collects nectar from a passion flowerSÍDIA WITTER / ZOOBOTANICAL FOUNDATION OF RIO GRANDE DO SUL 7 PATRICIA NUNES SILVA / PUC-RS
Predictions by the United Nations Intergovernmental Panel on Climate Change (IPCC) suggest that northeastern Brazil could experience a 4ºC increase in temperature over the next 50 years. According to Fonseca, this warming could cause a significant change in the areas in which bees occur. “We’ve performed species distribution modeling studies and studies that use pollen analysis of the food collected by the bees to learn which plants they are visiting,” she explained. These tools allowed them to map the use of floral resources and, with the help of the virtual flora and fungi herbaria available on the Internet, identify the current distribution and model the principal sources of food for the bees. “By cross-referencing the data, we can identify the most important natural areas to be rebuilt and preserved and plan a mitigation program so that, in 40 or 50 years, the bees will have a place to live,” explained the biologist.
Bee diet
Cláudia Inês da Silva, visiting professor from the Federal University of Ceará (UFC), has devoted herself to studying the dietary habits of bumblebees of the genus Xylocopa and other bees that are important for pollinating passion fruit for the purpose of preserving important natural areas for attracting and maintaining these insects. “We selected the passion fruit because it is of high economic importance to Brazil, which contributes more than 60% of the world’s production of passion fruit,” said Silva during the March conference.
The fruit is typically grown on family farms and experiences huge fluctuations in production, mainly due to handling and raw material costs. “And pollination has a direct influence on these production costs,” said the biologist. According to her, rural producers generally lack knowledge about the insects that visit the flowers of the passion fruit plant as well as about the biology of these plants and their reproductive systems, which are completely dependent upon pollination by bees.
“In the case of the passion fruit, not all bees are beneficial,” Silva explained. Some, such as Apis mellifera, are very small and only gather the nectar and the pollen but do not promote pollination. “It’s important to understand the needs of each crop and preserve the most appropriate pollinator,” said Silva.
A study conducted at the Federal University of Viçosa has estimated that in an area of just over two hectares of passion fruit crops, the services provided by carpenter bees (Xylocopa) reduce production costs by approximately R$ 33,000 per hectare every three years.
Despite the importance of the carpenter bees, they are often killed by the farmers, who consider them aggressive, Silva stated. “Because they think the carpenter bees are beetles,” said Silva, “they’re afraid that the bees will eat the flowers, destroy the crop and ruin the fences where they usually build their nests.”
In her doctoral studies at the Federal University of Uberlândia under the advisorship of Paulo Eugênio de Oliveira, Silva identified 112 species of plants used to nourish the carpenter bees. Some of the most important are considered by farmers to be weeds (species of the genera Senna and Solanum) and are often removed from the surroundings.
“Based on this study, we prepared a proposal to enrich and restore the plants that are important for attracting and maintaining these bees. Beginning with a study of the bees’ diet, we have planned a current and future scenario in order to identify potential areas for growing passion fruit,” the UFC biologist said. The information has helped her to compile the book “Manejo dos Polinizadores e Polinização de Maracujá” (Management of passion fruit pollinators and pollination) to be released with support from the Ministry of the Environment. The protocols she developed are being adopted in studies of crops such as strawberries, cashews, cacao and acerola.
Many systems
Bees are considered professional pollinators because they have body structures that are specialized for collecting and transporting pollen. But beetles, butterflies, moths, flies, small birds and bats also contribute to this ecosystem service, said biologist Kayna Agostini of the Federal University of São Carlos (UFSCar) at Araras, in her lecture. “All of the known pollination systems are found in Brazil, because the country lies in a predominantly tropical climate zone,” she noted. “Some of these systems are abiotic, as in the case of pollination by wind, but the great majority occur through biotic agents.”
According to Agostini, plant-animal interactions are largely mutualistic, in that both parties are benefited. But recent studies indicate that the rule does not apply in every case. She cites the example of the Brazilian Dutchman’s Pipe (Aristolochia gigantea). The flower of this plant tricks flies with its meat-like appearance and odor. When a fly attempts to deposit its eggs, it discovers the deception and tries to fly across the flower but becomes trapped. “Only after the pollen adheres to its body is the fly able to leave, without receiving any benefit from the interaction. Animals visit flowers in search of pollen, which is a source of protein, and sugar-rich nectar, as well as oils, scents and resins,” said the researcher in her Biota-FAPESP Education lecture.
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