Post written by Julia Africa, Program Leader, Nature, Health, and the Built Environment at the Center for Health and the Global Environment

The great beating heart of the biophilic cities proposition, a colleague recently pointed out, is its fearless use of the word “love”; urban greening frameworks rarely cast our innate affinity for nature in such fundamentally emotional terms. By contrast, the exsanguinated language of applied economics does a particular disservice to the spiritual and sensorial benefits of biodiverse urban environments by reducing them to functional attributes (e.g., “the value of biodiversity change to society depends on the net marginal effect of the change on all ecosystem services”). Increasingly, the  term ‘ecosystem services’ has widened to accommodate the particular characteristics of urban green that support psychological and physiological health and well-being.  This, in turn, has generated interest in the public health community, and spurs planning synergies that change the practice of preventative care and chronic non-communicable disease management by harnessing biophilic environments.[i]

In part through efforts like the Biophilic Cities Network, urban planners and designers continue to iterate on strategies for bringing exposure to nature into city life at every scale. The ordered complexity found in natural environments is key to their intelligibility and, indeed, enduring allure. The eddies and swirls of seasonal winds, the fractal branching of trees, the low murmur of streams and Fibonacci structure of flower petals  all provide unconscious and conscious cues  that settle the addled mind.[ii] Hybrid urban ecologies serve many purposes ranging from notional nostalgic refuges and functional exercise havens to contaminant reduction and climate-change mitigation infrastructure. Although implicitly linked to human health and well-being, their explicit role in supporting human health has begun to receive sustained attention. For instance, recent studies suggest that factors like  views of nature from classroom windows or residential proximity to green space  improve student performance on standardized tests regardless of region or grade level. Less work has been done on the contribution of natural sounds.

However, at a core level – and at a lamentably young age – common urban contaminants tragically  narrow the potential of countless children worldwide. Common hazards include exposure  to methylmercury and lead which are independently correlated with lowered IQ, aggression, speech delays and even (in the case of lead) increased rates of incarceration.[iii] A recent article documented  similar developmental effects in songbirds. Science tells us that songbirds sing for many reasons such as courtship, turf, and warning, among others. The extraordinary breadth of sounds found in a ‘dawn chorus’ bring bleary-eyed mornings into focus; each species has its own rhythm, tempo and pattern, some so flamboyant that one might be convinced that they sing for the sheer joy of it. Just as with human speech, heavy metal exposure changes their songs. Songbirds contaminated with methylmercury have been shown to sing shorter, simpler, lower pitched songs, and birds near a smelter in northern Europe with “a lot of heavy metal contamination knew fewer songs and sang less at sunrise than birds at two less polluted sites.” The story doesn’t end with metals, of course; chickadees exposed to Hudson River polychlorinated biphenyls “sing strange songs.”[iv] Whistle, trill, chirp and caw: the increasingly garbled sounds of our disordered environment are often invisible but perceptible if we listen.

Do changes in these songs matter affect observed rates of human ‘restoration’? I think so. Nature sounds, when compared to urban noise, allow for physiological and psychological restoration to occur up to 37% faster after exposure to a psychological stressor.[v] Participants in a UK study comparing tranquility ratings of scenes with and without coupled audio tracks noted that participants tolerated higher noise levels when they were associated with biodiversity.[vi] Studies suggest that we prefer moderate sound levels (65-70 decibels) of ambient noise with the kind of layered, fractal complexity found in streams flowing over rocks or wind in the trees. The psychological benefits of nature increase with higher levels of biodiversity; these benefits increase with biodiversity and not with an increase in natural vegetative area[vii], reminding us that complexity and integration rather than quantity is critical. One might imagine that Twitchers – as bird-watchers are known – are the canaries in the biophilic coalmine when it comes to spotting disordered songs, but one wonders if the discrepancies are great enough to excite the interest or dis-ease of the average person. Is a natural sound still sound restorative if it emerges warped? To my knowledge, no one knows the answer to this particular question. But the worldwide decline of songbird species suggest that we stand to lose (among other things) both individual strands of songs as well as the auditory tapestry  of a chorus in the morning and, by extension, some of our most cherished daily moments of communion and reflection.

