Although gardeners are accustomed to coping with variable weather conditions, in some parts of the country warmer-than-usual summers and winters with skimpy snow cover have gone from the exception to the expected.
Fundamentally, today’s climate is much different from that of 10 or 15 years ago. According to Daniel McKenney of Natural Resources Canada, Canadian Forest Service, research shows “there is strong evidence of a pending and profound change in global climate as a result of human activities. Recent estimates predict an increase in global mean temperature of 2.4 to 6.4 degrees Celsius by the end of the century.”
And climate isn’t changing equally across the country, either. “The extreme minimum temperatures of the East Coast are not currently [increasing] as much as those on the West Coast,” says McKenney, adding that melting glaciers probably help keep the east relatively cool.
Mapping climate change
McKenney and colleagues are gathering useful information in Going Beyond the Zones, an interactive online project started in 2001 to develop climatic profiles for individual trees, shrubs and herbaceous perennials. By documenting the possible range of each species, gardeners, commercial growers and the forestry industry have accumulated details for as many as 5,000 species and generated maps for 2,500. The data show the impact climate change has on where plants will grow (for more information about the ongoing project, visit planthardiness.gc.ca).
Certainly, temperature changes on a global scale could be devastating, but milder winters don’t always spell bad news for gardeners. “The biggest change is in plant survival,” says Deborah Sirman, co-owner of Greenland Garden Centre in Sherwood Park, Alberta. “For example, most euonymus are hardy to Zone 5, so we used to mulch in order for them to withstand winter here in Zone 3; but now many varieties are fine on their own.”