The health of an ecosystem (including your home) depends on its biodiversity

William Foster writes:

Rob Dunn invites us on a safari in pursuit of the wildlife teeming on our bodies and in every corner of our homes. For him, the creatures that sprawl in the human navel and under the bathroom shower head elicit the kind of wonder most of us would feel only on seeing the denizens of Tanzania’s Ngorongoro Crater or the Great Barrier Reef off Australia. Dunn is more than an informed and entertaining commentator, a David Attenborough of domestic biodiversity. He is a scientist whose research group at North Carolina State University in Raleigh made many of the discoveries described in his fascinating and illuminating book, Never Home Alone.

Dunn and his colleagues have used the concepts and techniques of community ecology to tease apart the functioning of a mostly ignored ecosystem: the human home. Their research enriches our understanding of ecosystem function, and — more grippingly — gives us insight into how our interactions with living things in the domestic habitat affect our health and well-being. The book is structured around sub-habitats in our homes — our bodies, rooms, water supply, pets and food. It considers an awesome range of organisms, from the rich fungal flora on bakers’ hands to the diversity of fly larvae in our drains.

We discover that warm, moist shower heads are ideal for the growth of biofilms containing trillions of bacteria, including Mycobacterium species that are harmful to human health. Dunn and his colleagues invited thousands of volunteers globally to send in samples from their bathrooms. The researchers are finding, for instance, that the more a water supply is treated with chemicals designed to kill microbes, the greater the abundance of pathogenic strains of mycobacteria. We also learn that the numbers of plant and butterfly species in our gardens are correlated with the robustness of the community of microbes on our skin; that some German cockroaches have evolved to perceive glucose as bitter, thus avoiding poisoned bait; and that dogs can give us both heartworm and a top-up of beneficial bacteria from their microbiomes.

The message of Never Home Alone is clear. The health of an ecosystem depends on its biodiversity: this is as true of our homes as of a mangrove swamp. Two factors, notes Dunn, are important. Simply by chance, a home containing more species is more likely to include organisms (especially microbes) that are vital in sparking our immune systems into life. And an ecosystem with niches fully occupied by diverse species is likely to be resilient and resistant to invasion by pests and pathogens. [Continue reading…]

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