By: Gary Paul Nabhan
At dawn on this year’s spring equinox, a group of people gathered in Patagonia, Arizona, to declare the Sonoita Creek – Upper Santa Cruz River watershed the Pollinator Capital of the United States. An interpretive sign, erected in a pollinator garden on Patagonia’s village green, noted that hundreds of species of native bees, dozens of species of butterflies and moths, fourteen species of hummingbirds, and two species of nectar-feeding bats regularly frequent the native flowers in this semi-arid landscape. But the Patagonia community has not merely been interested in how much pollinator diversity has been recorded throughout this watershed. Its citizens and its nonprofit and for-profit organizations have joined forces to catalyze the Borderland Habitat Restoration Initiative, which aims to ensure a safer place for pollinators, their nectar sources, and, in the case of butterflies and moths, their larval host plants.
The rallying cry for this initiative is a deceptively simple-sounding phrase: “food chain restoration” (a synonym of the phrase “food web restoration,” which ecologist Andy Dobson has been employing for nearly a decade). When local resident and world-renowned ecologist Ron Pulliam began to employ this term to describe our work, he sought to emphasize that ecological food webs need to be restored from the bottom up, by reinitiating hydrological flows that will stimulate plants at the base of the food chain to flower and fruit. His working hypothesis is that certain habitats have a better chance of being fully restored by building food chains that support pollinators, frugivores (fruit-feeders), and herbivores, as well as predators, than they do by simply reintroducing “apex” predators, such as jaguars or wolves, which supposedly control ecosystems from the top down. But the term “food chain restoration” also resonates for me at another level. If we bring wild pollinators back into the wild edges of the working landscapes of farms, ranches, and orchards, it is likely that they will provide yield stability to cultivated crops, such as vegetables, legumes, fruits, and nuts, upon which our nation’s food security depends.
Pulliam is out to test his “bottom up” restoration hypothesis in a series of carefully designed ecological restoration experiments situated along the floodplains of Sonoita Creek and a tributary, Harshaw Creek. The phenology of newly planted pollinator-attracting shrubs is being monitored for the second year in a row, along with estimates of the intensity of floral visitation by pollinators. One goal is to determine how much influence these native shrub plantings have on the “background” pollinator fauna of the surrounding area.
At the same time, Caleb Weaver and I are adapting Pulliam’s monitoring protocols to determine the effects of hedgerows of pollinator-attracting native plants on pollinator abundance around fields, orchards, vineyards, and gardens in three Arizona counties along the border between the United States and Mexico. With funding from a USDA grant, we have helped farmers and orchard keepers plant twelve new hedgerows in southern Arizona, and many of these on-farm habitats have now been certified as “bee-friendly” food-producing landscapes by Partners for Sustainable Pollination.
It should come as no surprise to members of the Xerces Society that much of this work has been guided by staff members Mace Vaughan, Eric Lee-Mäder, and Brianna Borders. Vaughan’s lectures and workshops in the Southwest over the last two years have attracted scores of participants to this cause, and more than 120 volunteers have helped us plant pollinator-attracting hedgerows in the region. While it is still too early to gauge the extent to which these new plantings are affecting fruit and seed set for food crops, the survival rates and flowering activities of the native plants we’ve selected have been quite high.
Of course, these efforts are not merely about getting good numbers; they are also about reinvigorating curiosity and wonder about pollinators among the Southwest region’s residents and eco-tourists, both young and old. This summer, an Earth Care Youth Corps of six teenagers helped to collect milkweed pods, build nurseries, and sow seeds of the twenty species of milkweed (Asclepias) that occur in Santa Cruz County, Arizona. The students learned about the importance of milkweeds to monarch (Danaus plexippus), queen (D. gilippus), and soldier (D. ereisimus) butterflies that frequent their home neighborhoods, and about threats to monarchs as well. We hope that they have taken back to their high schools a deeper understanding of the monarchs on their migration through the region and pride in the fact that they live in one of the most diverse milkweed communities in the entire country.
These three butterflies in the genus Danaus are but a small part of the extraordinarily rich fauna of Santa Cruz County, which, over the years, has attracted exploration and documentation by the likes of lepidopterists Richard Bailowitz, Jim Brock, Kilian Roever, and Ken Davenport. At least 135 of the 240 species of butterflies known from southeastern Arizona occur along Sonoita Creek and its tributaries, some of which reach into the United States only within this watershed. These include the giant swallowtail (Papilio cresphontes), the sachem skipper (Atalopedes campestris), the gulf fritillary (Agraulis vanilla), and the West Coast lady (Vanessa annabella), which are widespread but not abundant in the region, as well as the regionally rare Mexican fritillary (Euptoieta hegesia). The elf (Microtia elva) and the aforementioned soldier butterfly are occasional immigrants to the watershed.
By propagating, transplanting, and protecting the nectar and larval host plants for many of these species in our pollinator gardens and on-farm hedgerows, we have already witnessed an increase in the local abundance of butterflies such as the pipevine swallowtail (Battus philenor), which remains active twelve months a year in this area. Our attention to larval host plants as well as nectar and roosting sources for butterflies is making our planning of additional hedgerows and pollinator gardens more complex but also much more rewarding. Already, we are developing a trail along the village green from a new “generalist” pollinator garden to an older butterfly garden in Patagonia, and we are planning a hawk moth garden, a bat garden, and a hummingbird garden along a walkway that leads to the community’s vegetable garden. All will have interpretive signs that remind visitors of the diversity of pollinators in this special place and explain their ultimate importance to our food security.
The bee fauna of Sonoita Creek has been considered by such entomologists as Stephen Buchmann, D. P. Hurd, and E. G. Lindsley to be just as exciting as the butterflies; more than six hundred species of bees are native to southern Arizona. The all-yellow Morrison’s bumble bee (Bombus morrisoni) and the large, striped Sonoran bumble bee (B. pensylvanicus sonorus, one of the target species for Xerces’ Project Bumble Bee) frequent the watershed, as do four genera of sweat bees and two genera of squash and gourd bees. By constructing fences of dead flower stalks of century plants and the shrub known as desert spoon, we have increased the local abundance of large carpenter bees (Xylocopa). On the edges of the same orchards and fields, our plantings of buffalo gourds, coyote gourds, and devil’s claw have attracted smaller bees that are far more loyal to certain crops and their wild relatives than is their naturalized competitor, the European honey bee.
The habitat restorationists and agro-ecologists involved in our projects have been rewarded to learn that sociological surveys of southern Arizonans indicate a great deal of interest in sustaining populations of pollinators of all kinds. A growing number of people in the regional business community recognize that the presence of so many kinds of hummingbirds and butterflies is vital to the ecotourism activities that provide significant revenues to rural populations. And they are just as aware that if native bees suffer further declines, the farming and ranching economies of the region might be adversely affected.
These perceptions have bolstered our hope that food chain restoration can help to generate a true “restoration economy” for the now-impoverished borderlands region, one in which new jobs on farms, in native plant nurseries, and at nature-tourism destinations would be most welcome. Our vision is that the return of formerly forgotten pollinators will not only curb the ongoing extinction of ecological relationships that plagues the continent today, but will also return economic health and well-being to the rural communities along the border that choose to be good stewards of such relationships.
Gary Paul Nabhan, an advisor to the Borderlands Habitat Restoration Initiative, holds the W. K. Kellogg Endowed Chair in Sustainable Food Systems at the University of Arizona. His books include The Forgotten Polinators (with Stephen Buchmann), Conservation of Migratory Pollinators and Their Nectar Corridors in Western North America, and the newly released Growing Food in a Hotter, Drier Land.