Environmental Problems, Their Causes, and Sustainability 1

and other insect-eating birds feed on hordes of flies,mosquitoes, and caterpillars.What Are Temperate Rain Forests? DrippingGreen Giants and MossesCoastal areas support huge cone-bearing evergreentrees such as redwoods and Douglas fir in a cool andmoist environment.Coastal coniferous forests or temperate rain forests arefound in scattered coastal temperate areas with amplerainfall or moisture from dense ocean fogs. Densestands of large conifers such as Sitka spruce, Douglasfir, and redwoods dominate undisturbed areas of thesebiomes along the coast of North America, from Canadato northern California.Most of the trees are evergreen because the abundanceof water means that they have no need to shedtheir leaves. Tree trunks and the ground are frequentlycovered with mosses and ferns in this cool and moistenvironment. As in tropical rain forests, little lightreaches the forest floor.The ocean moderates the temperature so wintersare mild and summers are cool. The trees in thesemoist forests depend on frequent rains and moisturefrom summer fog that rolls in off the Pacific.Figure 6-33 lists major human impacts on theworld’s forests. What direct and indirect impacts doesyour lifestyle have on forest biomes?Natural Capital DegradationForestsClearing and degradation of tropicalforests for agriculture, livestockgrazing, and timber harvestingClearing of temperate deciduousforests in Europe, Asia, and NorthAmerica for timber, agriculture, andurban developmentClearing of evergreen coniferousforests in North America, Finland,Sweden, Canada, Siberia, and RussiaConversion of diverse forests to lessbiodiverse tree plantationsDamage to soils from off-road vehiclesFigure 6-33 Natural capital degradation: major humanimpacts on the world’s forests.6-7 MOUNTAIN BIOMESWhy Are Mountains Ecologically Important?High-Altitude Biodiversity SanctuariesMountains are high-elevation forested islands of biodiversityand often have snow-covered peaks that reflectsolar radiation and gradually release water tolower-elevation streams and ecosystems.Some of the world’s most spectacular and importantenvironments are mountains, which make up almost afourth of the world’s land surface. Mountains areplaces where dramatic changes in altitude, climate,soil, and vegetation take place over a very short distance(Figure 6-18, left).Because of the steep slopes, mountain soils are especiallyprone to erosion when the vegetation holdingthem in place is removed by natural disturbances(such as landslides and avalanches) or human activities(such as timber cutting and agriculture). Manyfreestanding mountains are islands of biodiversity surroundedby a sea of lower-elevation landscapes transformedby human activities.Mountains play important ecological roles. Theycontain the majority of the world’s forests, which arehabitats for much of the world’s terrestrial biodiversity.They often are habitats for endemic species foundnowhere else on earth, and they serve as sanctuariesfor animal species driven from lowland areas.They also help regulate the earth’s climate whentheir snow- and ice-covered tops reflect solar radiationback into space. Mountains affect sea levels as a resultof decreases or increases in glacial ice—most of whichis locked up in Antarctica (the most mountainous of allcontinents). Finally, mountains play a critical role inthe hydrologic cycle by gradually releasing meltingice, snow, and water stored in the soils and vegetationof mountainsides to small streams.Despite their ecological, economic, and culturalimportance, the fate of mountain ecosystems has notbeen a high priority of governments or many environmentalorganizations. Mountain ecosystems arecoming under increasing pressure from several humanactivities (Figure 6-34, p. 126). What direct or indirectimpacts does your lifestyle have on mountainbiomes?In this chapter we examined the connectionsamong weather, climate, and the distribution of theearth’s terrestrial biomes. Three general ecologicallessons emerge from this study. First, different climatesoccur as a result of currents of air and water flowingover an unevenly heated planet spinning on a tiltedaxis. Second, different climates result in different communitiesof organisms, or biomes. Third, everything isconnected.http://biology.brookscole.com/miller14125