Concrete jungles: the surprisingly rich biodiversity of big cities

They're home to packed streets, skyscrapers and smog but big cities need to plan for plants and animals too

Can cities really become home to a large variety of fauna and flora? Doesn't the wild world hate cement? The concept of biodiversity may seem to contradict the nature of cities, but scientists, designers and architects are working on urban development models that harmonize with the natural world.

The world is increasingly urban. If current trends continue, the metropolitan area of Bogotá, for example, will triple between 2000 and 2030, and the city's population will double, from 3 million to almost 5 million.

Globally, this urban expansion will use up both space and natural resources, especially water and farming land. It will happen more in regions with fewer economic capabilities and faster in regions with more biodiversity, as a 2012 report on biodiversity and cities concluded. This should not surprise us, as areas of rich biodiversity are precisely those that have always attracted human settlements and fomented trade.

The evidence about the presence of a wealth of fauna and flora in large cities may come as a surprise. More than 50% of flower species in Belgium are in Brussels, and Warsaw is home to 65% of all bird species in Poland. A study of 61 gardens in Sheffield, England, found 4,000 types of invertebrates, 80 types of lichens and more than 1,000 plants.

There are significant nature reserves in cities such as Mumbai, Stockholm, Nairobi, Cape Town and Tucson, Arizona, all of which make crucial contributions to biodiversity in those cities.

story_article_left1

These spaces improve the health and well-being of city residents by cutting noise and air pollution. "They are not so much complementary and secondary as vital to cultural activities, physical and mental health and the identity of a place," says María Angélica Mejía of Bogotá's Humboldt Institute.

In Sacramento, California, park joggers under 65 years old typically spend $250 less on medicines than people who don't exercise. Other studies show that proximity to trees can reduce child asthma and allergies.

Where there is carbon, plant green

Cities are currently thought to emit 70% of all greenhouse gases — which makes urban green spaces, whether they be parks or roof gardens, vital in mitigating climate change and storing carbon. These are the "soft infrastructures" that regulate the microclimate — the weather immediately around them — filter rainwater and absorb smog and excess dust. A study for the UK found that a 10% increase in city green cover reduced temperatures by 3% to 4%, which in turn reduced the use of air conditioning.

Current legal frameworks for protecting biodiversity include the UN Convention on Biological Diversity signed by 193 parties in 1993, and Colombia's own National Biodiversity Policy, adapted for Bogotá and Medellín, though only the latter has developed an action plan to implement its provisions, initially in the form of pilot projects.

Luis Germán Naranjo, the conservation chief for the World Wildlife Fund in Colombia, cites the country's isolated interventions to rescue biodiversity, such as saving Bogotá's wetlands and revitalizing the banks of the Sinú River in Montería. But he adds that "management of biodiversity in Colombian cities is ever precarious. Parks, for example, are seen as recreational spaces, not ecosystems that improve air quality or as habitats for plant and animal species."

story_article_right2

Conservation International's Patricia Bejarano says Colombia has barely begun to make the link between cities and biodiversity. "For a long time nobody paid attention in city planning to issues of biodiversity and its benefits. Now environmental problems have become more serious and more relevant around the world," she says. "Cities like Bogotá, Medellín and most recently Montería have made some advances in recovering ecosystems and their regional surroundings, and this has been through linking the environment with development plans."

City development and biodiversity must now be systematically linked, she suggests. She cites examples of the ravines that have been restored in Bogotá to become tourist destinations that are also appreciated by the capital's residents. "It is interesting how in Bogotá, the recovery of certain gorges has allowed citizens to understand the real importance of ecosystems, not just for preventing or mitigating risks but to improve air quality," she says. "And the proof of this is that most people have begun opposing building projects in the city's eastern mountains."

Cities must change their perspectives on development, neither halting construction because of biodiversity, says Humboldt's María Angélica Mejía, "nor abandoning everything that is green."

--2015 New York Times News Service