Chapter 7. Climate and Biodiversity.pdf

Miller_17e_Ch07.pptx (Download above the PowerPoint file for this chapter. Below is a summary/ outline of the chapter)...

Miller_17e_Ch07.pptx (Download above the PowerPoint file for this chapter. Below is a summary/ outline of the chapter) CHAPTER 7 CLIMATE AND ECOSYSTEM BIODIVERSITY Chapter Outline The following outline organizes activities (including any existing discussion questions in PowerPoints or other supplements) and assessments by chapter (and therefore by topic), so that you can see how all the content relates to the topics covered in the text. 7. Climate A. The earth has many different climates. 1. Weather is a set of physical conditions such as temperature, precipitation, humidity, wind, speed, cloud cover, and other factors in a given area for short periods of time. 2. Climate is an area’s general pattern of atmospheric conditions over periods ranging from 30 to thousands of years. 3. Earth’s current major climate zones and ocean currents are key components of the earth’s natural capital (Figure 7.2). 4. Climate varies in different parts of the earth primarily because of several factors: a. Greenhouse gases (see Science Focus 7.1) b. Solar energy-driven cyclical movement of air in convection cells and the earth’s rotation on its axis (Hadley cells, Fig. 7.3, 7.4) c. Uneven heating of the earth’s surface by the sun—hotter at the equator due to the sun’s rays hitting directly over a smaller area, compared to a larger area near the poles d. Global air circulation and ocean currents distribute heat and precipitation unevenly between the tropics and other parts of the world (Fig. 7.2, 7.4, 7.5) 5. Prevailing winds blowing over the oceans produce mass movements of surface water called ocean currents. Major ocean currents help to redistribute heat from the sun, influencing climate and vegetation, especially near coastal areas. 6. El Niño–Southern Oscillation (ENSO) is an example of the interaction between the ocean and atmosphere. a. Large-scale weather phenomenon occurring every few years when prevailing winds in the tropical Pacific Ocean weaken and change direction. b. Above-average warming of Pacific waters alters the weather in 2/3 of the earth for 1–2 years, leading to milder winters in some areas. B. Science Focus 7.1: Greenhouse Gases and Climate 1. Greenhouse gases in the lower atmosphere absorb and release heat, which warms the atmosphere, influencing the earth’s average temperatures and its climates. The major greenhouse gases are: a. Water vapor (H2O) b. Carbon dioxide (CO2) c. Methane (CH4) d. Nitrous oxide (N2O) 2. The natural greenhouse effect is a warming of the lower atmosphere and the earth’s surface. Some of the energy that the earth’s surface absorbs from the sun is radiated into the atmosphere as heat. Greenhouse gases absorbed some of this heat which warms the lower atmosphere, causing the greenhouse effect. 3. Without this natural warming effect, the earth would have an average temperature of near −18°C (0°F). 4. Human activities are releasing large amounts of greenhouse gases, intensifying the natural greenhouse effect. C. The earth’s surface features affect local climates. 1. Heat is absorbed and released more slowly by water than by land, creating land and sea breezes. 2. Mountains interrupt the flow of prevailing surface winds and the movement of storms. 3. High mountains create the rain shadow effect (Figure 7.7) 4. Cities with bricks, asphalt, and traffic create distinct microclimates, notably, heat islands. 7. Terrestrial Ecosystems and Human Activity A. Climate helps to determine where organisms can live. 1. Average annual precipitation and temperature lead to the formation of tropical (hot), temperate (moderate), and polar (cold) deserts, grasslands, and forests. 2. Climate and vegetation vary with latitude and elevation. 3. Biomes are large regions, each characterized by certain types of climate and dominant plant life. 4. Biomes are not uniform. They consist of a mosaic of patches, each with somewhat different biological communities but with similarities typical of the biome. 5. Transitions between two different biomes or ecosystems are called ecotones, displaying the edge effect, a tendency towards greater species diversity and higher density of organisms than either of the individual ecosystems. B. There are three major types of desert. 1. Deserts have low annual precipitation often scattered unevenly throughout the year. The sun warms the ground during the day and evaporates water; heat is quickly lost at night. 