Several years ago, my editors at Audubon Magazine assigned me to write a story on native bees that took me to California to interview Professor Gordon Frankie, an expert on urban bee populations at the University of California-Berkeley. Dr. Frankie had become interested in studying urban bees after he was asked to identify bees from a census of a Berkeley-area park and was stunned by the number of species found, far more than he had expected.
What I learned from shadowing Frankie in a field workshop and in his urban bee garden on the Oxford Street farm at U-C Berkeley opened my eyes to the value of backyard wildlife habitat.
First, learning that there are more than 4,000 species of native bees on this continent—four thousand species!—introduced me to the astonishing diversity of native pollinators. I had no idea that there were so many kinds of bees that had evolved with North American flora, ranging from bees as tiny as the period on the end of this sentence to carpenter bees almost as long as my thumb. Nor did I realize that native bees were generally easy-going.
Frankie demonstrated the placid temperament characteristic of many native bees by plucking a foraging female out of a California poppy flower and dandling her—there is no other word to describe his gentle and affectionate handling—as she rolled over and groomed herself, seeming unfazed.
Nor did I realize how versatile and critical these native pollinators are to the survival of so many kinds of plants, domestic and wild. Some species, Frankie told me, have such a close relationship with one particular kind of plant that they are that plant’s only pollinator; without “their” bees, the plants produce few seeds, and are at risk of extinction. Sadly, many bees, Frankie said, were disappearing from wild lands and urban habitat alike, killed off by pesticides, habitat loss, introduced diseases, climate change, and competition with non-native species, including honeybees.
What really blew me away was when I asked Frankie what I as a home gardener could do to help native bee populations. “A plot [of bee-friendly plants] as small as 10 by 10 feet can help,” he said, explaining that he and his colleagues’ research pointed to such small areas of bee-friendly urban habitat as “refugia” for wild bee populations, harboring bee species that could repopulate adjacent wildlands and preserve genetic diversity. So he and his team had set up a website to help gardeners grow bee-friendly landscapes.
The idea of yards as “arks” that might actually preserve species was empowering–I had always thought in terms of bigger swaths of habitat. So I began designing urban landscaping projects with an eye toward providing critical habitat for native bees and other “little guys” that themselves support bigger wildlife from birds to bears.
But what about those bigger species, I wondered. Could backyard habitat somehow help their survival too? Censuses like Christmas bird counts showed that yards with native vegetation supported higher bird diversity than yards with non-native or exotic plantings. Now a new study published last month in the online science journal PLOS ONE gives the first quantitative data to support those observations.
In the study, researchers from U Mass-Amherst and Arizona State University used 24-hour video monitoring to measure foraging behavior of 14 common Sonoran Desert bird species in 20 urban yards, half with “xeric” plantings of largely native vegetation that mimicked the surrounding desert, and half with “mesic” landscaping including turfgrass lawns. Researchers measured foraging by placing trays in each yard filled with a specific amount of millet mixed into sand, and then timing how long birds spent searching for seed in the trays, as well as weighing how much seed remained when the birds quit foraging.
The results, say the researchers, show that birds in desert-type yards spent less time and energy foraging for seeds in the trays than birds did in the yards with lawns. It’s not that the xeric-yard birds spent less time feeding; they simply used the seed trays less because these yards offered more natural food.
That significant difference in foraging behavior is hard evidence, say researchers, of crucial differences in habitat quality. As the study synopsis concludes, “thus our study lends additional support for native landscapes to help reverse the loss of urban bird diversity.”
Imagine our yards as so many arks, providing habitat that helps reverse the loss of biodiversity. Imagine reconnecting with nature every day, right at home, and feeling good about our contribution to the health and beauty of this extraordinary Earth, the only home our species has ever known.
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