4 September 2024
This is the fourth of a series of posts on complexity. We’ll be exploring some of the ways that studying complex systems gives us a more nuanced way of understanding the world, how this is relevant to all our lives, and the unique contributions we can make to this new way of understanding the world from Aotearoa New Zealand.
The microbiome is the community of trillions of microorganisms living in, and on, the bodies of complex organisms – like people. In human beings this microbial community aids the digestion of food, supports the immune system, and protects us against pathogens – the infectious microbes that cause sickness and disease.
Do you think of yourself as a walking community of trillions of microorganisms? Probably not. Thinking of ourselves as individuals rather than a collection of microorganisms is an example of how we can classify the world into different scales.
Our knowledge systems tend to order everything into different scales to help us organise and understand our universe. These scales are typically used for convenience as well as having some meaning. It is useful to distinguish the individual from a population of people, just as it is helpful to differentiate days from years when we think of time scales.
The different levels at which a system can be observed or analysed
In complex systems, the concept of scale refers to the different levels at which a system can be observed or analysed. These levels can be thought of as micro, meso and macro. In the example of human beings, the microbiome is at the micro scale, the human individual at meso scale, and the natural and built environment that we inhabit at the macro scale.
These scales are groupings of size, but they are also sets of complex relationships which may be nested within each other. For example, interactions occur between the microbiome, the individual, and the environment. The composition of our microbiome is influenced by the food we eat, our habits and behaviours, which in turn are influenced by the natural and built environments we live in, in turn influencing those microbes themselves, which influences our health.
Understanding relationships between the system scales of the microbiome, the health of a person, and external environments is essential for knowing what to do to improve human health and prevent disease.
From the microscopic to the global, from the quantum to the cosmos
The planet that we live on is made up of interacting systems encompassing differing scales. These scales may be about size, place, organisation or time.
Spatial scales range from microscopic levels, like individual organisms or microhabitats, to broader landscapes and global ecosystems. Our universe ranges from the smallest known quantum scales to the entire cosmos.
Time scales encompass moments, seasons, years, and geological epochs, reflecting the dynamic nature of ecological processes over time from nerve impulses to annual seasonal changes in forests to the rise and fall of the large dinosaurs.
Organisational scales range from genes and individuals to populations, communities, and whole ecosystems.
Relationships between scales
Scales of any type do not have rigid boundaries. They are open systems that can be nested, interact with each other, and bonded by relationships that feed back and lead to emergent properties and adaptation.
A disruption at one scale can cause a cascade of interactions. For example, a pathogenic bacterial infection within a gut microbiome that causes disease is in reality a population of reproducing bacteria all interacting with other communities of viruses, bacteria and microorganisms – as well as the host’s own immune cells, and the non-living material inside the digestive system. The gut is an ecosystem within wider ecosystems.
Improving the health of human populations requires recognising relationships between scales. Even a very specific risk to health – like an infectious disease – has causes and impacts that will span multiple scales from the microscopic to the global. Think of the spreading and harm caused by SARS-CoV-2, the viral cause of Covid-19. The resultant pandemic showed that ignoring the ecosystem of relationships around individuals or communities not only reinforces existing patterns of harm, but reproduces harms over time.
Social scales also matter here. At the macro scale, the effectiveness of national health policies depend heavily on how they are implemented at the meso scale of local communities. Local health services that lack sufficient resources or fail to adapt to their local conditions can undermine national policy intentions. We saw this relationship in action through the Covid-19 pandemic where feedback from local Māori, Pacific and other community-led organisations – through advocacy and protest – influenced the national policy approach. This led to a faster reallocation of resources and development of more responsive and locally adapted communication strategies and health service delivery.
To understand our world, we need to look across scales
Understanding scales as systems of complex relationships helps to identify causes of phenomena such as, infectious disease spread, animal behaviour, human health or environmental degradation – but it also provides information about how we can intervene more effectively to create system change through human action that focuses on the relationships that link scales together.
To prepare for, respond to and learn from things like financial crises, natural disasters, systemic challenges to population health, or changes in the research system, we must look across the scales that influence individuals, communities, and all of humanity. This includes the connections between history, the present and the centennial and millennial time spans of collective memory.
To understand our world, we need to look across scales.
A collaboration between Te Pūnaha Matatini Principal Investigators Anna Matheson and Dave Hayman, and illustrator Hanna Breurkes. Edited by Jonathan Burgess.