The Desmondium intortum grows in Ethiopia and has promising anti-parasitic properties (Copyright: Forest and Kim Star, 2004)

Why invasive plants are the 'second biggest threat to biodiversity' after habitat loss

Carrie Madren

23rd March,2011

As experts gather in London for a major conference addressing the often overlooked threat of invasive species to biodiversity, Carrie Madren gets a briefing from those on the frontline in the battle against 'pest plants'

We can eat oranges from South Africa, buy electronics made in China and can fly from the US to Europe in a matter of hours. As trade and travel have skyrocketed around the world, so too has our ability to bring exotic and foreign things back with us.

For centuries, horticulturists, plant lovers, ecologists, landscapers and others have imported plants for exotic aesthetic appeal, or usefulness in righting a degraded landscape.' As trade increased and travellers had the capacity to bring more things with them, it [the trade in invasive species] has proliferated,' says Lori Williams, executive director of the U.S. National Invasive Species Council.

Enthusiastic flora introductions have brought a raft of unintended consequences with them: at first a new plant succeeds but then adapts too well to its surroundings and spreads out of control. Some of these plants flourish so much in new territories that they became threats to native species’ very survival.

As well as intentional introductions, pest plants also travel 'undercover' - hitchhiker seeds and plants arrive in crates or crevices and sneak past border controls. Seeds get stuck in tyre or shoe treads or creep in as soft packing material....

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