Doug Tallamy, American
entomologist, ecologist and conservationist recommends that 70% of plants in a
garden should be native species to
provide a seasonal food source for larval caterpillars, which specific
bird species depend upon as they fledge their young. It’s
become a popular talking point over the last few years, especially on social
media. It’s a worthwhile goal, and I encourage anyone to follow this advice
should they wish to do so. He writes also on the importance of pollinating insects.
Much of the current concern about pollinators took off after a report from Germany showed a drastic reduction in insects there. This was picked up by the media and made for alarming headlines — dramatic events are more publishable. Yet unlike Europe where almost all land has been modified for human use, findings indicate that large-scale insect declines across North America remain an open question. There are few studies showing an overall decline, although this doesn’t mean there are not areas where this has occurred.
This raises questions for me about the situation in this area. Prior to a couple of hundred years ago, southern Ontario was heavily forested, then the forests were felled to make way for farmland and much of the natural landscape was lost. Urban growth followed, absorbing swaths of that farmland, then in the decades following World War II, all manner of pesticides became available. They were heavily used in agriculture, by municipalities, and by homeowners.
This was a time when green lawns ruled and to ensure they stayed that way, they were sprayed heavily with weedkillers — remember the tanker trucks that roamed neighbourhoods leaving a chemical smell in the air? Thankfully, that ended in 2008 with the Ontario pesticide act.
Prior to about thirty years ago, other than grass, homes might have had a small vegetable plot out back with room for a clothesline. In the front yard, most had only what was termed a foundation planting out front, three or four evergreens and limited selection of flowering plants. There were far fewer sources for plants compared to now when big box and grocery stores have become garden centres. Filling the front and back yard with rare and unusual plants would have been seen as radical. This began to change largely due to the Communities in Bloom program starting in 1998, which encouraged front yard plantings, and over the last twenty years interest in growing flowering plants has surged.
Growing vegetables, too, has become hugely popular. However, backyards are still largely a play area for kids and pets, although many trees and shrubs have been added where none grew before. People build gardens for many reasons, and in an urban environment it isn’t easy to recreate a natural ecosystem where plants and insects have developed a complex web of interrelationships, yet those who opted to plant flower gardens with a wide range of plants have done much to support pollinators. Non-native plants might not cater to all species of insects, but they can provide nectar rich flowers for generalist feeders, and native birds and insects will happily feed on both native and non-native plants. It’s the specialist feeders that are most in need of specific plants that support them, like the monarch butterfly that relies on milkweed.
Planting any kind of garden is a positive thing when one considers what is being done to the planet, especially so as climate change, pesticide use, and loss of greenbelt continue to threaten pollinating insects on a much bigger scale than a simple garden that has long provided habitat where non existed before. So yes, do avoid using invasive, exotic plants, and certainly add more native species to attract pollinators, even 70%, but don’t be afraid to grow what you love, providing it causes no harm to the environment — know your plants.
It is worth noting that in the US, where the movement is strongest, pesticide use by home gardeners is still permitted. Eighty-five types of pesticide outlawed in other countries are still allowed there.