2. Tropical deserts (e.g., the Sahara) are hot and dry most of the year, with few plants. 3. Temperate deserts have high daytime temperatures in summer and low in winter; generally more precipitation than tropical deserts. Sparse vegetation comprises mostly cacti and other succulents. 4. Cold deserts (e.g., the Gobi desert in Mongolia) have sparse vegetation, cold summers and precipitation is low. 5. Desert soils take from decades to centuries to recover from disturbances such as off-road vehicle travel because deserts have slow plant growth, low species diversity, slow nutrient cycling, and very little water. C. Science Focus 7.2: Staying Alive in the Desert 1. Adaptations for survival in the desert have two themes: beat the heat and every drop of water counts. 2. In plants, leaves are designed to minimize water loss and root systems to maximize water collection. Many plants have spines to avoid being eaten by herbivores seeking the water they hold. 3. Most desert animals are small. Some are nocturnal and hiding in cool burrows during the day and others are dormant during periods of extreme heat or drought. Some larger animals can drink massive quantities of water when it is available and store it in their fat for use as needed. Some get their water from their food. 4. Insects and reptiles have thick outer coverings to minimize water loss through evaporation. Many spiders and insects get their water from dew or from the food they eat. D. There are three major types of grasslands. 1. Grasslands occur mostly in the interiors of continents in areas too moist for deserts and too dry for forests. 2. Grasslands are not taken over by shrubs and trees because of seasonal droughts, grazing by large herbivores, and occasional fires. 3. The three main types of grassland: a. Tropical, for example, savanna Savanna contains widely scattered clumps of trees and is usually warm year-round with alternating dry and wet seasons. Home to grazing and browsing animals b. Temperate, for example, short-grass and tall-grass prairies Temperate grassland winters can be very cold, while summers are hot and dry. Annual precipitation is fairly sparse and falls unevenly through the year. Aboveground parts die each year and decompose, building fertile topsoil held by a thick network of intertwined roots. Many temperate grasslands have been converted for growing crops and grazing cattle. c. Cold, for example, cold grasslands or arctic tundra Cold grasslands, or arctic tundra, are bitterly cold, treeless plains. Permafrost forms when frozen underground soil exists for more than two consecutive years, which melts to form shallow aquatic habitats during the brief (7- to 8-week) summer. Tundra usually has nutrient-poor soil and is vulnerable to disruption. E. Science Focus 7.3: Revisiting the Savanna: Elephants as a Keystone Species 1. Ecologists view elephants as a keystone species. 2. Elephants eat woody shrubs and young trees that help keep the savanna from being overgrown and grasses from drying out. 3. Elephants also dig for water during periods of droughts, creating large watering holes that are used by other animals. 4. Without elephants, the food web in the African savanna would collapse. 5. Elephants are vulnerable to extinction. a. In 1979, there were an estimated 1.3 million wild elephants and today there is an estimated 415,000 that remain in the wild. b. The sharp decline is due to killing them for ivory. c. Another major threat is the loss/fragmentation of their habitat, which has led to some farmers killing elephants. F. Forests are lands dominated by trees. 1. The three main types of forest: a. Tropical forests are found near the equator with a constant warm and wet climate, which is ideal for a wide variety of plants and animals. They are dominated by broadleaf evergreen plants that keep most of their leaves year-round. There is little vegetation on the forest floor because the dense tree-top canopy blocks lightest from reaching the ground. Very high net primary productivity and an incredible high level of biological diversity Cover about 7% of the earth’s land surface but are estimated to contain at least 50% of the earth’s known terrestrial plant and animal species Species live in five vegetation layers, from top to bottom: emergent, canopy, under story, shrub, and ground layer (see Figure 7.14). High nutrient turnover in soil results in thin, vulnerable topsoil b. Temperate forests are of two main types: Temperate deciduous forests, the most common, have