The story of Coastal Douglas-fir forests: Plant-pollinator communities and connections

Ecosystems are just that, systems, founded on countless connections and relationships developed over centuries that keep everything in balance. Pollinators play a vital role in these systems, but loss of native plant diversity due to development and myriad other pressures reduces pollinator diversity, which in turn exacerbates the decline of native plants, creating a negative feedback loop that results in the homogenization of once diverse and abundant landscapes.

Dr. Lora Morandin, Research and Conservation Director for Pollinator Partnership and Pollinator Partnership Canada, highlights the importance of pollinators in the CDF and supplies recommendations for how to support them.

What role do pollinators play in maintaining diversity within the Coastal Douglas-fir zone?

Around 90% of flowering plants need pollinators to reproduce sexually—that is, to produce the seeds that turn into new plants and the fruits that wildlife eat. The pollinators of Coastal Douglas-fir (CDF) ecosystems are intimately connected to all the other life these places support. 

The many early-flowering spring herbaceous plants and shrubs in the shady understory, and in the more open rocky areas, depend on, and provide pollen and nectar to the early emerging native bees such as miner bees, mason bees, and queen bumble bees. These plants include June plum, shooting star, fawn lily, spring gold, and sea blush to name just a few. Additionally, moths and butterflies, beetles, flower flies, and solitary wasps use the resources these plants offer and provide pollination so that the plants can reproduce. 

Later in the spring, and in the early summer, other species of native bees and pollinators emerge and rely on the shrubs and herbaceous flowers that bloom during this period such as woolly sunflower, camas, blue-eyed Mary, and Saskatoon berry. As the summer progresses and turns to autumn, plants such as gumweed, asters, yarrow, and goldenrod provide the food needed by pollinators and they in turn benefit from the diverse community of native bees, butterflies, wasps, and flies that visit them. 

Variation in the ecosystem is very important for supporting a diverse community of pollinators. For example, some native bees like to nest in the ground or in above-ground vegetation under shady, closed canopies, but then take trips to sunny meadows to forage. These intricate plant-pollinator relationships have evolved over thousands and hundreds of thousands of years, resulting in connections that rely on healthy and diverse ecosystems, and networks that are timed with the seasons and climate. 

Loss of CDF ecosystems accompanied by a changing climate has decimated these relationships. Beyond the loss of plant-pollinator communities and connections, entire ecosystems can collapse when pollinator populations become less diverse and abundant. The seeds and berries that many wildlife rely on are no longer available; pollinators–which  themselves are food for many wildlife–are vastly reduced in numbers; and plants have to rely more on asexual reproduction (such as rhizomes) which doesn’t allow them to adapt as well to the changing climate. Some plants are able to survive without pollinators, and those plants will tend to take over areas where pollinator populations are lacking diversity and abundance, resulting in ‘homogenization’ of lands, that is, lands that have fewer types of plants, fungi, animals, protists, and bacteria. 

What impact have invasive species had on CDF ecosystems? 

Invasive, non-native plants have been brought to our area, both intentionally and accidentally, and have had a devastating effect on CDF ecosystems. Having evolved elsewhere where they developed relationships with accompanying plant and animal species over hundreds if not thousands of years, these introduced species are often able to proliferate in their new environment with few animals or other organisms to keep them in check. With this release from the ‘enemies’ they evolved with in their native range, they can have a competitive advantage over the native vegetation that supports and is utilized by native wildlife. 

For pollinators, incursion of non-native, invasive plants into CDF has resulted in a loss of many of the floral resources the pollinators rely on. English ivy, blanketing forest floors, chokes out the diversity of flowers that would have bloomed from early spring into summer. Scotch broom, which is native to Europe and North Africa, was introduced as an ornamental plant in California in the 1850s. It invades native meadows, changing the structure of the meadow to a shrubbier ecosystem, forming monocultures that crowd out other vegetation. It also enhances the nitrogen in the soil and increases soil acidity, negatively impacting some of the native plants that are adapted to lower nitrogen and less acidic soils. Scotch broom and other invasive plants such as Himalayan blackberry may look pretty and provide short-lived resources to some pollinators, but, for the most part, these plants provide resources to only the generalist pollinators (those that can access resources from many plant types; bumble bees are generalist pollinators). In addition, they crowd out other plants and their pollen and nectar is only available for a short time. 

