US-based sustainable sneaker brand Allbirds sources one of its core materials from South Africa. The Allbirds running shoes launched last week, Tree Runners, features an upper made from eucalyptus from South African farms.

“This fibre is one of the most sustainable materials on the planet,” said Joey Zwillinger, co-founder of the company, speaking to the New Yorker.

The eucalyptus is farmed locally, using no irrigation. Allbirds dissolves the wood pulp in a non-toxic bath to convert it into tufts of fibre called Tencel.

“Our tree fibre—TENCEL™ Lyocell—is sourced from South African farms that minimise fertiliser and rely on rainfall, not irrigation,” the company says on its website. “Compared to traditional materials like cotton, it uses 95% less water and cuts our carbon footprint in half.”

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Allbirds is Forest Stewardship Council  (FSC) certified, the body responsible for responsible forest management. “FSC ensures that we’re not only protecting forests, but the people, wildlife, and ecosystems that depend on them.”

Other parts of the Tree Runner is also sustainable: the laces are made from recycled plastic bottles, the insole is made from caster beans, and the eyelets are based on plant starch.

According to the South African National Biodiversity Institute (SANBI), eucalyptus is a diverse genus of flowering trees and shrubs belonging to the myrtle family Myrtaceae. It is not indigenous to South Africa.

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“Outside their natural ranges, eucalypts are both lauded for their beneficial economic impact and criticised for being ‘water-guzzling’ invasive aliens, leading to controversy over their total impact,” says SANBI.