warm summers, cold winters, and abundant precipitation. Broadleaf deciduous trees dominate, which drop leaves in the fall. Decomposition is slower than in tropical forests, resulting in greater nutrient storage. Coastal coniferous forests, or temperate rainforests, have ample rainfall and moisture from ocean fogs. Coniferous evergreen trees dominate, such as the giant sequoia. c. Cold, northern coniferous forests, are also called boreal forests or taigas. Limited sunlight and frozen soil moisture in the winter Comprised by a few species of evergreen trees; decomposing conifer needles makes soil acidic and prevents most plants from growing G. Individuals Matter: Sereivathana Tuy, Elephant Protector 1. Since 1970, the rain forest cover in Cambodia has dropped from 70% to 3% due to population growth, rapid development, illegal logging, and warfare. 2. Severe forest loss has forced elephants to search for food and water on farmlands, leading poor farmers to kill elephants to protect their food supply. 3. Since 1995, Tuy has had two goals: a. Double the population of Cambodia’s endangered elephants by 2030. b. Show poor farmers that protecting elephants and other forms of wildlife will help them escape poverty.  4. Tuy helped farmers set up a nighttime watch for elephants, taught them how to scare elephants away, and encouraged them to grow plants that elephants shun. 5. Since 2005, no elephants have been killed in human conflict. H. Mountains play important ecological roles. 1. Mountains are steep or high-elevation lands where dramatic changes in altitude, slope, climate, soil, and vegetation take place over a very short distance. 2. About 1 billion people (13% of the world’s population) live in mountain ranges or their foothills, and 2 billion people (25% of the world’s population) depend on mountain systems for all or some of their water. 3. Many mountains are islands of biodiversity surrounded by a sea of lower-elevation landscapes transformed by human activities. 4. Important ecological roles include: a. Contain a large portion of the world’s trees b. Habitats for endemic specie c. Sanctuaries for species that can migrate and survive in higher altitudes, some of which are driven from lowlands by human activities or a warming climate 5. Connections: Mountains and Climate a. Mountains help regulate the earth’s climate, with the ice-covered tops reflecting the sun and the exposed rocks absorbing the heat, and cause rain shadows. b. Atmospheric warming is causing many mountain glaciers to melt. The exposed rocks are darker than ice so absorb more solar energy. This warms the atmosphere above them, which melts more ice and warms the atmosphere more in an escalating cycle of change. 6. Mountains play a critical role in the hydrologic cycle by serving as major storehouses of water. I. Humans have disturbed much of the earth’s land. 7. About 60% of the world’s major terrestrial ecosystems are being degraded or used unsustainably, as the human ecological footprint gets bigger and spreads across the globe (see Figure 7.15). 7. Marine Ecosystems and Human Activity A. Most of the earth is covered with water. 1. About 71% of the earth’s surface is covered with salty ocean water. 2. One global ocean, divided into four large areas by geographers a. Atlantic Ocean b. Pacific Ocean (The largest ocean, which contains more than half of the earth’s water and covers one-third of the earth’s surface) c. Arctic Ocean d. Indian Ocean 3. Aquatic life zones are the aquatic counterparts of biomes. 4. Distribution of aquatic organisms is determined largely by the water’s salinity—the amounts of various salts such as sodium chloride (NaCl) dissolved in a given volume of water. 5. Aquatic life zones are classified into two major types: a. Saltwater or marine life zones: oceans and their bays, estuaries, and other coastal systems b. Freshwater life zones: lakes, rivers, streams, and inland wetlands 6. Key factors determining the type and number of organisms at various depths include: a. Water temperature b. Dissolved oxygen content c. Availability of food d. Availability of light and nutrients required for photosynthesis B. Oceans provide vital ecological and economic services. 1. Enormous reservoirs of biodiversity with three major life zones, the coastal zone, open sea, and ocean bottom. 