By only supporting a subset of our native pollinators for a short timespan, and directly causing a reduction in native plants, invasive plants are in no way beneficial in CDF ecosystems. Concerted effort to remove these species and educate the public on their harm will go a long way towards reducing their negative impact. Further, getting these plants out of garden centres and seed mixes is essential for slowing the spread of current invasive species and reducing new types of invasive plants that may become a problem in the future. 

Is there anything individuals can do to help foster biodiversity in this region?

Individuals can play a large role in helping to foster biodiversity in our region. Much of the area that was once CDF is now privately owned land. A great way to support biodiversity is to start using native plants in your own yard and removing any plants that are invasive in our region. It may not seem like a lot, but in my yard, by slowly adding a few native plants each year, I’ve created an ecosystem that is far more diverse, interesting, and beautiful than it was before making these additions. 

The woolly sunflower in my front yard gets visited by green metallic sweat bees (one of my favourite native bees!), long-horned bees, swallowtail butterflies, and many other solitary native bees and pollinators. The flower flies that visit the yarrow that has spread from my garden beds to graveled areas lay their eggs on my garden plants. These flower fly eggs hatch into larvae on my vegetable plants and eat the aphids that would otherwise become problematic. Birds visit in the summer and fall to eat twinberries and Oregon grape berries that the pollinators have helped to produce. In late summer and fall, the goldenrod in my front yard has spread throughout the garden bed without any care or supplemental water. It supports so many species of native bees and butterflies that I am often late for appointments during bloom time as I need to stop and watch the diversity as I leave my house! 

Small areas that are ‘rewilded’ in yards can make a huge difference. Imagine the change if most yards in your neighbourhood were enhanced even just a bit with native plants. Putting up signs in your habitat can help your neighbours learn about what you are doing and inspire others to plant for biodiversity. There is a common misconception that planting for biodiversity can mean sacrificing aesthetics. That is far from true.  Native plants are beautiful, easy to maintain, and can provide food and medicine in addition to their biodiversity value. For example, instead of planting highly invasive Daphne laurel, one might plant evergreen huckleberry which produces showy bundles of pink, bell-shaped flowers in the spring and bunches of rich purple berries in the fall, which can last well into the winter providing an important food source for non-migratory birds. The Invasive Species Council of BC’s Plant Me Instead Guide provides myriad recommendations for replacing invasive species with beautiful native counterparts for those seeking to rewild their gardens . 

Beyond rewilding your yard, there are many other ways to support pollinators and biodiversity in our region: 

• Join a volunteer group that removes invasive plants from your local park.
• Keep your dog out of areas that are fenced off or where it has been indicated that there is rehabilitation underway and/or sensitive native plants present.
• Learn about native plants and pollinators.
• Support groups that are working to preserve remnant habitat and rewild disturbed areas.
• Ask for native plants at garden centres so that they will begin to stock them.
• Talk to your local municipality about using native plants for their landscaping. 
• If you are part of an industry or company that owns land that could be better used to support biodiversity, become a champion for change; talk to your company about how you could better manage your land in ways that support biodiversity.

Individual actions can make a big difference to biodiversity support, and if many individuals act, we can make a large difference to the unique animals, plants, fungi, protists, and bacteria that thrived here prior to colonization.  

About Lora Morandin

Dr. Lora Morandin has a Ph.D. from Simon Fraser University in ecosystem biology and conducted post-doctoral research at UC Berkeley. Her research focuses on how pollinators and biodiversity support can be integrated with human land-use. She currently is the Research and Conservation Director for Pollinator Partnership and Pollinator Partnership Canada and is involved in research, habitat creation, policy advising, and industry consultation across North America. She created the Pollinator Steward Certification Program and is partnering with Satinflower Nurseries to provide the MeadowMakers Program in Victoria.

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