Invasive Species

One of the biggest threats to natural environments worldwide is the prevalence and spread of invasive species. From the microscopic to the continent encompassing humanity has managed to put spread plants and animals to places where they out-compete, directly predate or otherwise harm the native flora and fauna.

In the UK American Grey Squirrels Sciurus carolinensis have driven back native Red Squirrels Sciurus vulgaris to the fringes by spreading a disease that greys are impervious to, but reds find fatal. Some species, such as Ruddy Ducks Oxyura jamaicensis, introduced to the UK, spread as far as Spain where they could interbreed with the closely related White-headed Duck Oxyura leucocephala, so have been irradicated. American Mink Neogale vison, released by well-meaning but ignorant animal welfare protestors, still survive in great numbers, despite effort, and have driven Water Voles Arvicola amphibius to the edge. Himalayan Balsam Impatiens glandulifera clogs British waterways and is impossible to eradicate.

In Australia grasses like Gamba Grass Andropogon gayanus imported from tropical Africa to feed cattle, now swamps many native grasses and is a massive wild-fire risk. Cane Toads Rhinella marina poison native Herons when they ingest them. In New Zealand mustelids and possums, feral cats, pigs and goats have driven many native species to extinction. Everywhere humanities ‘pets’ such as domestic cats ravage local wildlife and accidentally introduced rats drive many species such as ground nesting birds to the brink.

The jury is still out on species such as the Asian Ring-necked Parakeets Psittacula krameri (featured) which escaped captivity in the UK, other European cities and in the USA, may out-compete natives for nest holes or food.

Some people and governments throw up their hands and declare that the tide cannot be turned, while others plod along doing what they can and yet others make groundbreaking stands. New Zealand aims to eliminate all introduced mammals over the next twenty years. South Georgia was declared rodent free after a ten-year battle. Elsewhere off-shore islands, or ‘defendable’ inland areas have been successfully cleared of invasive reptiles, mammals and plants.

However, Florida’s wetlands in the US have more Burmese Pythons Python bivittatus than Burma and more Green Iguanas Iguana iguana than all of the Caribbean!

We can all do our bit by helping to weed out invasive plants and take part in programmes to push back invading species and protect native wildlife.