The Toronto Valley rules are based on the idea that as a species grows over generations, it develops characteristics specific to its location, so that a tree grown from a seed collected in Toronto is more likely to flower when native pollinators are active than a seed of the same species grown at a lower latitude.
Foresters say there’s another good reason to try to preserve as many native trees as possible: For some indigenous peoples and indigenous peoples who have deep ties to certain tree species, phasing them out could be the latest in a long history of cultural and physical land dispossession.
For example, in the Pacific Northwest, Western Red Cedar (one word because it is not a real cedar) is central to Native American cultural practices for many local tribes. Some groups refer to themselves as “Cedar Tree PeopleUsing logs For canoesbasketry, medicines, etc.
But the tree no longer thrives in many areas of Portland, Oregon, due to drying soils, said Jen Cairo, the city’s urban forestry manager. The city has faced deadly heat waves and drought in recent years. As a result, the city of Portland has recommended that the species be planted only in optimal conditions on its list of approved street trees. “We’re not going to eradicate the tree, but we are careful about where we plant it,” she said.
A similar strategy is being adopted in Sydney, where Port Jackson fig trees are struggling but a closely related Moreton Bay fig is thriving. Urban forestry manager Karen Sweeney said the city was considering irrigated parkland as habitat for native species dying elsewhere in the city. “We often say we’re happy to do it where we can find a place,” she said.
When introducing new tree species to supplement urban canopies, we need to ensure that the newcomers do not spread invasively, dominating new habitats and damaging native species.
There are many examples to avoid. Norway maple, native to Europe and Western Asia, Escaped the boundaries of North American citiesIt creates excessive shade and crowds out understory plants, making it an invasive species that displaces native species. In the Valley In Toronto. A Robinia pseudoacacia tree native to China. Accumulates chemicals in soil They damage nearby plants, forming dense patches of grass and crowding out native species. In some parts of the U.S., including Indiana, residents I was urged to raise Native to Australia, the highly flammable eucalyptus has spread its roots around the world. The risk of wildfires also increases.
Urban tree experts don’t believe invasive species cause much disruption to native wildlife, and if done right, they can bring diversity to cities dominated by invasive species. One type of tree It can reduce the problem caused by waves of pests and diseasesA mix of plant species could act as a buffer to prevent tree-to-tree infections among the same species. Esperon Rodrigues, an ecologist at the University of Western Sydney, says it’s possible for a new plant species to replace a plant used by an animal that relies on one kind of plant for survival, but such cases are the exception rather than the rule.
