Why invasive species are a problem.

What are invasive species, and why are they a problem? An undisturbed ecosystem will have an assortment of biotic factors - organisms - which are endemic to that environment. They have developed and evolved over time and found a natural balance with each other. Predator and prey relationships keep animals in balance and plants have developed into a climax community based upon abiotic factors such as soil, light, and moisture. Everything is in harmony. Then along comes an invasive species such as broom, or even worse, gorse.

Have a look at the image above. It is a photograph I took while visiting the south island in New Zealand. All that yellow you see on the hilltops are gorse, a relative of the broom plant. Introduced from England a mature plant can produce some 12,000 seeds annually. These get distributed widely about and produce whole new generations. Preferring drier, rocky soil, the plants are perfectly at home and quickly overgrow native vegetation. Nothing eats gorse and the plant outcompetes other species and takes over. The natural balance established over millennia gets overturned; vegetation that first-order consumers depended on is now scarce. Without food, those species either die out or are forced to forage elsewhere. Predators feeding on those herbivores now go hungry; their populations plummet due to starvation or emigration. The once productive community is left barren of life except for the invasive species which now controls it totally.

This may sound like hyperbole but the truth is it is happening all over the world. The best defense against invasives is education and action. The problem often comes from ignorance or apathy; it is terrible the toll that a single plant can have. Milfoil, knapweed, loosestrife - the list is long. In sewing these seeds of destruction we are cultivating our own doom. Unfortunately, the damage has already been done to so many areas. There is hope though as people are getting the message. Community and government agencies are attempting to remady the presence of these problem plants through the use of herbicides or burning. You can do your part by not adding to the problem and being aware.

Thanks for reading.     Ericspix     Eric Svendsen

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