Ninety percent of all insects are specialized, meaning they share an evolutionary history with native plants and rely on them to survive. Since animals directly or indirectly depend on plants for their food, the diversity of animals in a particular habitat is very closely linked to the diversity of plants in the habitat.
Tallamy, Douglas. Bringing Nature Home. Portland: Timber Press, 2007.
When certifying a site, we look for areas of one’s yard or outdoor space where the majority (50% or more) of plants in naturescaped areas are native to our specific ecoregion and 3 or more canopy layers are present throughout those naturescaped areas (as recommended in your site report). For the purposes of our program, we use the Portland Plant List (PPL) to determine whether a plant is native to our ecoregion, which is generally called the lower Willamette Valley (map). Our Naturescaping with Backyard Habitat video (4 minutes) and presentation (4 1/2 minutes) and Naturescaping with Natives Plants handout provide additional context.