Newscientist.com brings us an article on the alien invaders laying waste to the Galapagos Islands. In fact, there are two sets of invaders: pests such as rats and goats, and tourists who will soon be coming by the cruise-ship-load. As you know, because each island was so isolated, the species living on each could evolve in peace to best suit the environment. And by comparing what he found on each island, Darwin evenutally formulated his famous theory on the origin of species.
At any rate, this isolation and ultra-optimization to the environment left the native flora and fauna susceptible to invaders, such as the previously-mentioned rats and goats. Being from a more competitive environment, the invaders quickly outcompeted and overran the natives. As mentioned in the article, environmentalists have taken steps to eradicate the invaders. For example, a pesticide specially formulated to be toxic only to rats will be sprayed across one island. Once the invaders have been exterminated, they be replaced with compatible species from the other islands.
My thought is that this is just a foreshadowing of what will happen when we finally go to the stars. My concern is which role will we be playing? Will we be the Pinta tortoise, driven to extinction by alien goats? Will we be the tourists, obliviously spreading destruction in our wake? Will we be the rats, nibbling our way across the cosmos? And if so, will somebody out there be spraying us with Human-Be-Gone?