Lesson 4: Health and our Environments

The word ‘nature’ has several meanings. It can refer to the essence, inner quality, and character of an object or phenomenon, the whole of material reality that is independent of Human activity and history, or the entirety of the Universe (source).

We define Nature as theentirety of living and biological beings in our habitats and on our Planet; where the beings are those who have Life and those who support Life: Trees, Water, Air, People and non-Human Animals, Bacteria, Insects, Fungi, and Soil.

In an urban context, we must recognise that Nature’s care, conservation, propagation, diversity, and distribution is often at the whim of People. Therefore, it is imperative that cities and those that work in city infrastructure take into consideration how their work impacts Nature; more specifically, we need to acknowledge how we allow Nature to lead and grow at their own pace.

It is important to note that one of the pathways to having a better relationship with Nature is in how we refer to them. 

First, Nature is not an ‘it’ because an ‘it’ does not have Life (source), even if historically an “it” has been used to describe an entity that does have life. 

Second, we will not refer to Nature by any other descriptor that denotes a non-living quality. 

Third, everyone in Nature has a being and, thus, is equal to People; therefore, we will use them/they and other Human-based pronouns to refer to Nature. 

Finally, all Nature will be capitalised to stress their significance.

Switching the linguistic framing is an important step in forming a more respectful and kindred relationship with Nature. Framing Nature as an ‘it’ is not only inaccurate because Nature has Life, but it also denotes that Nature is a ‘thing’. Given the capitalist proclivities of our society, ‘a thing’ is often meant to be owned, consumed, or possessed. 

For millennia, Indigenous Peoples all over the world have cognitively framed Nature as Kin, which means that Nature is our direct relation, the same as a Human friend or relative. Furthermore, in recent history, environmental scientists, activists, and lawyers are giving Nature a Personhood to give them full Human Rights (source). This is to protect Nature from oppression, contamination, and destruction. 

Many of us visit Nature to take a break, to relax, and to rest. When we are tired, stressed, or in a bad mood, visiting Nature helps us to restore cognitive and affective resources and to recover from stress. To benefit from these positive effects on our mental health and well-being, we may go on a long holiday to the Mountains or the Sea. However, we also visit Nature in everyday Life, for example, to prepare mentally for a meeting, to recover from a stressful work day, or to cope with negative Life events.

There are two theories that address the positive impact of Nature on mental health: the attention restoration theory (ART) and the stress recovery theory (SRT). Both were developed in the 1980s and 1990s, and, since then, much evidence has accumulated that supports the idea that exposure to Nature does indeed restore/recover our cognitive and affective capacities (source, source).

Essentially, the two theories describe our fascination with elements of Nature that are linked to effortless attention (allowing us to restore exhausted cognitive resources) and our innate connection to Nature (allowing us to recover from stress from our daily lives). Visiting Nature can help us to cope with mental exhaustion and with psychosocial stressors that, otherwise, impact negatively on our physical, mental, and social health and well-being.

Using the current scientific knowledge, it is possible to identify several mechanisms that underlie the link between Nature and health. Mechanisms describe the causal relationship between a stimulus/exposure (i.e., a component of Nature) and the health-related response/outcome (e.g., the regulation of the immune system). In other words, mechanisms describe how the exposure (Nature) affects the outcome (health). The mechanisms underlying the link between Nature and healing are categorised into six broad pathways. For each pathway, there would be several examples of mechanisms underlying the Nature-healing relationship.

The following pathways are written in a linear format to create clarity, however they often work in tandem and even simultaneously. For example, a person going for a run will be exposed to exercise, social interaction, immune regulation, spirituality, and, consequently, will experience the healing outputs in a systemic and simultaneous manner as well.

