A beloved native tree species is in trouble throughout the south Island.
Metchosin ecologist Andy MacKinnon is raising alarm bells for arbutus trees, as many are falling victim to a fungus called leaf blights. The leaf blights are a parasite to arbutuses, which have likely lived with the arbutus trees for a millennium, said MacKinnon.
“In a proper host-parasite relationship, the parasite doesn’t kill the host, it’s not a good strategy,” said MacKinnon. “But for whatever reason, these leaf blights are now having a rather severe effect on the arbutus trees. We are seeing their leaves and branches turn brown or black and then drop.”
MacKinnon said the parasites are affecting arbutus trees all over the area, and that a similar phenomena happened about five years ago, but not to this degree.
“It’s an unfortunate thing, because this is such a severe event, it is likely to kill a lot of the trees,” said MacKinnon. “Arbutus trees are a beloved tree to many people. They have magnificent, sweet-scented flowers and bright orange berries, and the magical, multi-coloured bark. They are a treasure.”
Arbutus is the only broad-leaf evergreen tree in Canada, and their populations here only reach the southeast regions of Vancouver Island, some Gulf Islands, as well as bits of the Lower Mainland.
“This area is the very northern end of the range for the arbutus. It is a wonderful and beautiful plant, with such a limited extent in Canada, so it is tragic to see all of these problems with it,” said MacKinnon. “They are a very different sort of tree for our forests in this area, which tend to be dominated by conifers such as Douglas fir and red cedars.”
Through his studies, MacKinnon attributes the issue to climate change, as the hotter, dryer, extended summers could be leaving arbutus trees in a weakened state, unable to ward off the fungus.
“The summer droughts are longer and more severe than in historical record, and this has put strain on arbutus trees. Some are in deep soils but many root in shallow soil over bedrock, in my observation these are the ones that are most severely affected,” said MacKinnon.
“There are leaf blights every single year, and most years, the trees sustain a little damage and carry on, so the question is why isn’t that happening this year? My interpretation is that we are dealing with some really stressed arbutus trees.”
Arbutus provide nectar flowers for a number of insect species, and the trees’ berries are an important food source for a variety of birds and other animals.
MacKinnon added that if you have an arbutus tree in your yard, offering it a little extra water and attention may help it gain some strength against parasites.
“I am interested and concerned about the fate of our native plants and fungi here,” said MacKinnon. “This is a good reminder that climate change isn’t something that’s going to happen. It’s been happening for a while, and has some important effects. It is a reminder that at some time or other, our governments will have to look seriously at the issue of dealing with climate change. There are bigger forces at play here.”
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