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Home Biodiversity

Biologist Rob Dunn in his book Never Home Alone explains new research identifying about 200,000 species living in homes around the world. Most of these species are insects and micro-organisms such as bacteria and fungi. He writes: “More species of bacteria have been found in homes than there are species of birds and mammals on earth.” 


Most of the bacteria in homes pose no danger to us as these organisms live off the cells that continually die and float off our bodies and clothing. “We all fall apart at a rate of about fifty million flakes a day,” Dunn says. “Each flake floating through the air has thousands of bacteria living and feeding on it.”


Insects arrive as we enter and exit. Micro-organisms facilitating the digestive systems of our pets also take up residence.


Until recently, most humans spent most of their waking time outdoors, and their exposure to microbes on plants and animal species sustained the resilience of their immune systems. Now, however, most people spend only an hour or two a day outside. 

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What choices do we have to strengthen our immune systems? Our most important choice is not to try to cleanse our indoor environments by killing the insects and micro-organisms in our buildings. “The use of pesticides and microbials,” Dunn explains, “along with ongoing attempts to seal off homes from the rest of the world, tends to kill off and exclude beneficial species that are also susceptible to such assaults.” 

Also, “we unknowingly aid resistant species such as German cockroaches and bed bugs and deadly MSRA bacteria (the methicillin-resistant species of Staphylococcus aureus).” Trying to kill these resistant species actually “speeds their evolution.”


Why not increase biodiversity around your home? A diversity of plants will create an ecosystem with more Gammaproteobacteria that prevent skin allergies. These bacteria also thrive on food plants, so planting tomatoes, peas, beans, and root crops in your yard will strengthen your immune system.

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