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Figure 11.2Invasive organisms create problems by dominating their local ecosystems. (a) Kudzu, introduced into North America to stop highway erosion, rapidly overgrows other plants. (b) Purple loosestrife, introduced from Europe as a garden flower, has invaded many North American wetlands. (c) Zebra mussels aggressively colonize and overwhelm ordinary mussels. In 2002, the U.S. Fish and Wildlife Service estimated that $5 billion was spent by electric utility companies just to unclog water intake pipes blocked by zebra mussels.