Zebra mussels have invaded the great lakes causing all kinds of economic and ecological problems.
[link|http://www.glsc.usgs.gov/main.php?content=research_invasive_zebramussel&title=Invasive%20Invertebrates0&menu=research_invasive_invertebrates|http://www.glsc.usgs...ive_invertebrates]
One species perseveres at the expense of others. Life always expands to new territories. That's the thing about living systems- they're never in equilibrium. Everything is moving and changing. In a sense, everything is always on the edge of collapse. But life always seems to find a way- it just may not be the life we want.