Biodiversity is important to cities beyond its contribution to overall conservation efforts. Green spaces in cities serve as critical migratory corridors for some species. People want access to nature and the services that come with it (Maddox, 2012). A 10% increase in urban tree canopy cover can result in 3-4 degree Celsius decrease in ambient temperature, reducing the need for air conditioning. However, one of the most compelling arguments for urban biodiversity is the health benefits. Rich diversity in cities contribute to ecosystem services such as improved air quality, dust filtering, and acting as a carbon sink. Proximity to plant life can reduce prevalence of childhood asthma and allergies (Simonsen, 2012). These are just a few examples of the myriad health benefits that biodiversity provides, but the bulk of investment in biodiversity conservation efforts currently focuses on land that is far away from population centers. However, given the health implications as more people move into in cities, a greater effort should be put toward studying and protecting urban biodiversity. Change can come through developing better protection schemes and incorporating considerations for biodiversity into urban design (Maddox, 2012), as well as community based efforts.
One mechanism for increasing urban biodiversity is to support urban agriculture efforts. Some cities already utilize urban farming a great deal; a 1996 UN report estimated that up to 80% of families in some Asian cities and others around the world are involved in agriculture. Urban agriculture itself has huge public health implications. Gardens can strengthen local food security when paired with support in the form of knowledge, tools and space. Though many variables affect agricultural outputs, given average growing conditions, a 10 by 10 meter plot can provide a household’s yearly vegetable needs including much of the nutritional requirements for vitamins A, C, B complex and iron (Brown and Jameton, 2000). While such a plot may not be a viable option for many city dwellers, smaller plots or community gardens can still contribute to increased nutrition. Gardens also contribute to improved personal wellness. Research supports the associated benefits of physical exercise, stress release, and other psychological and social benefits (Brown and Jameton, 2000). In fact, naturally occurring soil bacteria can act directly as a mood enhancer. One bacterium, mycobacterium vaccae, boosts serotonin levels and reduces anxiety (Healthy Organic).
There’s a caveat, however, for plant based biodiversity programs. A study of changing biodiversity patterns in cities found that plant species richness increases because of importation, but animal species richness tends to decline. This is because humans directly control plants but almost never animals and microbes—the implication being that conserving natural habitats defined by plants doesn’t guarantee the other components of biological community (Faeth et al., 2011). The fauna and microbes in a community are crucial for biodiversity and the ecosystem services they provide. This should be accounted for more in urban biodiversity efforts.