Modern life is waging a war against ecosystems both around us and inside us, according to scientists who warn that a hidden extinction crisis is unfolding at a microscopic level within human bodies. As species vanish from the planet, we are also losing them from within our own microbiomes, with profound implications for health.
The human body is home to vast communities of viruses, fungi and bacteria that live on our skin and inside us. These microbes help digest food, regulate the immune system, defend against pathogens, and keep hormones in check. Ninety per cent of cells in our body are microbes, making each person a walking ecosystem that picks up and sheds material as they move through life.
Anastasia Theodosiou from the University of Glasgow says what is happening inside our bodies mirrors global ecosystem loss. “We are increasingly thinking about it as an ecological narrative,” she explains. A growing body of research shows that the diversity of life surrounding us is linked to our own health, with greater species richness bringing more healthy microbes to our bodies.
In urban environments, rates of inflammatory disorders such as allergies, asthma and type 1 diabetes are higher. Ina Schuppe Koistinen from the Karolinska Institute in Sweden notes that autoimmune diseases have increased, hypothesised to be related to the loss of microbes. This “biodiversity hypothesis” emerged from the Karelia Allergy Study, which found significantly higher allergies in urbanised Finnish Karelia compared to rural Russian Karelia, despite genetic similarities.
Our disconnection from nature has become more acute, with deforestation continuing at an alarming rate and 70% of the global population expected to live in urban areas by 2050. The reduction in contact with nature has negative health impacts, including weaker immune systems and increased rates of asthma and anxiety. Habitat loss also drives infectious disease outbreaks by forcing humans and wild animals into contact.
However, solutions work together. A recent review of 1,550 studies found that taking action for biodiversity in cities has wide-ranging benefits: better physical and mental health, healthier childhood development, stronger social connections, and less exposure to extreme heat, air pollution and noise pollution. Keeping our own microbes healthy is another reason to demand action to preserve the natural world.