1. Biological (e.g., the pathway to immune regulation)

2. Psychological (e.g., the pathway to reducing stress and anxiety)

3. Social (e.g., the pathway to promoting community cohesion)

4. Physical activity (e.g., the pathway to facilitating exercise and associated cardiovascular benefits)

5. Spiritual (e.g., the pathway to enhancing spiritual well-being)

6. Environmental buffering (e.g., the pathway to reducing pollution and the associated respiratory benefits)

It’s important to note that allowing people to achieve these goals means addressing some of the historical injustices that have seen people removed from a connection with Nature; Displacement, time constraints driven by economic inequities, racism, ableism, and classism all contribute to a disconnection. Addressing these factors is crucial to enabling healing through Nature in urban environments.

For more on this please read Nature, Cities, Health and Healing.

The microbiome can be defined as the entire collection of microbes (bacteria, algae, archaea, fungi, protozoa, and viruses) in a given environment, and its ecological theatre of activity. In the scientific realm, we tend to separate the microbiome into the environmental microbiome and the human (or animal) microbiome; but, really, both interact with each other in a constant flux of activity.

What is the environmental microbiome?

The environmental microbiome refers to the microbial communities that reside in the soil, the water, the plants, and the air (also known as the ‘aerobiome’). In terms of diversity, the soil is one of the densest habitats on Earth. A single teaspoon of soil would likely contain between 10,000 and 50,000 different microbial species. There are approximately one trillion different microbial species in our planet’s natural environments. This is ten times as many species as there are stars in the Milky Way. Each environment has its own unique microbiome. The environmental microbes play vital roles in the functioning of our ecosystems.

What is the human microbiome?

The human microbiome is the collection of microbial species that live in and on our bodies. Each body site has its own unique microbial community. For example, the microbiome of our armpits is distinct from the microbiome of our mouths or guts. The gut microbiome is the densest microbial habitat in the human body, with trillions of bacteria, viruses, fungi, and others calling it their home. The genes in our microbiome outnumber our own ‘human’ genes by 150 to 1, and if we could extract the microbes from a single person’s gut and line them up, they could circle the Earth 2.5 times. The microbes in our bodies play essential roles in maintaining our health and ‘homeostasis’ by regulating our immune system, digesting our foods, and providing chemicals to keep our cells and organs in a healthy state.

How do the environmental and the human microbiome interact?

The microbes that live in our bodies are supplemented by the microbes in the environment and the microbes in our foods. There are approximately a million microbial cells in a single cubic metre of air, and people can inhale a whopping 100 million bacteria each day. In essence, the microbes in and on our bodies and the microbes in the environment are constantly being exchanged. Some environmental microbes are fleeting visitors, and some are long-term residents in our bodies.

Introduction to Microbiome Health & Human Health

The loss of microbial diversity associated with urban areas underpins the so-called “biodiversity hypothesis” which proposes a link between two global megatrends: 1) biodiversity loss and 2) a rapid increase in noncommunicable diseases (NCDs; e.g., diabetes, inflammatory bowel disease, and mental health problems). A growing number of studies support the biodiversity hypothesis. Evidence shows that the microbiomes associated with urban areas and urban lifestyles are suboptimal for health and well-being. The evidence spans different levels of empirical study, including human population-level studies, human cohort studies, and many animal model studies. Collectively, these studies support calls to conserve and restore biodiversity in our urban areas to enhance human health. This has the crucial co-benefit of supporting the other organisms who share the land with us.

The Importance of a healthy Microbiome in Cities

Interestingly, preliminary results also show that the relative abundance of pathogenic microbes (the few that can cause human diseases) significantly decreases when more trees and plants are present in the urban environment. All of this suggests that, if we increase the number of plant species and structural diversity (i.e., different shapes and sizes) in our urban areas, we will be exposed to a greater variety of beneficial microbes and to a reduced level of pathogens in the air. Therefore, ecological restoration can be viewed as a public health intervention. This means that bringing biodiversity into our cities is not only aesthetically pleasing and good for wildlife, but it is good for human health too.

This section is a primer on this topic. For more on the microbiome please go here.