Environmental Problems, Their Causes, and Sustainability 1

How Are Human Activities Affecting theSulfur Cycle? Overloading NatureWe add sulfur dioxide to the atmosphere by burningcoal and oil, refining oil, and producing some metalsfrom ores.We add sulfur dioxide to the atmosphere in threeways. First, we burn sulfur-containing coal and oil toproduce electric power. Second, we refine sulfurcontainingpetroleum to make gasoline, heating oil,and other useful products. Third, we convert sulfurcontainingmetallic mineral ores into free metals suchas copper, lead, and zinc.Private owner 1Critical nesting sitelocationsUSDA Forest ServiceUSDAForest ServicePrivate owner 2Topography4-8 HOW DO ECOLOGISTS LEARNABOUT ECOSYSTEMS?What Is Field Research? Muddy BootsEcologyEcologists go into ecosystems and hang out in treetopsto learn what organisms live there and how theyinteract.Field research involves going into nature and observingand measuring the structure of ecosystems and whathappens in them. Most of what we know about thestructure and functioning of ecosystems described inthis chapter has come from such research.Ecologists trek through forests, deserts, and grasslandsand wade or boat through wetlands, lakes, andstreams collecting and observing species. Sometimesthey carry out controlled experiments by isolating andchanging a variable in part of an area and comparingthe results with nearby unchanged areas.Tropical ecologists erect tall construction cranesinto the canopies of tropical forests to identify and observethe rich diversity of species living or feeding inthese treetop habitats.Increasingly, ecologists are using new technologiesto collect field data. These include remote sensingfrom aircraft and satellites and geographic informationsystems (GISs), in which information gathered frombroad geographic regions is stored in spatial databases(Figure 4-35). Then computers and GIS software cananalyze and manipulate the data and combine themwith ground and other data. These efforts can producecomputerized maps of forest cover, water resources,air pollution emissions, coastal changes, relationshipsbetween cancers and sources of pollution, and changesin global sea temperatures.Most satellite sensors use either reflected light orreflected infrared radiation to gather data. However,some new satellites have radar sensors that measurethe reflection of microwave energy from the earth.WetlandLakeForestGrasslandHabitat typeReal worldFigure 4-35 Geographic information systems (GISs) providethe computer technology for organizing, storing, and analyzingcomplex data collected over broad geographic areas. GISsenable scientists to overlay many layers of data (such as soils,topography, distribution of endangered populations, and landprotection status).These microwaves can “see” in the dark and penetratesmoke, clouds, haze, and water. This method is alsobeing used to map the topography of the ocean floorand provide information about ocean currents andupward flows of nutrients from the ocean bottom (upwellings)that sustain fisheries.How Are Ecosystems Studied in theLaboratory? Life under GlassEcologists use aquarium tanks, greenhouses, andcontrolled indoor and outdoor chambers to studyecosystems.During the past 50 years, ecologists have increasinglysupplemented field research by using laboratory researchto set up, observe, and make measurements ofmodel ecosystems and populations under laboratoryconditions. Such simplified systems have been set upin containers such as culture tubes, bottles, aquariumtanks, and greenhouses and in indoor and outdoor84 CHAPTER 4 Ecosystems: What Are They and How Do They Work?