What We Still Don’t Know about the Health Benefits of Nature

ASLA 2017 Professional General Design Award of Excellence. Klyde Warren Park, Dallas, OJB Landscape Architecture / Gary Zonkovic Photography

We know that connecting with nature is good for us, but there are still many questions that need to be answered through more credible scientific research: What is the ideal “dose” of nature? What health conditions do these doses actually help with? Does duration and frequency of dose matter? How long do the benefits last? Does who you are and where you live impact how beneficial exposure to nature will be? And how does technology help or interfere with our connection to nature?

To get a better handle on the remaining unknowns, leading public health expert Dr. Howard Frumkin assembled a multi-disciplinary team at the University of Washington comprised of experts in epidemiology, environmental health, clinical medicine, psychology, ecology, landscape architecture, urban studies, and other disciplines, along with experts from the Nature Conservancy, Seattle Children’s Research Institute, U.S. Forest Service, Willamette Partnership, Stanford University’s Center for Conservation Biology, and the Natural Capital Project. Together, they crafted a creative, ambitious research agenda, which was just published in Environmental Health Perspectives.

According to Frumkin and the other co-authors, “nature contact offers considerable promise in addressing a range of health challenges, including many — such as obesity, cardiovascular disease, depression, and anxiety — that are public health priorities. Nature contact offers promise both as prevention and as treatment” at all stages of life.

Furthermore, exposure to nature is likely cheaper than “conventional medical interventions,” safe, practical, and doesn’t require a highly-trained professional to dispense treatments. Green spaces designed to provide health benefits of nature also offer many co-benefits: they provide wildlife habitat, store stormwater, or offer shade, for example.

While the benefits of nature are increasingly understood, the team found seven domains where further research is needed. Below are high-level summaries; for greater detail, read the research agenda.

Mechanistic Biomedical Studies: We need to better understand how nature exactly works its magic on us. While some scientists believe the mechanisms, or pathways of impact, on our minds and bodies have an evolutionary origin, meaning they are deep-rooted and associated with our innate biophilia, others posit there may be more precise pathways that are psychological, relate to our immune system, or are linked with increased social contact or improved air quality. We don’t know exactly the way nature exposure works its benefits on us.

Just in terms of psychological pathways, there are a diversity of theories: some argue that nature helps by relieving stress, while others focus on the way nature can relieve mental fatigue. Those are different things. And there could be multiple mechanisms happening at once, too. Frumkin and team argue that with more research “specific neural pathways” for these benefits will likely be discovered.

There is also some research suggesting exposure to nature boosts immune function; physical activity outdoors in a green space is better than in a gym; being in nature promotes the creation of social connections, which in turn provide health benefits; and trees and other green spaces, particularly in cities, reduce air pollution, creating health benefits.

But the research agenda notes that much more evidence-based research is needed to isolate the exact mechanisms through which nature exposure works its theorized benefits.

Exposure Science: Epidemiologists try to measure the “magnitude, frequency, and duration of exposure to an agent, along with the number and characteristics of the population exposed.” When “researching the environmental impacts on people,” research focuses on “pathogens, medications, toxic chemicals, and social circumstances, or salutary exposures such as nature.”

However, they argue that “standard approaches to exposure measurement” have limitations. “First they fail to capture variations in how people in how people experience nature, nuances that may be highly relevant. Suppose that one person sits in a car atop a seaside bluff and admires the view of the beach (while checking email on a smartphone), a second person walks barefoot along the shore, enjoying not only the view, but the feel of the sea breeze and the lapping waves, and a third person plunges in a for a swim. The designation ‘beach contact’ or a measure of ‘time on a beach’ would fall short of capturing the variation in their experience.”

As such, measuring the effects of various doses of nature becomes more complicated — someone paying close attention to all the details while on a forest path and really immersing themselves in the experience and another person simply walking through while looking at their smartphone will “likely ‘absorb’ differing levels of nature.”

Epidemiology of Health Benefits: Epidemiologists, who research the health and disease profiles of populations, conduct “true experiments, ‘natural experiments,’ and observational studies.” The bulk of research on nature contact and health have been observational studies, which Frumkin and his team argue are practical, can be conducted rapidly, and reduce costs of research, given they typically use data collected for other purposes. However, there are also built-in limits to the pre-existing data, and it’s hard to control bias in these studies.

True experiments, which are clinical trials, are the “gold standard” in science. Natural experiments, which “are study opportunities that arise through circumstances outside the investigator’s control” — like Roger Ulrich’s famous study of hospital patients, their views of trees, and recovery times — enable researchers to test hypotheses in realistic settings. More of these studies are needed.

The group also recommends nature and health researchers do a better job of tapping into existing large-scale research studies and data sets; finding new sources of big data, such as using Google Street View, webcams, and location-based data-collection apps like Mappiness; and investing in more advanced statistical analysis and advancing epidemiological research in general.

Diversity and Equity — The Role of Nature Contact: More research is needed to better understand “a) patterns of disproportionate exposure; b) cultural and contextual factors that affect nature preferences; c) differing patterns of benefit across different populations; and d) the possibility that improved access to nature may have unintended negative consequences on vulnerable populations.”

As has been explored by other researchers, low-income communities are more likely than not to also have limited access to nature and green space, which only exacerbates the negative health impacts of poverty, bad diets, lack of exercise, and crime.

African Americans, Frumkin and his team write, may also have different associations with trees, fields, and forests than other groups, due to the legacy of “forced labor, lynchings, and other violence.” 

