In the United States, the need to protect plant and animal species has become a highly controversial and sharply political issue since the passage of the Enered Species Act in 1973．The act, designed to protect species' living areas, and policies that preserve land and forests compete with economic interests．In the 1990's, for example, the woodcutters in the Western United States were challenged legally in their attempt to cut trees for timber in the Cascade Mountains, The challenge was mounted to protect the enered spotted owl (猫头鹰), whose remaining population occupies these forests and requires the intact, ancient forest for survival．The problematic situation set the interests of environmentalists against those of corporations and of individuals who stood to lose jobs．After months of debate and legal battles, the fate of the woodcutters and the owls was still undecided in mid- 1992.
Similar tensions exist between the developed and the developing nations．Many people in industrialized nations, for example, believe that developing nations in tropical regions should do more to protect their rain forests and other natural areas．But the developing countries may be impoverished (使穷困), with populations growing so rapidly that using the land is a means to temporarily avoid worsening poverty and starvation.
Many of the changes to Earth that concern scientists have the potential to rob the planet of its biological richness．The destruction of Earth's ozone layer (臭氧层), for example, could contribute to the general process of impoverishment by allowing ultraviolet rays to harm plants and animals．And global warming could wipe out species unable to quickly adapt to control human population, stabilize the composition of the atmosphere, and preserve intact Earth's complex web of life.
Why does the author say that the protection of enered species is a highly controversial issue?