Pumping bellows to create gentle puffs of smoke, Alfonso Cestelos Sanz fends off the ants attacking his beehive in a field overlooking Mexico City, before pulling out sticky racks of hexagon-shaped honeycomb amid clouds of irritated bees.
His face covered with the netting of his thick white suit to protect against stings, Cestelos explains how threats to bees in the megacity could jeopardise efforts to make it greener, as the insects fall victim to the same factors decimating rural bee populations - as well as urban sprawl. "Think of a grey place without any green spots - the urban stain. These buildings are eating away at the woods and parks so the bees don't have sources of food,” said Cestelos, whose bees buzz over 300 hectares (740 acres) of protected land in the city's southwest.
"Bees are important in cities as they pollinate plants which are helping clean the atmosphere,” said Cestelos, manager of Apicultura, which runs beekeeping workshops. Greening cities is touted by environmentalists and urban planners alike as a way to solve some of the major metropolitan challenges linked to the intensifying effects of climate change.
More trees, plants and green rooftops can absorb larger amounts of pollutants and carbon, which forms the main planet-warming gas, they say. Creating green spaces in cities can cool them and curb the impact of heatwave temperature spikes, while helping soak up heavy rainfall to cut flooding risk, say experts.
But in urban areas where bees are at risk, that could be a harder task. Under attack from a poorly understood phenomenon known as colony collapse disorder, bee populations have declined sharply around the world.
Pesticide use, disease and mites, as well as habitat loss, are largely blamed for their decline. The effects may be far reaching. A global assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services last year showed up to $577 billion of world food output depended on bees and other pollinators.
Urban beekeeping is on the rise in cities such as London and New York where homeowners, companies and restaurants are setting up rooftop hives that each house thousands of bees. But strict rules in densely packed Mexico City about the location of hives restrict them mainly to the city fringes.
As the city continues to expand, reducing green areas, beekeepers have less space to work, said Adriana Pena Veliz, a vet who advises Efecto Colmena (Beehive Effect), which rescues and relocates bee swarms.
"The bees are starting to lose their habitat,” she said. Mexico ranks as one of the world's biggest honey producers, churning out more than 55,000 tonnes last year from over 40,000 beekeepers who tend about 2 million hives around the country. It wants to sign up more producers - but its bees are under pressure both in rural honey-producing areas and cities.
Figures from the agriculture ministry (SAGARPA) show the number of hives in Mexico City, as well as honey production, dropped by about 17 per cent between 2006 and 2015. Beekeepers, however, estimate that populations in the capital have fallen by up to 30 per cent in recent years, said Apicultura's Cestelos. The city now has some 200 beekeepers with about 5,000 hives, according to official data.
But Pena said that is a small number given a single commercial producer in a rural area might run hundreds of hives. Working with the already stretched emergency services to persuade them not to exterminate bees when called out by residents, some of whom fear they might be under attack from aggressive Africanised "killer bees”, Efecto Colmena rescues colonies on the loose by luring them into special boxes and relocating them to hives outside the city.
At a suburban Mexico City house where beehives sit in long, damp grass, Pena said the organisation wants to train the city's firemen to handle the sensitive insects correctly and stop swarms getting out of control.
"We're trying to change how bees are treated in the city,” said Jeronimo Quiroz Fernandez-Macgregor, Efecto Colmena’s co-founder. "If you have a swarm at your house and call the firemen, they have a protocol of extermination, mostly with water and soap - the soap goes into (the bees') respiratory systems and they choke to death.” With many bees fleeing the fields due to the use of agrochemicals, they head to cities where residents don't want them and they are often killed, he added.
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Helping boost bee populations is as simple as planting flowers in pots on the window sills of Mexico City's millions of apartments, growing more fruit trees, and reducing pesticide use in gardens and parks, said experts.
Better education about bees is also crucial, said Cestelos, whose organisation holds workshops for children. He has found sponsorship from a restaurant and food company for some of the hives kept at the Ectagono community project, which promotes urban farming and watershed conservation on its sprawling site in the city's southwest.
Noah Wilson-Rich, whose Boston-based The Best Bees Company works with beekeepers in U.S. cities, said urban bees face the same problems as their country cousins, but analysis of honey samples show how healthy city bees can benefit from habitat diversity and a broad range of plant species.
"When we have bees around, the whole plant ecosystem of a city or urban environment can replicate - that's the role of pollinators,” said Wilson-Rich by telephone. "The cities are really the next farms,” he added. "It's the next frontier for how we produce food, and we have to be smarter about these spaces if we're going to survive with a growing population." - Thomson Reuters Foundation