Arbutus menziesii also known as Pacific Madrone Tree is a striking work of nature. It is the only broad-leafed evergreen tree in Canada and thrives in open, rocky outcrops near the ocean and occasionally in deeper soils in forest openings. In undisturbed habitat, Arbutus is extremely hardy, withstanding drought, extreme wind, poor nutrients, and wildfires. Arbutus trees quite often live to be hundreds of years old! However, with the intensification of anthropogenic land use and development Arbutus has suffered. Across its range on Vancouver Island, Arbutus is in decline.

Arbutus plays a significant, though indirect, role in local food security. The sweet, honey-scented flowers support native pollinator populations which have also been in decline in recent years. Native sources of pollen, such as Arbutus flowers and the wildflowers pictured here, can help support the native insects who pollinate BC crops and orchards. Without pollination, growing food would not be possible. Arbutus is also an important food source for Rufous hummingbirds who drink Arbutus nectar and for robins, waxwings, thrushes, and woodpeckers who eat the Arbutus berries.

Andy MacKinnon, a professional forester and biologist, offered some insight into Arbutus decline, (see video here) describing how the age-old relationship between Arbutus and fungal leaf blights have been impacted by climate change. While the organisms involved have not changed, Arbutus is less hardy and more susceptible to defoliation due to eroding soils, dry summers, and stress from human disturbances.

The black spots which appear on the leaves from the blight eventually spread, and leaves and branches wither. The blight may cause partial or complete defoliation, meaning that the tree may lose all its leaves. Partial defoliation every few years because of blight is not abnormal, however, Arbutus trees weakened by climate and stress are more likely to be defoliated by the blight entirely, or two years consecutively which may kill them.

According to Andy, “This is not an introduced species that is wreaking havoc with the Arbutus population, these are native species killing trees they’ve probably lived with for thousands of years.” Andy also discusses the fact that because this is a natural interaction which has been aggravated by a changing climate, chemical fungicides will not be a solution. To kill off the leaf blight with an aggressive and toxic treatment would not address the fact that the necessary environment for Arbutus is disappearing. It is also important to remember that while chemical pesticides and fungicides may offer what appears to be a faster and more direct solution to blight, the impact of that chemical use on an ecosystem can be incredibly destructive. This is particularly true when in the vicinity of water systems; as most Arbutus trees thrive in coastal systems any chemical treatments can contaminate the ocean.