And livelihoods play a role in creating different understandings of what’s restorative: “a rural farmer has quite different preferences regarding nature from those of an urban computer programmer.”

On the positive side: there is some research that argues that access to nature and green space may disproportionately help those in low-income communities who suffer from unequal access to many services, but, again, more study is needed.

Technological Nature: Modern technologies — the Web, smartphones, games, virtual reality (VR), the list goes on — are altering our relationship with nature. Kids, who spend more and more time glued to their screens, are particularly impacted. But there are also other kinds of technologies  — those that “mediate, simulate, promote, and/or augment the human experience of nature,” which must also be better understood. Computer desktop wallpaper of nature scenes, VR movies in which users go on safari in Africa, and location-based games like Pokemon Go may offer some of the benefits of nature exposure — and may be better than nothing — but more laboratory-based experiments are needed.

Economic and Policy Studies, including Co-benefits: The benefits of nature are increasingly being quantified. As such, policies are being promoted to increase the value of these benefits for communities and ecosystems. Frumkin and the co-authors propose looking to ecological and health economics for new models of evaluation and quantification of the benefits of nature as well as the avoided health care costs.

When the value of a new park is estimated, it’s important that policymakers don’t just look at improvements in real estate value or gains in stormwater credits, but also the real, quantifiable community health benefits. Furthermore, cost-benefit analyses rooted in benefits valuations can help guide limited public funds towards the most effective forms of green space investment.

We couldn’t agree more. It’s critical to answer: What policies and regulations can positively boost the health benefits of nature and which don’t do much at all? Many cities aim to provide a park within a five minute walking distance of every resident. Is this a worthy policy? Toronto just created a shade policy to help reduce the negative health impacts of heat in the summer. What metrics should be used to measure the success of such policies?

Implementation Science — Studies of What Works: “Research findings don’t necessarily translate into action.” This group wants to see more what “intervention studies are needed to determine what works in practice.”

As an example, they point to the U.S. Forest Service’s iTree software, which helps anyone with a computer understand the ecosystem service benefits of the trees they are planting. The researchers ask: “might further development of such tools incorporate additional mental and physical health benefits?”

While this research agenda is impressive and comprehensive, there are a few other unknowns important to include:

First, doctors are now prescribing time in the park. Do these treatments, which often combine increased activity, social interaction, and nature exposure work? Is the combination of exposure, social engagement, and exercise what is key?

Second, what is the impact of climate change on the nature and health connection? As nature becomes a more changeable, and often destructive force, in many places, do we need to differentiate between safe and unsafe nature spaces? Can an ocean that floods a community every year be considered restorative when it isn’t causing damage?

Lastly, there are landscape architecture educators and researchers, like William Sullivan, ASLA, and MaryCarol Hunter, ASLA, who seek to determine which forms and arrangements of landscape elements have the most benefits. Their forward-looking studies are critical: The next step is to translate proven health benefits from nature exposure into design principles planners, landscape architects and designers, and engineers can apply in their work. What designed landscape forms and elements act as pathways to the biggest benefits?

New Guide: Energy Efficiency at Home

By using passive solar heating and an extended roof of photovoltaic panels, these houses produce more energy than they consume. The Solar Settlement in Schlierberg, Freiburg, Germany / Wikipedia

Inefficient home energy use is not only costly, but also contributes to the growth of greenhouse gas (GHG) emissions, the primary cause of climate change. According to the U.S. Energy Information Administration, the residential sector accounted for 21 percent of total primary energy consumption and about 20 percent of carbon emissions in the U.S. in 2013. And according to Architecture 2030, building construction and operations-related energy use accounts for almost 50 percent of total GHG emissions.

Through integrated site design, a comprehensive approach to sustainable building and site design, sustainable residential landscape architecture practices can not only improve the environment, but also result in net-zero or even climate positive homes. If part of a broader integrated site design, sustainable residential landscape architecture can help eliminate the need for fossil fuel-based energy, while creating a healthy residential environment.

ASLA has created a new guide to increasing energy efficiency through sustainable residential landscape architecture, which contains research, projects, and resources. Developed for homeowners and landscape architects and designers alike, the guide is designed to help spread more sustainable and resilient practices.

Homeowners can go net-zero or climate positive by tapping the potential of landscapes. As an example, residential green roof and wall systems, which are often key features of integrated site design projects, can reduce energy use and home heating and cooling costs.

According to The Sustainable SITES Initiative™ (SITES®), homeowners can use trees and dense shrubs to shade their home and any external HVAC systems or block wind and thereby further reduce energy use.

Homeowners can further leverage clean energy technologies, like solar-powered LED outdoor lighting.

The environmental and economic benefits of energy efficient technologies increase as homes are tied together into multi-family housing complexes with shared infrastructure. Research shows dense development lowers water and energy use, conserves natural habitats, and reduces transportation-related GHG emissions by encouraging walking, cycling, and taking public transportation. Communities like Freiburg, Germany and Malmo, Sweden are examples of residential communities that have taken innovative approaches to design and planning by implementing sustainable energy, water, and waste management systems.

Landscape architects can help homeowners by undertaking a comprehensive energy audit and then identify landscape-based solutions for generating renewable power or reducing energy waste.

State and local governments also work with design professionals to incorporate sustainable residential landscape architecture codes throughout urban, suburban, and rural areas. For example, South Miami just recently mandated that new buildings, and some renovations, must include solar panels.

Source: Drivers of U.S. Household Energy Consumption, 1980-2009, U.S. Energy Information Administration

Explore the guide:

Green Roofs
Green Walls
Tree Placement for Energy Efficiency
Solar