Magazine article New Internationalist

An Alien Invasion

Magazine article New Internationalist

An Alien Invasion

Article excerpt

For over 2,000 years, humans have benefited from the introduction of new plant species - which add variety to our diets and provide colour and diversity. However, a small number of introduced plant species actually threaten native biological diversity.

Invasive plant species (such as Oxford Ragwort, pictured here) are a global problem. Some arrive accidentally: for example, in packing material on ships; others are planted deliberately as ornamental plants in gardens or crops. By taking the light, nutrients and space normally occupied by native plants, invasive species alter the environment. The absence of their natural predators, competitors and diseases means there is little to control their growth. Some species poison the surrounding soil so that other plants cannot grow there; others grow very quickly, preventing light from reaching slower-growing or shorter plants. By decreasing plant diversity, they can deprive animals of habitats. Aquatic plants, imported from overseas and sold for use in gardens ponds, have spread into wild areas and now threaten many sites across Britain. Once established, they smother native plants, clog waterways, worsen flooding and remove oxygen from the water, which can harm fish. …

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