You've heard it before; exposure to nature is good for you. Most research on environment and human health focuses on landscapes dominated by vegetation and bodies of liquid water. However, these so-called "green" and "blue" spaces only describe a fraction of Earth's ecosystems. What about other landscapes, such as caves, deserts or glaciers?
A new paper is the first review that draws attention to the potential value of environments beyond greenspace and bluespace. The authors created a rubric to classify an environment based on its natural elements, rather than confusing color-coded language. They created three distinct categories-landscapes dominated by plants, rocks and minerals or water, including frozen landscapes. They identified existing studies that focused on non-greenspaces/bluespaces, and solid-state water, such as polar regions. In addition to what the benefits were, the authors identified what mechanisms, or pathways, that underlay those benefits.
"We looked at studies focused on wild places-expeditions to the Arctic, cave therapy in China and others focused on high mountain landscapes," said Alessandro Rigolon, assistant professor of city and metropolitan planning, and co-author of the review. "There was a breadth of different kinds of landscapes that show some beneficial factors. That was surprising to me-some of these places are not what you would consider this hospitable, right? Where humans have settled in small numbers. Why is that?"
The review, published Jan. 15, 2023, in the journal Science of the Total Environment, found that health outcomes from solid-state water or rock/mineral dominated landscapes resulted from both shorter-term (viewing images) and longer-term (living in the landscape) exposure. The reported benefits fit across a spectrum, from improved emotional and mental states to medical treatments for allergies. The mechanisms underlying the health benefits consisted of common theories from bluespace/greenspace literature, such as restoration, and less discussed pathways, such as self-determination and place attachment. There were also risks associated with exposure to these environments, including mobility issues, seasonal affected disorder and allergies. The authors say that much more research is needed to understand the restorative potential and therapeutic possibilities beyond greenspaces and bluespaces.
Landscapes dominated by solid-state water
The authors found little evidence of benefits from short-term exposure to landscapes dominated by solid-state water. However, cruises to the North Pole and guided glacier hikes indicate a fascination with ice-dominated landscapes, suggesting an emotional benefit that has yet to be uncovered. Alpine regions in the European Alps, Himalayas, Andes and the Wasatch Mountains' "Greatest Snow on Earth" attract crowds of visitors every year, suggesting that outdoor recreation activities promote fitness and generate emotional and social benefits.
The authors also found clues to the health benefits of longer exposure to icy/snowy landscapes from studies of polar expeditions or military deployment. One review of Antarctic psychological research found that the lack of modern conveniences and responsibilities improved people's moods and emotions. Other studies found that living in polar spaces for long periods spurred personal growth and improved well-being. The authors note that the study subjects were expedition members or soldiers that were trained to have a higher adaptability to extreme environments, so findings from this research might not apply to broader populations.
Landscapes dominated by rocks and minerals
Landscapes dominated by rocks and minerals include caves and both cold and dry-heat deserts. Caves are subterranean environments that often lack plants due to low sunlight. The authors found no evidence of benefits from short-term exposure to caves, but they point out that caves with stalactites and stalagmites attract more than 70 million visitors globally every year. Given their appeal, caves may promote positive emotional responses. The authors also found evidence that cave climates may be therapeutic for physical ailments. For example, speleotherapy involves breathing the unique air in caves, and halotherapy involves breathing air with airborne dry salt in an enclosed space that mimics salt caves. These therapies require longer-term exposure, and numerous studies have outlined their potential to treat afflictions from asthma and skin allergies to chronic obstructive pulmonary disease.
Based on the authors' review, only dry-heat deserts have been researched for potential health benefits. A study of college students from Saudi Arabia exposed to one minute of a familiar coastal desert video performed better on a memory test than students exposed to an unfamiliar temperate forest video.
"This finding suggests that people's familiarity with the predominant natural landscape where they grew up might play a role in the benefits that such landscape brings to them," said Rigolon. Other studies that exposed participants to images or short walks in the desert found that they have a calming effect.
Longer-term exposure also impacted people. One experimental study found that during a four-day trip to the Utah desert, participants' brain activity suggested their environment held their attention. Studies in Kenya and along the Israel/Jordan border revealed that living in the desert supported physical and mental well-being by offering freedom of movement and a sense of peace. Some medicinal therapies originated in desert landscapes, such as Uyghur sand therapy that uses sand heated by the sun to cure chronic osteoarthritis.
What drives health benefits?
To develop their new framework, the authors adapted three factors in greenspace/bluespace literature that link nature exposure to health. The first, harm reduction, refers to components of the landscape that mitigate noise, heat or air pollution. The researchers found no evidence of harm reduction from the rock/mineral and solid-state-water landscapes but included it for future research outcomes. The second, restoring capacity, refers to recovery from negative states, such as stress or fatigue. The third, building capacity, refers to natural landscapes' ability to promote health through experiences, such as promoting social cohesion or physical activity.
The authors found evidence that these landscapes do promote restoring and building capacities. Many studies revealed that they restored attention spans, reduced stress and some covered therapies that addressed post-traumatic stress disorders.
What's next?
Though the narrative review revealed some exciting health benefits from non-greenspaces/bluespaces, much more research is needed to address the gaps in the literature. Rigolon and colleagues have also published a paper that present a new dataset mapping all accessible and recreational public lands in the U.S., from local fields to national parks, including natural environments dominated by rocks and minerals. This dataset will allow them to study associations between rock/minerals dominated landscape and health outcomes on a broader scale than done so far. Locally, they're also exploring whether guided walks through a garden and arboretum have positive impacts on older adults with dementia.
Rigolon concluded, "Living in Utah, it was exciting to find that desert and snowcapped landscapes have similar health benefits to landscapes dominated by vegetation. They show that tourism in our snowcapped mountains and red rock country can have great benefits for people's mental health. One more reason to spend time outdoors."
