Pollinators – bees, butterflies, moths, wasps, flies, beetles, ants, bats, hummingbirds and others – are a vital component of the planet’s ecosystems. Almost 90% of all flowering plants and more than a third of the world’s crop species depend on them. Countless species of birds and mammals feed on fruits and seeds that couldn’t exist without them. With pollinator populations in steep decline, it is becoming ever more crucial to ensure that these imperiled creatures have safe havens in which to thrive.
Through the smart use of so-called “green infrastructure,” the same urban landscapes that are eating up wildlife habitats with such devastating effects also present opportunities to create those havens.
Green infrastructure can take many forms, from street trees to green stormwater infrastructure like the bioswales and rain gardens now used in many cities to manage stormwater runoff and mitigate flooding. Much of this infrastructure can double as wildlife habitat, and some can be particularly beneficial to pollinators.
Living roofs
While each species has its own specific habitat needs, there are two that are common to all pollinators: an abundance of diverse, flowering native or naturalized plants, and safe places to nest and breed. Among the most effective (and cost-effective) forms of nature-based urban infrastructure in meeting these needs are “living roofs” or “rooftop meadows” planted with wildflowers and native grasses and/or other native or naturalized pollinator-friendly plant species.
High above the city streets, even in the densest urban settings, these hotbeds of biodiversity can support all kinds of pollinators, from bees and butterflies to birds, bats, flies and ants. Studies have found that they can be particularly valuable to bees, especially when planted with diverse native forbs (flowering, non-grassy herbaceous plants) to provide foraging resources and designed to take into account the differing nesting habits of different bee species. (Interestingly, research has also suggested that living roofs can also enhance the performance of rooftop solar panels.)
Where living roofs have been planted to restore lost pollinator habitat, the results have often been quite extraordinary. The six-acre roof meadow of the Vancouver Convention Center, for example – “the only and largest coastal meadow” in downtown Vancouver – is planted with more than 400,000 indigenous plants and grasses, providing habitat for birds, insects and other creatures. Since it was built in 2009, 250 types of insects have been seen on the roof, including two species of pollinator previously thought to be extinct in the Vancouver metro area.
Green walls
Natural elements can be incorporated into building design in numerous other ways. “Living walls,” for example, can host a wide range of different plants, from grasses, shrubs, ferns, succulents and herbaceous plants to all manner of vegetables and herbs, and when designed with the needs of specific species in mind, can potentially be a promising pollinator habitat.
Living walls - also known as “green walls”, vertical greening systems, vertical gardens, or biowalls – are among the least tried and tested forms of green infrastructure, but research suggests they have potential to provide pollinators with important sources of forage and shelter – and to do so without conflicting with human demands for space in cities.
The space on a building that could be used for green walls could be as much as double that of the ground space that that building occupies, meaning existing urban architecture could be a huge untapped resource for creating pollinator habitat. There are two basic kinds of green walls: “green facades,” which use hanging plants or climbing plants rooted in planters or in the ground, and “living walls,” where plants are rooted in the wall itself, kind of like the vertical equivalent of living roofs. This means they can host a much greater range of plants and flowers, making them especially promising for pollinator conservation.
Living walls are still very much an emerging technology, but there's already a growing list of examples to draw from. Three thousand square feet of living wall on Los Angeles’ Santa Monica Boulevard, known as the “Living Billboard,” has proved attractive to pollinators like hummingbirds. UK retail giant Marks & Spencer has been installing living walls on its stores for years. Almost 3,000 square feet of wall at London’s famous Wimbledon tennis courts are home to more than 14,000 plants, and the spectacular facades of the Athenaeum Hotel and Residences and The Rubens at the Palace in London provide habitat to butterflies, bees, birds and other wildlife, as do similar structures at Liberty Park at the World Trade Center in New York, the Musée du Quai Branly in Paris and numerous others all over the world.
Native landscaping
Roadsides present a huge opportunity to transform municipal infrastructure to support pollinators. The U.S. has more than 4 million miles of roadway, and much of the land alongside those roads can easily be planted with native vegetation and flowers and provide a valuable refuge in which pollinator species can nest and breed. Strategies like roadside wildflower planting, planting pollinator host plants in public parks and other municipal land, and providing resources for homeowners to convert yards and street-facing margins from turf to native landscapes, are easy wins for pollinator-friendly green infrastructure.
The strips of ground between the road and the sidewalk – known in California as parkways, and elsewhere as curb strips, tree lawns, “devil strips” and various other names – are pollinator habitat waiting to happen. Often these areas are technically city property but the responsibility of individual homeowners to maintain, and this provides an opportunity for residents and city authorities to work together to create native habitats that can provide crucial sources of nourishment and shelter for pollinator species.
Some cities already offer programs to provide native plants and other resources for homeowners looking to convert their parkways to native habitat. The expansion of these kinds of schemes nationwide could give a major boost to citizen involvement in creating safe spaces for the bees, butterflies and other creatures that exist as an essential, yet often neglected component of natural ecosystems.
Encouraging pollinator-friendly development
City and state authorities are going to need to up their green infrastructure game over the coming years for a whole range of reasons
besides helping pollinators. But to the greatest extent possible, and
where appropriate, that infrastructure should be conceived so as to
incorporate pollinator-friendly habitat.
Local agencies can lead
by example, from installing green roofs and walls on municipal buildings
to transforming roadsides into pollinator habitat and implementing
other citywide initiatives to weave pollinator-friendly living elements
into the urban fabric across other publicly managed green spaces.
Policymakers can also use various legislative carrots and sticks to ensure that provisions for native pollinators are incorporated into future development. Some cities, for example, like Austin and Portland, have revised their zoning laws to give “density bonuses” or other zoning incentives to developers who incorporate living roofs into new construction projects. Other cities offer discounts on stormwater fees or provide tax incentives to developers installing green roofs, as is the case in Washington, D.C. A growing number of cities – Toronto, San Francisco and Copenhagen, among others – have gone further, passing legislation mandating the installation of green roofs on all new buildings and renovations.
Increased attention to the importance of pollinators has led to an increase in new sources of government funding being made available to expand their habitat, including funding specifically for the kinds of programs discussed above. In the U.S., the Infrastructure Investment and Jobs Act (IIJA) provides a total of $10 million to be distributed via the DOT to states, tribes and federal agencies to implement measures to restore pollinator habitat along roadways, for example, such as planting native wildflowers and grasses, removing non-native vegetation, and adopting pollinator-friendly land management practices designed to promote pollinator host plants and limit disturbance during periods of highest use by specific species.
Just as the urban world must strive to provide a livable habitat for its human populations, it can, and must, provide an environment in which its non-human residents can thrive. With targeted investment and proper attention to the growing body of science on the integration of nature into urban design, the cities of the 21st century can play their part in helping our beleaguered pollinators bounce back.
