Highways Can Help Pollinators Return to Health

Compost-spreading tactics to encourage native plants that both control erosion and attract pollinators / Caltrans

In the face of rapidly-declining honeybee populations, farms across the country are under threat. In California, officials are now pioneering new methods to boost the health of the honeybees and butterflies, according to a recent Congressional hearing in Washington, D.C. To reiterate the importance of these efforts, Congressman Jeff Denham, who is also an almond farmer, said at the briefing: “making sure we have healthy pollinators is critical to a state like California.”

There to discuss these pioneering methods was Keith Robinson, ASLA, principal of the landscape architecture program at the California Department of Transportation (Caltrans). The purview of Robinson and the 240 landscape architects he leads is roadsides. Their primary job is to control erosion. But Robinson and his team have seized on that mandate to boost the health of pollinators along California’s 250,000 acres of highway roadside.

Robinson said it all starts with the soil. “We are prioritizing the improvement of soil quality on every single project. We want to make sure that soil sustains native plants and creates favorable conditions that encourage pollinator plants to not only to grow but thrive.”

Robinson’s team began this effort by performing studies on the optimal amount of compost that can be included in the soil. Compost “gets things moving along, and then the natural process takes over.” The right amount of compost allows native species to out-compete non-natives, foregoing the need for many herbicides that might negatively impact pollinators. Robinson’s team realized they could use Caltrans’ often-idle snow blowers to spread compost.

Another innovative step taken by Robinson’s team was the development of native grass sod, or pre-packaged grass carpet. “With native grass, the thinking was you can’t cut the roots and expect the plant to grow. But we’ve proved that it works.” Native grasses not only help erosion control, they encourage pollinators. “If you compare this solution to what we used to do, which was put straw down on top of compacted soil and hope for the best, you can see we’re moving down a path towards natural solutions,” Robinson said.

In addition to these steps, Caltrans ramped up planting pollinator-friendly plant species along highways. TransPLANT, an online tool, helps landscape architects choose sustainable, pollinator-friendly plants for their own projects.

Whether these effort can benefit pollinators fast enough is unknown. Robinson noted no studies have been performed on pollinator habitat health in state highway rights-of-way. And a recent study done by the Xerces Society for Invertebrate Conservation found that monarch butterfly populations in California have declined 74 percent in the past two decades.

Monarch butterfly /
Monarch butterfly / Public Domain Pictures.net

Another speaker, Eric Silva, American Honey Producers Association, expressed resignation that reversing the trend on bee populations was a losing battle. “We’re losing half the bees over the course of the year.” The environmental culprits are relatively well-known: pesticides and chemicals, habitat loss, and pests.

Robinson offered hope for the future. His team has developed an online roadside management toolbox that helps other transportation departments learn from Caltrans’ methods. The site has tens of thousands of visitors in the U.S., but has also gotten healthy traffic from countries such as India and Canada.

And regarding the future of roadside planting, Robinson envisions hyper-local roadside ecosystems that include native as well as non-native, well-adapted species. “The pollinator and native plant advocates have voiced their appreciation for our efforts,” Robinson added. “I don’t think the public is as aware of what we are doing yet.”

6 thoughts on “Highways Can Help Pollinators Return to Health

  1. DL 07/13/2016 / 2:49 pm

    Sounds like an interesting project. I must say though, I don’t think it is the highway that is helping as much as reclaiming the median strips. It would be interesting to know what kinds of pollinators end up using this type of habitat. Generally roads and non-human life don’t seem to go that well together. Highways are known for facilitating the spread of invasive species and reducing habitat connectivity, for example. I suppose if they are amending the soil with compost, they are also adding some sort of carbon source as well? Regardless of what the potential benefit to insects may or may not be, it’s very encouraging to see native plants being used in transportation projects.

  2. Benjamin 07/18/2016 / 8:20 am

    First, we do not need honey bees. We’ve simply created an agricultural system where we rely on them — without addressing the system that burdens these managed bees the conversation is focusing on the wrong level. Further, what we need are the 4,000 species of native bees, who collectively far outshine European honey bees in pollination and ecosystem services. The more bee diversity we have, the better our crop yields, fruit set, fruit quality — but this means more habitat. That habitat will also support beneficial predator bugs and birds, which can lessen the need to pesticides.

  3. John Nicolaus, FASLA 07/20/2016 / 11:53 am

    Finally: some uplifting news regarding California’s misbegotten roadside landscapes. Now dead and dying, seeing at least SOMETHING happen is cause for celebration. Plant on! And irrigate legacy trees to prevent further decline of important community and state assets.

  4. R. Gus Drum 07/20/2016 / 12:03 pm

    Unfortunately interstate highway medians and roadsides have long been the graveyard of many butterflies and bees of all types since the interstate system started. None of these species has the ability to fly around, over, or beneath vehicles traveling at 70 mph and end up in grills and windshields. Enticing these flyers into a kill-zone with flowers may do more harm than good. There are other landscapes that are safer for pollinators where these types of threats do not exist….cemeteries, golf courses, parks, reclaimed mine sites, reclaimed solid waste disposal areas, etc. Or as an alternative restrict these types of roadside plantings to roads with traditionally low speeds.

  5. Laura K 07/23/2016 / 1:45 am

    So happy to hear a trend towards foregoing the spraying of poisons by Caltrans! You are pioneering the future of the roadways which includes the health of the animals, insects and humans who live adjacent to the roads and we thank you!

    We would love to see an adopt a highway program so communities like mine can manage roadsides ourselves without the use of poisons and sprays. Our roadways are covered with native plants that are used by pollinators, bees and by butterflies and moths for food and egg laying. These delicate populations rely on our good sense to protect them so the fabric of life isn’t missing this important element needed for the survival of the human race. Thank you for being part of the solution.

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