Stem the Tide of Habitat Loss with Native Plants
By Irene Shonle:
At first blush, it may not seem like the choices you make on the plants you put in your garden make that much difference on a grand scale. You just pick what appeals to you (that you hope will grow in your yard) and plant it. Over the years, as I have evolved as a gardener, I’ve come to realize that there is much more to think about.
We can all make a difference with our gardens by helping restore some of the habitat that is being lost to development. Every day we hear news of pollinators and birds in decline, mostly due to habitat loss. Monarch butterflies and honey bees are known to be struggling, but populations of native bees and bird species that were thought to be wide-spread and stable are declining as well. The good news is that we as individuals are not powerless in this situation; adding native plants, even to existing gardens, can help turn that tide, especially if many people get on board.
With so much attention focused on the plight of non-native honey bees, the decline of native bees is often overlooked. These native pollinators are critical to support many native plants and are often important in pollinating crop plants as well. Gordon Frankie, a professor at the University of California at Berkeley, has shown that native plants are four times more likely to attract native bees than non-native plants. Planting a diversity (in bloom time, flower size, flower shape and species) of native plants will help support many native bees. Look at your property on a weekly basis during the growing season to make sure you have something in bloom. The pollinators have to eat every day, so plan for a sequence of blooms. For a fact sheet on low-water native perennials for pollinators, go here: https://conps.org/wp-content/uploads/2015/05/Low-Water-Native-Plants-for-Pollinators-brochure-6-8-15.pdf.
Native plants support butterflies in ways that traditional butterfly plantings – butterfly bush, zinnia, lantana, cosmos, and lilacs – cannot. These garden plants may well draw in adult butterflies, but they don’t support future generations. Butterflies have specialized requirements for rearing their caterpillars; they need the plants they have evolved with and can metabolize. Some butterfly species have narrowly specific hosts while others can use a broader range of plants, but natives are generally preferred. The females use chemical sensors on their legs to find the right plant that will support the growth of their caterpillars; if they can’t find the needed host plant(s), they won’t lay eggs and populations will decrease. The decline of the monarchs is largely due to the loss of the host milkweeds they depend on.
To support a range of these flying beauties, plant a variety of native plants across many families (sunflower, parsley, milkweed, willow, etc.). If there are specific butterflies you want to attract, you can look up native plant hosts by entering your zip code into this still-evolving website: http://www.nwf.org/NativePlantFinder.
The link between native plants and birds is more complicated. Many articles about bird gardening in the popular press suggest providing plants that have seeds, nuts, or fruit, but they include mostly non-native species (bachelor’s buttons, honeysuckle, Pyracantha, Russian olive, etc.). The field work of Dr. Doug Tallamy, University of Delaware professor and author of Bringing Nature Home, has shown that these non-native species do not support a crucial part of the bird life cycle – raising chicks. 98% of all bird species require insects (usually caterpillars or other soft-bodied insects) to fledge chicks, even when the adult birds eat seeds or fruits.
By careful observation, Tallamy discovered that chickadees require an astonishing 6,000 to 9,000 caterpillars/soft bodied insects just to raise one clutch! A large percentage of the insect herbivore species in any given ecosystem are specialists. They can only eat the few plant lineages that share the chemical defenses to which they have adapted, so it stands to reason that native plants do a better job of providing familiar food. Further studies by Tallamy and his lab demonstrated that properties rich in native plants supported significantly more caterpillars and caterpillar species and significantly greater bird abundance, diversity, species richness, biomass, and breeding pairs of native species. In this light, the way native plants support birds becomes clear.
Part of gardening for habitat is learning to accept some damage from caterpillars and other insects. The aesthetic of the perfect lawn and garden probably needs to be loosened a little in favor of supporting biodiversity. Instead of focusing on the holes in our plants, we can revel in the life we see in our gardens, and know that we’re doing something important to help so many other species.
Irene Shonle is the director of CSU Extension in Gilpin County. A long-time gardener with a passion for native plants, she teaches regularly around the state.