I recently attended the IUCN World Parks Congress in Sydney, Australia and was intrigued by a new term: ‘climate refugia’. The sober doctoral student who shared her  research with me explained that she studied territories that – by virtue of topography, species composition, or other characteristics – are considered less susceptible to ecological perturbance. It seems that perturbance is to ecologists what allostastic load[viii] is to public health clinicians. Both terms capture individual and communal responses to environmental stressors and the degree of adaption or accommodation that is possible in a given system at a given time. Disease and death can follow from a system that is stressed beyond its adaptive capacity. Can cities be our allies in restoring and sustaining adaptive capacities? That question lies at heart of all future urbanisms and is a critical contribution made by the Biophilic Cities model. I am hopeful that birdsong and humansong alike will find ways to flourish in our increasingly urban future.


[i] Cardinale, B. J., Duffy, J. E., Gonzalez, A., et al. 2012. Biodiversity Loss and its Impact on Humanity. Nature 486: 59-67

[ii] Africa, J.,  Logan, A., Mitchell, R., Korpela, , K., Allen, D, Tyrväinen, L., Nisbet, , E., Li, , Q, Tsunetsugu, Y.,  Miyazaki, Y., Spengler, J.; on behalf of the NEI Working Group. 2014. The Natural Environments Initiative: Illustrative Review and Workshop Statement. Center for Health and the Global Environment at the Harvard School of Public Health. accessed 11.23.24

[iii] Ryan, C.O., Browning, W.D., Clancy, J.O., Andrews, S.L., Kallianpurkar, N.B. 2014. Biophilic Design Patterns: Emerging Nature-Based Parameters for Health and Well-Being in the Built Environment. Archnet-IJAR 8(2): 62-76 Regular Section

[iv] Carpenter, D.O. & Nevin, R. 2010. Environmental Causes of Violence. Physiology & Behavior 99(2): 260–268  Accessed 11.23.14

[v] Alvarsson, J. J., Wiens, S., & Nilsson, M. E. 2010. Stress Recovery during Exposure to Nature Sound and Environmental Noise. International Journal of Environmental Research and Public Health, 7: 1036-1046.

[vi] Pheasant, R., Horoshenkov, K., Watts, G. 2008. The acoustic and visual factors influencing the construction of tranquil space in urban and rural environments tranquil spaces-quiet places? J. Acoust. Soc. Am. 123(3): 1446-1457

[vii] Fuller, R. A., Irvine, K. N., Devine-Wright, P., Warren, P. H., & Gaston, K. J. 2007. Psychological benefits of greenspace increase with biodiversity. Biology Letters, 3: 390-394.

[viii] Juster, R.P., McEwen, B.S., Lupien, S.J. 2009. Allostatic load biomarkers of chronic stress and impact on health and cognition. Neuroscience and Biobehavioral Reviews 35(1):2-16

Photo by Rose Lincoln, Harvard Public Affairs and Communications Office

Julia Kane Africa leads the ecological infrastructure, biophilic design and restorative landscape areas of the Nature, Health, and the Built Environment (NHBE) program. In this role, she examines the ways in which nature (parks and green spaces) and natural design cues (natural features in built environment settings) in urban settings support psychological and physiological health and resilience. She then translates these insights into urban design and planning practices that are site-sensitive, ecologically ethical, and health-promoting.

Ms. Africa has completed graduate coursework in environmental health, exposure assessment and sustainable design at the Harvard School of Public Health and the Harvard Graduate School of Design (MDesS). She also holds previous degrees in Acupuncture and Oriental Medicine (MAOM) and Cultural Anthropology (BA).

A recent paper Africa co-authored on the links between health and green space can be found at .

Author Note: I am indebted to Karen Trevino, Chief of the US National Park Service’s Natural Sounds Night Skies Division, for bringing the qualities and capacities of natural sounds to my attention so many years ago.