Chapter 19 Endangered Species 469 Copyright Goodheart-Willcox Co., Inc. Habitat Fragmentation Habitat fragmentation is the division of a large, continuous habitat into smaller, disconnected pieces. These actions separate feeding grounds, affect migration patterns, and reduce the living space for many animals. Species often become isolated in each area and may experience genetic mutations over time that enable survival. However, if the species cannot adapt, the isolation may cause its decline or extinction. For example, dams constructed to establish reservoirs or generate power make it diffi cult for migrating fi sh to travel to their spawning areas. This type of restriction leads to population decline and may result in the loss of genetic diversity within a species, which may eventu- ally cause its extinction. In some cases, the fragmentation presents additional hazards for ani- mals as they must cross busy roads and contend with fast-moving vehi- cles. In Australia, for example, as urbanization and deforestation reduce the koala’s habitat, the koalas are forced to cross roads to reach separated parts of their habitat. According to the Department of Environment and Heritage Protection in Australia, about 300 koalas are killed on the roads in Queensland each year. Invasive Species The introduction of an invasive species commonly causes habitat destruc- tion and degradation. Invasive species typically have few predators, develop rapidly with a short reproduction cycle, and quickly acclimate to the new envi- ronment. Native species typically cannot defend themselves or compete with aggressive invasive species. Many North American trees, for example, have succumbed to attack from the invasive, Asian longhorn beetle. See Figure 19-5. Many native species are also susceptible to predation and to disease introduced through the invasive species. What immediate effect does deforestation have on the water cycle? Thinking Critically Would a South American piranha survive in the Great Lakes? Would it pose a threat to the ecosystem? Explain your answer. Thinking Critically TTstudio/Shutterstock.com Figure 19-5. Invasive species in the United States include the Asian longhorned beetle (Anoplophora glabripennis), cogon grass (Imperata cylindrical), and the European starling (Sturnus vulgaris). What effect has each of these species had on the environment and our native species? feathercollector/Shutterstock.com tamu/Shutterstock.com