Human bodies are like cities teeming with microcitizens—huge communities of viruses, fungi, and bacteria that live on our skin and inside us. Unsung public servants help us digest food, regulate our immune system, defend against pathogens, and keep hormones in check. Together they make up what we call the human microbiome.
Most people have probably heard of the gut microbiome, but different microbes thrive throughout our bodies—in our nostrils, on our feet, in our eyes. They are slightly different, as if the areas are made up of different communities of people. Ninety percent of the cells in our body are microbes. “clouds” of bacteria to move away from someone's body when they enter the room. We are all walking ecosystems, collecting and shedding material throughout our lives.
However, modern life is waging war against the ecosystems within and around us. When people think of a natural crisis, they probably think of the disappearance of tropical forests or species extinction, but there is another, hidden extinction that occurs at the microscopic level. At the same time we are losing species from our planet, we are also losing them inside our own bodies – with huge consequences for human health.
“What happens inside our bodies is a kind of reflection of what happens at the global ecosystem level,” says Anastasia Theodosiou from the School of Infection and Immunity at the University of Glasgow. “We increasingly think of it as an environmental narrative.”
There is already plenty of evidence that spending time outdoors is good for us: better physical health, cleaner air, less exposure to extreme heat. But growing body of research shows how amazing it is that not all green spaces are created equal: the diversity of life around us is linked to our own health.
Sometimes researchers call it outer and inner layers of biodiversity. The greater the diversity of species around us, the more beneficial microbes enter our body.
In urban environmentsThere are higher rates of inflammatory diseases, including allergies, asthma and type 1 diabetes. Today, fewer people are dying from infectious diseases, but the number of autoimmune diseases has increased, and “this is presumably due to the loss of microbes,” says Ina Schuppe Koistinen, an assistant professor at the Karolinska Institutet in Sweden. This idea is called the “biodiversity hypothesis” and it came about thanks to the Iron Curtain.
In the 1980s, a group of researchers studied differences in allergies between people living in Finnish and Russian Karelia who were genetically related. The Russian side was part of the Soviet Union with a subsistence economy, while the Finnish side was urbanized. The number of people with allergies was significantly higher in Finland, while in Russia asthma was rare and pollen and food allergies were virtually absent.
Karelian allergy study was the first to link less time spent in nature with an increase in health problems. Fast forward to today, and our disconnect from nature has become even more acute. Deforestation continues at an alarming ratewith more than 8 million hectares (20 million acres) destroyed last year. By 2050 about 70% It is expected that part of the world's population will live in urban areas. Reduced contact with nature has led to negative health effectsincluding a weaker immune system and increased rates of asthma and anxiety.
The destruction of the natural world also become the biggest driver infectious disease outbreaks as habitat loss forces people and wildlife into contact. A study published last month concluded that conservation of the Amazon forest will protect millions of people from disease.
However, just as these losses of people and ecosystems occur simultaneously, so too do the solutions work together. Last month a massive review of 1550 studies found that taking action to conserve biodiversity in cities has significant and wide-ranging benefits: improved physical and mental health, healthier child development, stronger social connections and less exposure to extreme heat, air pollution and noise pollution.
“The key takeaway is that if you take action to conserve urban biodiversity (by planting trees, improving park habitat, or creating green spaces), those actions are also likely to benefit human health,” says Erica Spotswood, a senior scientist at the San Francisco Estuary Institute and lead author of the paper published in the journal People and Nature.
“The potential for improvements in biodiversity and human health from taking action to create green cities is enormous,” says Spotswood.
Often when we increase people's encounters with nature, the results are immediate. Amazing study from Finland showed that just one month of growing the plants increased skin bacteria and the body's immune response. What was important was not the process of gardening itself, but the contact with healthy, biodiverse soil.
Microbiome research is proof of how intertwined our bodies are with the natural world. Every sip of food, the air we breathe, and the things we touch connect these two worlds. The desire to preserve the health of our own micro-citizens is another reason why people are demanding that we live more nature-rich lives and take urgent action to preserve a thriving natural world.
Find more Age of Extinction coverage hereand follow biodiversity reporters Phoebe Weston And Patrick Greenfield on the Guardian app to find out more about nature
