Beyond “bluespace” and “greenspace”: A narrative review of possible health benefits from exposure to other natural landscapes

Highlights

• Greenspace and bluespace research is booming, but nature is not always green or blue.

• Color-coding natural landscapes could provide confusing and misleading descriptions.

• Natural landscapes are largely composed of plants, water, and rocks/minerals.

• Caves, deserts, and landscapes with ice/snow may pose health benefits and risks.

• More high-quality research on the broad array of natural landscapes is needed.

Abstract

Numerous studies have highlighted the physical and mental health benefits of contact with nature, typically in landscapes characterized by plants (i.e., “greenspace”) and water (i.e., “bluespace”). However, natural landscapes are not always green or blue, and the effects of other landscapes are worth attention. This narrative review attempts to overcome this limitation of past research.

Rather than focusing on colors, we propose that natural landscapes are composed of at least one of three components: (1) plants (e.g., trees, flowering plants, grasses, sedges, mosses, ferns, and algae), (2) water (e.g., rivers, canals, lakes, and oceans), and/or (3) rocks and minerals, including soil. Landscapes not dominated by plants or liquid-state water include those with abundant solid-state water (e.g., polar spaces) and rocks or minerals (e.g., deserts and caves). Possible health benefits of solid-state water or rock/mineral dominated landscapes include both shorter-term (e.g., viewing images) and longer-term (e.g., living in these landscapes) exposure durations. Reported benefits span improved emotional and mental states and medical treatment resources for respiratory conditions and allergies. Mechanisms underlying the health benefits of exposure consist of commonly discussed theories in the “greenspace” and “bluespace” literature (i.e., instoration and restoration) as well as less discussed pathways in that literature (i.e., post-traumatic growth, self-determination, supportive environment theory, and place attachment).

This is the first review to draw attention to the potential salutogenic value of natural landscapes beyond “greenspace” and “bluespace.” It is also among the first to highlight the limitations and confusion that result from classifying natural landscapes using color. Since the extant literature on natural landscapes - beyond those with abundant plants or liquid-state water - is limited in regard to quantity and quality, additional research is needed to understand their restorative potential and therapeutic possibilities.

Introduction

The health benefits of contact with nature are widely recognized across human cultures. For example, 天人合一 (the harmony between humanity and nature) is a core idea in Chinese culture (Lai et al., 2022). Shinrin-yoku, or forest bathing, is an increasingly popular form of nature therapy used to promote physiological and psychological health in many parts of the world (Hansen et al., 2017). American poet Ralph Waldo Emerson described “the lover of nature is he whose inward and outward senses are still truly adjusted to each other; who has retained the spirit of infancy even into the era of manhood” (Emerson, 1903, p. 9), inspiring a fascination with nature-based health promotion in Western countries (Larson and Hipp, 2022). Modern empirical research supports a strong link between nature and human health, but it also highlights potentially variable effects across diverse types of natural landscapes via different mechanisms (Hartig et al., 2014).

The health-promoting potential of nature exposure is often assumed to be driven by our genes (Kaplan and Kaplan, 1989; Wilson, 1986; Ulrich, 1983), an adaptive trait paralleled with biophilia, meaning humans’ inherent affinity for other forms of life (Kellert and Wilson, 1993). Most of human evolutionary history has occurred in natural surroundings (Joye and van den Berg, 2011; Moura et al., 2017). Not until recent centuries, following the industrial revolution, have a majority of humans lived outside of and apart from nature-rich environments (Turner et al., 2004; Vlahov and Galea, 2002). Therefore, while humans' direct connection with natural environments may be diminishing, our evolutionary-driven connections with natural landscapes and resulting health impacts are likely to remain viable today (Laland and Brown, 2006; Robinson and Breed, 2020).

Scholars have proposed the “therapeutic landscape” concept to explain why certain places contribute to health promotion and treatment. With roots in cultural ecology, structuralism, and humanism (Gesler, 1992; Williams, 1998), this concept spans multiple dimensions of wellbeing including material/physical, social, and spiritual (Bell et al., 2018). The physical environment of therapeutic landscapes includes natural and human-made environments (Gesler, 2018). Natural landscapes characterized by plants and liquid water have received perhaps the most attention (Bell et al., 2018; Bell et al., 2017). This focus is not surprising, as these two elements are common components in many natural landscapes inhabited by people. They also supply basic resources for survival (Reid et al., 2005). Water is a fundamental part of life, and plants provide many ecological services, including the production of organic matter for food and oxygen for breathing (Carpenter et al., 2009). For these reasons, much research has been conducted on the health benefits of natural settings rich in these ecosystem services (Bratman et al., 2019; Zhang et al., 2020).

Studies on the health benefits of plant and liquid water-dominated landscapes often use color schemes to code landscapes with these components (Twohig-Bennett and Jones, 2018; White et al., 2020). In this context, “greenspace” refers to landscapes rich with plants (e.g., trees, flowering plants, grasses, sedges mosses, ferns, and algae), and “bluespace” refers to landscapes with open water (e.g., canals, rivers, lakes, oceans). However, nature is not limited to plants or open water, and this binary characterization omits key components of potentially therapeutic natural landscapes.

Emerging concepts such as “white space” (e.g., snow-covered landscapes; Brooke and Williams, 2021; Finlay, 2018; Korpela et al., 2014; Olwig, 2005; Yli-Panula et al., 2022), “brown space” (e.g., deserts; Nazif-Munoz et al., 2020; Olvera-Alvarez et al., 2021; Yin et al., 2022), and “red nature” (e.g., volcanoes; Kotera et al., 2021) bring more types of landscapes into scholarly discourse. Human perceptions of landscapes are undoubtedly shaped by sight and visual attributes, such as color, that contribute to experiences related to place (Bell, 2012; Lengen, 2015; Zhang et al., 2022). Nevertheless, there are limitations to the use of color-coding to describe natural landscapes. Non-visual sensory perceptions such as sound may have a strong influence on the health benefits associated with nature (Buxton et al., 2021). Additionally, color may not clearly indicate landscapes that are alien to most people. For example, general readers may not associate “red nature” with volcanoes without extra description (Kotera et al., 2021). To add more complexity, plants and water change color with time, season, and place, which might limit the relevance of the classic “green” and “blue” coding (Zhou et al., 2022).

Some studies have revealed the psychological benefits of landscapes that have few plants or minimal liquid water, such as deserts (Yin et al., 2022). Scholarly examination of the shorter-term psychological and physiological responses to these landscapes, and the health outcomes associated with longer-term exposure of living in these settings, may challenge the consensus that people prefer natural resource-rich environments (i.e., those with abundant plants and/or liquid water). These clues underscore the importance of expanding the definition of nature beyond “greenspace” and “bluespace.” These clues also emphasize the need to explore potential mechanisms driving the health benefits associated with exposure to natural landscapes that have been discussed in the nature-health literature less commonly.

The first objective of this narrative review is to develop a framework that categorizes the broad array of natural landscapes that is not based solely on color. The second objective is to review the available literature on the possible health benefits of exposure to natural landscapes that are not dominated by plants or liquid water. The third and final objective is to identify possible mechanisms that might explain how shorter-term and longer-term exposure to these landscapes can promote human health and well-being.