Is it good to have high bacterial diversity on my skin?

What is diversity? It’s a measure of the number of species present in an ecosystem. Ecosystems that contain a higher number of species are more diverse. This lesson should provide you with an understanding of how diversity affects your skin.

Please watch the video below before continuing.

Picture two ecosystems – one is diverse and there are thousands of different plant species per square kilometre – let’s say it’s a tropical rainforest. The other is a monoculture – perhaps a wheat field. Now introduce change, for example, a sudden drop in rainfall and a rise in temperature.

In a diverse ecosystem, some species may die, but others will thrive in the new conditions – the ecosystem will shift, but it will remain vibrant and functional. In contrast, the monoculture dies, and you are left with a field of sparse weeds. Diversity will slowly creep back if the system is left alone, but it will take a long time and in the interim, opportunistic species rule. In a monoculture, there is no framework for close, interdependent relationships between species. A diverse ecosystem is a healthy, robust ecosystem.

In the same way that diversity provides long-term stability and resilience in a rainforest, so it does on the skin. Having a diverse microbiome offers protection against changes and pathogens, keeping your microbial ecosystem healthy and functional.

Human skin is a unique environment, and in its healthy state, it supports a very specific group of microbes – those that have co-evolved with us, developing to fill the specific niches in this unique ecosystem. Unfortunately, our adoption of a western lifestyle has resulted in a vast reduction of microbial species on our skin.

We have lost around a third of our microbial diversity in comparison to a hunter-gatherer community. The microbes we’ve lost were functional parts of our skin’s ecology, and their loss represents significant damage to our microbial ecosystems.

Unfortunately, we cannot replace this diversity with just any microbes. For example, the microbes in a sewer may be diverse, but we do not want them on our skin. Diversity is only beneficial if it is within the very tight subset of microbes that have co-evolved with human skin. So, the damage done by our lifestyles can’t be undone by simply seeking diversity from elsewhere.

We have seen on a macro-scale that when we destroy an ecosystem, it is very difficult to reinstate. We can replant the key tree species in a damaged forest (and this is already a difficult task), but what about the pollinators and seed-dispersing animals that ensured the long-term stability of these tree populations?

Ecosystems are deeply complex and modelling the thousands of interactions between species is beyond the capacity of humans and computers. It is now becoming apparent that it is going to be extremely difficult to restore key members of our own ecosystems. We need to retain the diversity of our uniquely co-evolved microbes.