2. The coastal zone (See Figure 7.17) a. Warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the edge of the continental shelf b. Makes up less than 10% of the world’s ocean area while containing 90% of all marine species and is the site of most large commercial marine fisheries c. Estuaries and coastal wetlands are large aquatic ecosystems. Estuaries are where rivers meet the sea, forming partially enclosed bodies of water where seawater mixes with freshwater as well as nutrients and pollutants from streams and runoff from the land. Coastal wetlands are areas covered with water all or part of the year and include coastal marshes and mangrove forests. d. Sea grass beds and coral reefs are important shallow-water ecosystems. 3. Coastal aquatic systems provide vital ecological and economic services such as: a. Maintain water quality in tropical coastal zones by filtering toxic pollutants, excess plant nutrients, and sediments, and by absorbing other pollutants b. Provide food, habitats, and nursery sites for a variety of aquatic and terrestrial species c. Reduce storm damage and coastal erosion by absorbing waves and storing excess water produced by storms and tsunamis C. Science Focus 7.4: Coral Reefs 1. Form in clear, warm coastal waters in tropical areas 2. Among the world’s oldest, most diverse, and most productive ecosystems. 3. Formed by massive colonies of polyps that build reefs by secreting a protective crust of limestone, resulting in an elaborate network of crevices, ledges, and holes 4. The mutually beneficial relationship between polyps and zooxanthellae is an example of mutualism, where the algae provide the polyps with food and oxygen. The polyps provide the algae with a well- protected home and nutrients. 5. Coral reefs provide important economic and ecosystem services: a. They act as natural barriers that protect 15% of the world’s coastline from flooding and erosion. b. They provide habitats, food, and spawning grounds for ¼ to 1/3 of the organisms that live in the ocean. c. They also produce about 1/10th of the global fish catch. 6. Coral reefs are vulnerable to damage because they grow slowly and disrupt easily. 7. Two major long-term threats to coral reefs are climate change and ocean acidification. a. Coral bleaching occurs when stresses such as increased temperature cause the symbiotic zooxanthellae to die. Without food, the coral polyps die, leaving behind a white skeleton of calcium carbonate. b. Ocean acidification makes it harder for marine organisms to build hard structures such as reefs. D. The open sea and the ocean floor host a variety of species. 1. The open sea occurs beyond the edge of the continental shelf and is divided into three vertical zones largely on the basis of the penetration of sunlight. a. The euphotic zone is the brightly lit upper zone, where drifting phytoplankton carry out about 40% of the world’s photosynthetic activity. b. The bathyal zone is the middle zone, which gets little sunlight and, therefore, does not contain photosynthesizing producers. c. The lowest zone, called the abyssal zone, is dark and very cold; it has little dissolved oxygen. Its inhabitants get their food from “marine snow,” showers of dead and decaying organisms that drift down from the upper levels. 2. Net primary productivity (NPP) is low, except in upwelling areas where currents bring up nutrients from the ocean bottom. The ocean’s large size makes it the biggest contributor to the earth’s overall NPP. E. Human activities are disrupting and degrading marine ecosystems. 1. Areas most affected are coastal marshes, shorelines, mangrove forests, and coral reefs 2. Major threats to marine systems from human activities are summarized in Figure 7.22. 3. The biggest threat to marine systems is climate change. a. Sea levels are rising due to thermal expansion and melting glaciers. b. Because oceans absorb much of the excess heat and CO2, they are warming and becoming more acidic. 7. Freshwater Ecosystems and Human Activity A. Water stands in some freshwater systems and flows in others. 1. Precipitation that does not sink into the ground or evaporate becomes surface water. a. Surface water becomes runoff when it flows into streams or lakes. b. A watershed, or drainage basin, is the land area that delivers runoff, sediment, and dissolved substances to a stream or lake. 2. Freshwater life zones include standing bodies of freshwater such as lakes, ponds, and inland wetlands, and flowing systems such as streams and rivers, all covering less than 2.5% of the earth’s surface. a. Lakes are large natural bodies of standing freshwater formed when precipitation, runoff, streams and rivers, and groundwater seepage fill depressions. Deep lakes consist of four zones: