19 Apr The Alien Invasion
Human beings are found in more places and in more diverse habitats than any other creature on earth. From the deserts of Africa to the jungles of the Asian tropics, from the frozen Arctic tundra’s to the high mountains of Nepal, people are everywhere.
As homo-sapiens moved from one area to another in search of a better life or merely out of curiosity. Often, by mistake or by design they brought new species into new areas. This may have been plants like clover for cattle feed, fruit trees, flowering plants for gardens or trees for timber and firewood as well as animals like rats and cockroaches.
What these people didn’t realise was that these new species didn’t belong to those areas and when you put something where it doesn’t belong, trouble is sure to follow.
In their natural habitats, plants, animals and fungi have developed a homeostasis or balance. For example there are enough herbivores to ensure certain plants don’t grow out of control and then there are enough carnivores to make sure that the herbivorous population doesn’t explode and upset the balance.
However when an alien species is introduced the natural checks and balances that keep its population limited are not in place. This is when we see populations get out of control. This further upsets the natural balance and we can see entire ecosystems dwindle and vanish.
With plants there can be some unexpected consequences of alien invasion. An interesting example is our Cape Vynbos. This extremely diverse ecosystem is tied into a burn cycle. Every few years natural bush fires would sweep through the areas. The fires would clear large swathes of older vegetation and make these area available for new plants to grow. The local vegetation burns at a low temperature and the plant seeds have evolved tough shells that crack open when exposed to this specific heat range. Unfortunately, alien vegetation burns much hotter. This means that instead of freeing the viable seed and starting a new generation of plants, the new fires simple burn everything to a crisp leaving lands that cannot rehabilitate themselves as the seed stock has been destroyed.
Alien plants also often use more water than their indigenous cousins and they choke up rivers and streams putting further pressure on local ecosystems and this can have major consequences downstream.
Aliens also compete for space, light and nutrients in the battle for survival.