Cities have hardly been heralded as bastions of human health. In the USA, rates of childhood asthma have increased by 50 percent between 1980 and 2000, with the highest rates reported in poor urban communities.
In New York City, asthma is the leading cause of hospital admission among children under age 15.While these statistics are discouraging, at the same time mounting research has shown a connection between human health and cities that are rich in nature.
The ecosystem services that nature delivers, including the supply of food, fresh water, clean air, and medicines, the regulation of climate, floods, and diseases, and the provision of recreational, aesthetic, and spiritual benefits all contribute significantly to human well-being.
Opportunities for improved health
To investigate the impact of urban nature on childhood asthma in New York City, researchers at Columbia University conducted a study on the correlation between the number of neighborhood street trees and incidence of the disease.
Results showed that as the number of trees increased, prevalence of childhood asthma declined. This trend persisted even after data was adjusted for sociodemographics, population density, and proximity to pollution sources.
Furthermore, it was shown that adding an additional 343 trees per square kilometer decreased the asthma rate by as much as 24-29 percent among children ages 4 and 5.
The New York City study is not alone in demonstrating the benefits of nature to health; researchers are finding corroborating evidence across the globe. A recent study from Finland suggests that lack of exposure to a "natural environment" and certain bacteria could be resulting in more urban dwellers developing allergies and asthma.
In a Scottish study, researchers demonstrated a link between the lack of green spaces and higher stress levels among people living in “deprived" urban areas.
"There is growing international recognition of the vital links between human health and nature," says Stockholm Resilience Centre Professor Thomas Elmqvist.
"Biodiversity can be considered the foundation of human health."Elmqvist is leading the Cities and Biodiversity Outlook (CBO), an assessment of the links between urbanization, biodiversity, and ecosystem services, organised by the UN Secretariat Convention on Biological Diversity (CBD).
Future foundation for better health
The work on trees and New York City asthma is just one example documented in the CBO, which seeks not only to document scientific trends, but also to deliver key messages on the conservation and the sustainable use of natural resources to a crucial audience: decision-makers and planners.
"If current trends continue, by 2030 more than half the world's population will be living in cities," Elmqvist explains.
"Cities will thus be where the majority of the world's people will benefit from biodiversity, and they can also be the future foundation for better global health."
Actions for cities
A variety of cities across the world are heeding the call for enhancing biodiversity and ecosystems function, and many others could follow suit. New programmes that are being developed could be adapted for application to other urban locations.
The "Healthy Parks, Healthy People" initiative was launched by in 2000 by the park management agency of the State Government of Victoria, Australia, in order to emphasize the value of visiting parks and natural open spaces for the benefits they provide as healthy places for body, mind, and soul.
As it gained momentum, the programme served as springboard to a partnership with a national health insurance provider, which is now funding public activities to encourage people to increase their physical activity by visiting and engaging in activities in parks. The Healthy Parks, Healthy People programme has now been expanded to a number of other countries, including Nepal and the USA.
In New York City, where the challenges of childhood asthma still loom, there is also opportunity and hope — the MillionTreesNYC initiative is harnessing both public-private sectors to plant a million new trees in the city by 2017. The project will provide immediate greening to more streets, and offer further chance to study biodiversity's benefits for health.
Conserve and use it wisely
These are precisely the type of practical examples that Professor Elmqvist hopes to showcase in the Cities and Biodiversity Outlook.
"Cities that include open or green space and diverse natural ecosystem areas are not only more sustainable—they also encourage healthier lifestyles, strengthen our appreciation of nature, and increase awareness of our dependence on biodiversity and the need to conserve it and use it wisely," Elmqvist concludes.
See video with Thomas Elmqvist explaining the many links between urbanization, biodiversity and ecosystem services: