Native Plants are Key to Saving Birds, Pollinators, and Biodiversity

-Erin K O’Hara

There are many known benefits of biodiversity. More biodiverse ecosystems are more productive. They capture more energy from the sun through photosynthesis, and then feed more insects and animals through the increased plant biomass. Biodiversity also leads to greater sequestration of carbon, water filtration, and oxygen production. Additionally, diverse ecosystems prevent pest outbreaks, and deter invasive species. [i] When all the ecological niches are filled by competing organisms, there simply isn't space for invaders to colonize.  Biodiverse ecosystems are also much more stable than simple ones.  If one species is lost from the food web, the web will not collapse, as another species will step in to do the job. One of the easiest ways for gardeners to contribute to the food web and increase biodiversity in their landscapes is to plant native, as indigenous plants are critical components of a functioning ecosystem. Studies have shown that native plants support many times more insect biomass than alien species, including 4 times more insect herbivore biomass, and 3.2 times more species overall. [ii]

One of the most compelling reasons to promote native plants is that 90% of herbivorous insects are plant specialists, requiring one genus or just one species of plant that they co-evolved with to survive. It takes millions of years for most insects to adapt to the specific chemical deterrents that are present in a particular plant or group of plants. Essentially, if you take away the host plant you lose the insect species that has adapted to its unique chemical composition. Only 1% of the 4 million insect species are “pests.” The other 99% pollinate plants, turn dead plants and animals into compost, prey on insect herbivores, aerate the soil, and are a critical food source for birds and other creatures. 96% of terrestrial birds feed their young exclusively on insects and spiders, with Lepidoptera (butterflies and moth) larva making up the bulk. [iii] Take away the insects and you take away the birds, as it has been found that locally adapted plants support a whopping 35 times more Lepidoptera biomass! [iv] Amphibians, reptiles, and small mammals also largely depend on insects.

Focusing your gardening efforts on supporting pollinators, like native bees and butterflies, is a great place to start supporting biodiversity. This is because bees are responsible for the majority of pollination services needed by flowering plants, and birds depend on moth and butterfly larva to feed their young. Choosing a number of plants that have a variety of flower types and that bloom throughout the season is important for getting the maximum number of pollinators to stick around.  Butterflies and moths have a long proboscis and so reach isn't a problem for them. However, most of them do not hover to feed, so they need a place to land while they sip nectar. Many plants have evolved wide landing areas that accommodate this need, such as Echinacea spp, Rudbeckia spp, Goldenrods, and Liatris spp. There are over 4000 species of native bees. The small, short tongued bees, such as sweat bees, can only reach into shallow flower tubes. They favor plants like Culvers Root (Veronicastrum virginicum), Coreopsis spp, Asters, and the Mountain Mints (Pycnanthemum spp). Flowers with longer tubes, like the penstemons, columbine, Monarda spp, and Virginia Bluebells (Mertensia virginica) are favored by medium to large sized bees and bumblebees, whose tongue length usually corresponds to body size. Turtle Hill offers plant species adapted to suit butterflies and bees of all sizes. Please see our plant list for this years offerings. Be sure to take note of the bloom times in the plant description, so your garden offers beauty, color, and pollinator food throughout the growing season.

[i] Science 309:68-71. 2005. Food Web Ecology: Playing Jenga and Beyond. De Ruiter, P.C., V. Wolters, J.C. Moore, and K.O. Winemiller

[ii] Timber Press, Portland, OR. 2007. Bringing Nature Home. pp 59-60. Douglas W Tallamy.

 [iii] National Geographic Society. Washington, DC. 1999. Field Guide to the Birds of North America, 3rd edition. Dickinson, M.B.

[iv] Timber Press, Portland, OR. 2007. Bringing Nature Home. pp 59-60. Douglas W Tallamy.