The forest understory vegetation community is a key ecosystem component of Haida Gwaii forests. Understory plants provide food for native fauna (bears, birds etc.), structure for nesting habitat (eg. songbirds, auklets), and medicines for Haida use (among others). In Gwaii Haanas, 3 sites are monitored every 10 years to detect any abnormalities in the known successional sequence of dominance for 14 key plants. Any shift away from normal succession indicates a stressor is having an effect on the understory. Stressor examples include: deer, squirrel, insects and climate (and many others).