Why Reforest London wants the city to stop planting invasive trees

Reforest London is calling on the city to stop planting invasive species that areimpacting local ecosystems.

The non-profitorganization iswarningthatinvasive trees and shrubscouldgrowand kill native plants in London. The intruders oftenaggressivelyuseupwater,nutrients and sunlight that wouldotherwisebe available to nativespecies.

DeanSheppard, executive director of Reforest London, said the city needs stricter guidelines surrounding planting invasive trees.

"There's a disconnect between what (the city) is planting and its invasive species management," he said.

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Cityarboristsplant about 5,000 trees every year to keep up with the removal of aging ordying trees and a number of invasive species are among a list of species approved by the city.

A city list of approved street trees suggested that about 20 per cent are deemed as invasive.

Jill-AnneSpence, the city's urban forestry manager, saidinvasive plants have abetterchance ofsurvivingin a harsh urban setting such as London.

"We're planting them in rare incidences where no other or very limited types of trees will grow because of harsh environmental conditions," she said.

Spencesaid the city avoids planting invasive species near conservation areas such as Westminster Ponds. The cityplants invasive species along boulevards where theyare better able to deal with thelimited soil spaceandharsh chemical sprays.

But Sheppardsaid planting invasive trees and shrubs can affect thewider ecosystem.

"If you want to have healthy woodland, you need a diverse mix of species and animals that have evolved here together for a long time," he said. "An invasive species disrupts that it totally crashes that."

In 2014, a city strategy emphasized the management of natural areas to proactively tackle invasive species and enhance native species.

List of city approved invasive trees:

• Hedge Maple
• Amur Maple
• Norway Maple
• Sycamore Maple
• Tatarian Maple
• Horsechestnut
• European Alder
• European Hornbeam
• AmurMaackia
• Crab Apple
• Callery Pear
• European Mountain Ash