Appendix B Appendix C Appendix D Appendix E Appendix F BOX 3. Sorting out fact from fiction, however, is frequently problematic. Fortunately, credible information is available for some important phenomena. These global-scale indicators of change provide a credible platform for discussing environmental challenges. Examples include the conversion of wetlands and forests to urban and industrial areas or of grasslands to pastures and agricultural fields.
Humanity currently utilizes over half the available surface freshwater of the planet.
Demands for clean water are expected to rise as the human population grows exponentially. Human actions have doubled the amount of nitrogen fixed annually since the beginning of the century. This rearrangement of the biota of the planet is occurring at vastly greater rates due to human activities. Birds are one taxon for which reliable information about extinctions exists. For lesser-known taxa, credible estimates suggest that rates of species extinctions are approximately 100 to 1000 times those before humanity's dominance of Earth.