A birdhouse hangs from a tree branch near traffic signs in central Madrid.
One of more than 100 birdhouses that Madrid's city government has installed around the city Madrid City Council

Since 2015, Madrid’s government has been trying to increase the city’s biodiversity. Hundreds of birdhouses and “insect hotels” around the city seem to be working.

MADRID—In Spain’s capital, urban agriculturalists are busy counting birds, butterflies, and other fauna and flora as the city government prepares to release its first strategic plan for biodiversity, presented to the media on June 19th and expected to be approved next week. Burgeoning wildlife is seen as an indicator of Madrid’s environmental health, and a reason to continue the measures that the city has been practicing for the past two years.

The flagship project of Madrid’s quest for biodiversity is centered on the Manzanares River, a modest stream that flows across the city, and that has suffered from decades of bad ideas. In the 1950s, urban planners built seven floodgates along the river to raise the water level so it would look more like the prominent rivers of London, Rome, and Paris.

Lofty expectations soon gave way to a 130-foot-wide, 6.5-foot-deep, greenish—sometimes stinky—still-water plate along a four-plus-mile channel. The planners hadn’t quite realized that rivers, well, just need to flow.

Madrid’s ring road, M-30, built along the riverside in the mid-1970s, was the most recent and possibly worst urban-planning decision inflicted on the river. It split the city like a knife hack, rather than connecting the urban center with outer areas. But an ambitious project begun in the late 1990s relocated the roads to tunnels underneath the riverbed and developed the ground above, resulting in the Manzanares Linear Park, inaugurated in 2011.

People lounging along the free-flowing Manzanares River in 2017. (Susana Vera/Reuters)

Two years ago, the city opened the river’s floodgates, allowing the river to follow its course and recover its original appearance. Now, the Manzanares is no more than about 11 inches deep, but life is booming on the river banks, and the sandy islands of sediment between the natural meanders are covered in bulrushes, reeds, and young willows.

Since the water started flowing, bird diversity has doubled in the area, with more than 50 different species currently finding shelter and food on the river banks. The population of mallards has risen from 15 in 2016 to 130, and common moorhens, egrets, little ringed plovers, and grey herons flutter around the thick vegetation. There are also swallows, kingfishers, night herons, blue tits, great tits, sparrows, common chiffchaffs, and European robins.

Madrid’s new approach to wildlife came about via its Natural Plan for Climate Change Adaptation and Mitigation, introduced in 2016 after a leftist citizens’ party, Ahora Madrid, took over Madrid City Council in coalition with the Socialist Party in 2015. The Natural Plan included restoring the Manzanares River; installing green roofs, and expanding urban farming, among other measures. The city’s environment and mobility department is directing it all, including a plan to improve air quality by restricting traffic in the city center beginning November 2019.

“That’s a goldfinch,” said Rafael Ruiz, head of the environmental education division of the environment and mobility department, as he points at a tiny brown and yellow bird perched on top of a thistle bud. Some 5,000 plants and trees have been planted along the river’s course, but the goldfinch has chosen thistle that grew wild on the riverside. “The Latin name of the goldfinch refers to the thistle. He traditionally feeds on its seeds,” Ruiz said. “These plants that we normally call weeds are actually the biggest reserves of biodiversity we can find in the city.”

Western cities have seen a sharp decline in bird life over the past 20 years. In Spain, the numbers of three well-adapted species—the house sparrow, the swallow, and the common swift—have dropped by 12.5, 30, and 33 percent respectively, according to data released by the Spanish Society of Ornithology.

To encourage biodiversity, the city is allowing grass in parks and green zones to grow taller, restricting the use of pesticides, and sparing spontaneous vegetation, at least until the breeding season is over. That means more seeds, fruit, and bugs for the urban fauna. The recipe appears to be working.

The increased use of glass and concrete for urban buildings instead of brick has meant fewer holes in buildings where birds can nest. In response to this, the city council installed more than 100 wooden birdhouses in 2017 and is adding another 165 this year—homes for sparrows, blue tits, great tits, and scops owls, to counteract their loss of habitat.

“The sparrow is very human-dependent, and as human cities change, its habitat changes too,” said Beatriz Sanchez, a researcher at the urban biodiversity program of the Spanish Society of Ornithology. Recent research by Madrid Complutense University showed higher levels of free-radical damage linked to air pollution and poor diets in house sparrows compared to their country cousins. Shrinking urban birdlife seems to be linked to a sharp decline in insect diversity and population. Studies have found that house-sparrow mortality is correlated with a shortage of aphids in urban areas.

“Insects seem to be disappearing in the Western world and, most likely, herbicides are to blame,” said Santiago Soria, a technical advisor to Madrid’s parks and botanical gardens department. As she spoke, Soria was standing under a holm oak tree at Madrid’s Casa de Campo Park, a large urban forest where rabbits, wild boars, and more than 200 different insect species find shelter. “Here, we don’t use pesticides,” Soria said. “Only occasionally against the pine processionary [a destructive moth], and we don’t remove the primary vegetation, such as herbs and weeds, and that has favored a healthy insect population. We need a lot of them."

The butterfly nursery at Casa de Campo (Jaime Velazquez)

A butterfly nursery in Casa de Campo breeds 15 different species for educational purposes, and the specimens are then released in the park. That adds to the 210 “insect hotels” located in schoolyard gardens and communal gardens across the city to ensure bug supply for pollination and enough food or the urban birdlife.

“In Madrid, we have always taken care of our trees and gardens, but until now we had never introduced a biodiversity perspective in the design of our green areas,” said Antonio Morcillo, Madrid’s deputy director for conservation of green areas and urban trees, of the recently approved plan. “Sometimes, small actions can bring incredible results.”

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