The Need
One out of three bites, that’s what we owe to pollinators for our diet. Most plant species, over 90% by some estimates, rely on animal pollinators for seed reproduction. Consequently, food, sustainable plant reproduction, and many other ecological services of plants that restorationists tout must lead our community to being grateful to bees for their labors. Yup, they really are busy. Yet keeping bees in our restoration world is not easy. Most people in the world live in cities and the usefulness of plant communities providing food and habitat advantages is often difficult to communicate. Also, the physical structure of cities and the attitudes of urban residents are two high hurdles for the effective restoration of pollinators to climb.
The Bee Community
There are over 4,000 bee species in North America and hundreds of species can live within our major cities’ borders. Most people perceive honeybees and bumblebees as the pollinators around them but the large majority of the species are small and solitary; these are the ones that visit most of our flowering species. Often colorful and always with intricate life history requirements, the small bees vary in their floral preferences, nesting requirements, and foraging skills. Some bee species are wide generalists and will visit many flower types over the seasons. Others are narrow specialists and will visit only one or a few closely related plants during their short lives. In an old-field community, dozens of bee species appear and disappear over a growing season, timing their work to the sequential opening of flowering species after species. For a sustainable pollinator community, a restoration ecologist must provide a succession of flowering phenologies to provide nectar and pollen for the bee community as well as a real estate office’s worth of habitats to supply the required breeding sites for this group. It is so difficult just to define, purchase, and install the plant community. Equal attention is needed to secure our pollinators. The plant palette can be purchased from many native plant nurseries, but don’t go looking in Home Depot aisles for bee species. They must naturally colonize your site from the wider landscape, and this may be a slow process.
The Sting: The Human Community Strikes Back
Even when one does secure a functioning diversity of bee species, the shadow of human anxiety soon darkens this accomplishment. The fear of stinging insects is intense, no surprise, and bees are usually filed away in the category labelled dangerous, not beneficial. Bee specialists exhaust themselves explaining the reality: only females have stings, half the bees are morphologically harmless; the bees are plant eaters, not carnivores, and don’t look to us as something to chew on; we are giants to bees, their habitat’s Godzillas, and they probably fear us more than we fear them. In we come and away they go.
One conservationist, David Tallamy, told me he often does not like to use the word “insect” because this elicits avoidance and fear. He much prefers to say “bird food” because people want birds in their yards. Another land manager from Reston, Virginia, Claudia Thompson-Diehl, once told me she mows the hiking paths through her meadows 2m wide, much wider than needed, just to make sure that stems don’t brush up against visitors’ legs. To many, a stem on the leg means a biting insect might land on you and give you a deadly disease. With her wider paths, visitation to her projects has gone way up. We do not dismiss the human behavior of risk avoidance as foolish. People magnify risks when their potential danger is unknown, and getting people and pollinators to hang out together is like having a dating website that nobody visits. No “OkCupid” for these Hymenoptera and us, sorry.
The Limits
Restoration practice is constrained from achieving historic biodiversity in many ways. Supporting the bee community, with its subtle diversity of niche requirements and often short flight distances, is a particularly difficult Gordian knot to untangle. The scale of our projects is often small, denying us landscape space where bees can find appropriate and diverse nesting and foraging resources. The adjacent areas to our projects might be housing developments, paved parking lots, or interstate highway; none of these represents rich habitats from which a biodiverse fauna can colonize. They are invertebrate poorhouses. In urban projects, an enormous wall of tall buildings and other infrastructure can become mazes within which the cleverest Hymenoptera can easily be lost when searching for nearby green spaces.
Our planting schemes also may be unfavorable to sustaining a species-rich bee community. There are many factors in determining which plant species to include in a landscape palette. After finding native species that are appropriate for the soil conditions and local microclimate, the practitioner thinks about aesthetics, persistence, management, and resistance to herbivores. A sequential flowering phenology may be difficult to add as a requirement for the plant species list even when that flowering pattern is recognized as ecologically valuable. The affection of the site owner for butterflies over bees is so common that plant species chosen may be focused on Lepidoptera and their life history needs while leaving Hymenoptera requirements a distant second, insect wallflowers at our habitat party.
Studies have shown the relatively poor foraging value of many cultivated varieties of wildflower species. The horticultural industry often selects for large flowers and deep colors as compared to the native, wild type, varieties. These nursery selections do not emphasize volume of nectar produced per flower even though that is the critical attraction to the bee community, albeit not to the “hi-honey-let’s-pick-a-floral-arrangement” crowd. (Nothing against bouquets.) Attention must be paid in project specifications and functional ecology criteria for the best provisioning floral varieties for the pollinator guild so that our plant communities become sustainable with adequate seed set.
The structure of our restored habitats is a mosaic of sun and shade patches with light shafts flickering through the landscape at different times of the day. This light pattern yield patches of warmer and cooler locations which slowly dance across the habitat as the sun moves. Some very clever research has shown that these warmer routes entrain pollinators to go from one flower to the next flowers that are in the spotlight of a sun shaft; the insects do not fly randomly throughout the whole site. Consequently, pollinator service, seed set, and regeneration potential are patterned by this illuminated pathway, a subtle level of restoration design that is almost impossible to achieve. Our plant populations enlarge not in concentric waves but as a function of a complex interspecific/spatial interaction.
Finally, the microsites for bee nesting in our projects are also diverse, including soil tunnels, hollow plant stems, abandoned mouse holes, and mud constructions. These nesting sites appear and disappear over the history of a restoration. Small locations with open soil and soils of varying textures are particularly important but not always available. An erosion gulley was once identified as a prime bee nesting site in an urban project, great excitement about the number of pollinators living there. However, an erosion gulley is an engineering failure as well as an ecological advantage, and the management crew quickly patched and replanted with perennial grasses, erosion deterrents. The favorableness of the site for bees was erased. Gentle complaints to the land manager were met with, “Bees, you want bees? Who wants bees? Erosion areas are required to be filled under state law.”
We don’t want to drone on about these bee problems. We present, yet again, the delicious stew of issues that the restorationist must confront: obscure invertebrates are critical for ecological function, but needed microsites and other bee species-specific resources are hard to design or obtain. Every successful restoration action butts up against human ecology and the fear of nature. “Too be or not to be” may be a quandary for our human fate, but to our living landscapes’ fate, bees are not optional; they are a functional requirement.
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