Littoral—where water meets land; plants support wildlife Limnetic—open water zone; too deep for plants; has free-floating organisms Profundal—deep zone below range of effective light penetration Benthic—lowest zone, contains sediments that provide nutrients for organisms living there b. Lakes are classified according to nutrient content and primary productivity. Oligotrophic (poorly nourished) lakes have a small supply of plant nutrients, causing them to look crystal clear. Eutrophic (well-nourished) lakes have a large supply of nutrients needed by producers, causing them to have high productivity and look murky brown or green. Cultural eutrophication occurs when human inputs of nutrients from the atmosphere and from nearby urban and agricultural areas accelerate eutrophication. B. Freshwater streams and rivers carry water from the mountains to the oceans. 1. In a watershed, water accumulates in small streams that join to form rivers. Collectively, they carry huge amounts of water from highlands to lakes and oceans. 2. The downward flow of surface water and groundwater from mountain highlands to the sea typically takes place in three aquatic life zones characterized by different environmental conditions: a. The source zone, made up of headwater streams in higher elevations b. The transition zone, with wider, lower-elevation streams c. The floodplain zone, where rivers empty into larger rivers or the ocean 3. Streams shape the land through which they pass, forming deep canyons over millions of years. 4. Streams carry sand, gravel, and soil and deposit them as sediments in lower-lying areas. 5. Deltas are areas at the mouth of a river built up by sediments and often contain estuaries and coastal marshes. They absorb and slow the velocity of floodwaters from coastal weather events and provide habitats for marine life. C. Freshwater inland wetlands are vital sponges. 1. Inland wetlands are lands covered with freshwater all or part of the time (excluding lakes, reservoirs, and streams) and located away from coastal areas. a. Marshes (dominated by grasses and reeds with few trees) b. Swamps (dominated by trees and shrubs) c. Prairie potholes (depressions carved out by ancient glaciers) d. Floodplains (receive excess water during heavy rains and floods) 2. Inland wetlands provide a number of free ecological and economic services, which include: a. Filtering and degrading toxic wastes and pollutants b. Reducing flooding and erosion by absorbing storm water and releasing it slowly, and by absorbing overflows from streams and lakes c. Maintaining stream flows during dry periods d. Helping to recharge groundwater aquifers  e. Helping to maintain biodiversity by providing habitats for a variety of species f. Supplying valuable products such as fishes and shellfish, blueberries, cranberries, and wild rice g. Providing recreation for birdwatchers, nature photographers, boaters, anglers, and waterfowl hunters D. Human activities are disrupting and degrading freshwater systems. 1. Dams and canals alter and destroy terrestrial and aquatic wildlife habitats along rivers and in their coastal deltas and estuaries by reducing water flow and increasing damage from coastal storms. 2. Flood control levees and dikes built along rivers disconnect the rivers from their floodplains, destroy aquatic habitats, and alter or reduce the functions of nearby wetlands. 3. Cities and farms add pollutants and excess plant nutrients to nearby streams, rivers, and lakes. This can cause explosions in the populations of algae and cyanobacteria, which deplete the lake’s dissolved oxygen. Fishes and other species may then die off, which causes a major loss in biodiversity. 4. Many inland wetlands have been drained or filled to grow crops or have been covered with concrete, asphalt, and buildings. 5. More than 50% of the inland wetlands in the continental U.S. have been lost, which has increased flood damage in the U.S. E. Individuals Matter: Alexandra Cousteau: Environmental Storyteller and National Geographic Explorer 1. Granddaughter of Captain Jacques-Yves Cousteau and the daughter of Philippe Cousteau, legendary underwater explorers who brought the wonders of the ocean to living rooms through their books and films 2. Alexandra’s work focuses on advocating the importance of conservation and sustainable management of water to preserve a healthy planet. 3. Utilizes tools such as social networking and mobile communication and imagines that one day we should be able to check water quality like we check the weather.