Chapter 5


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Chapter 5

  1. 1. Chapter 5 Environmental Systems and Ecosystem Ecology © 2011 Pearson Education, Inc.
  2. 2. OBJECTIVES Chapter 5: Environmental Systems and Ecosystem Ecology •Describe the nature of environmental systems and how systems work •Define ecosystems and evaluate how living and nonliving entities interact in ecosystem-level ecology •Outline the fundamentals of landscape ecology, GIS, and ecological modeling •Assess ecosystem services and how they benefit our lives •Compare and contrast how water, carbon, phosphorus, and nitrogen cycles interact with the environment •Explain how human impact is affecting biogeochemical cycles © 2011 Pearson Education, Inc.
  3. 3. Central Case: The Gulf of Mexico’s “Dead Zone” • The Gulf of Mexico brings in a billion pounds/year of shrimp, fish, and shellfish • Gulf “dead zone” = a region of water so depleted of oxygen - That marine organisms are killed or driven away • Hypoxia = low concentrations of dissolved oxygen in water - From fertilizer, fossil fuel emissions, runoff, sewage © 2011 Pearson Education, Inc.
  4. 4. Earth’s environmental systems • Our planet’s environment consists of complex networks of interlinked systems - Matter and molecules - Organisms, populations, interacting species - Nonliving entities (rocks, air, water, etc.) • A systems approaches assesses questions holistically - Helping address complex, multifaceted issues - But systems can show behavior that is hard to understand and predict Systems show several defining properties • • • System = a network of relationships among parts, elements, or components They interact with and influence one another - They exchange energy, matter, or information Systems receive inputs of energy, matter, or information - They process these inputs and produce outputs • Feedback loop = a circular process in which a system’s output serves as input to that same system © 2011 Pearson do not • Negative and positive feedback loopsEducation, Inc.mean bad and good
  5. 5. Negative feedback loop • Negative feedback loop = output from a system moving in one direction acts as input - That moves the system in the other direction • Input and output neutralize one another - Stabilizes the system - Example: predator – prey interactions • Most systems in nature © 2011 Pearson Education, Inc.
  6. 6. Positive feedback loop • Positive feedback loop = instead of stabilizing a system, it drives it further toward one extreme or another - Exponential growth in human population, erosion, melting sea ice • Rare in nature - But is common in natural systems altered by humans © 2011 Pearson Education, Inc.
  7. 7. Systems are active • Dynamic equilibrium = system processes move in opposing directions - Balancing their effects • Homeostasis = a system maintains constant (stable) internal conditions • Emergent properties = system characteristics are not evident in the components alone It is hard to fully understand systems; they connect to other systems and do not have sharp boundaries - The whole is more than the sum of the parts Environmental systems interact • Environmental entities: complex, interacting systems • For example, river systems consist of hundreds of smaller tributary subsystems - Impacted by farms, cities, fields, etc. • Solving environmental problems means considering all appropriate components in the © 2011 Pearson Education, Inc. system of interest
  8. 8. Systems are perceived in various ways • Categorizing environmental systems helps make Earth’s dazzling complexity comprehensible • For example, the earth consists of structural spheres - Lithosphere = rock and sediment - Atmosphere = the air - Hydrosphere = liquid, solid or vapor water - Biosphere = all the planet’s living organisms and the abiotic portions of the environment • Boundaries overlap, so the systems interact © 2011 Pearson Education, Inc.
  9. 9. Ecosystems • Ecosystem = all organisms and nonliving entities that occur and interact in a particular area at the same time - Includes abiotic and biotic components - Energy flows and matter cycles among these components • Biological entities are highly intertwined with chemical and physical entities © 2011 - Interactions and feedback loops Pearson Education, Inc.
  10. 10. Ecosystems integrate spatially • Ecosystems vary greatly in size • The term “ecosystem” is most often applied to self-contained systems of moderate geographic extent • Adjacent ecosystems may share components and interact • Ecotones = transitional zones between two ecosystems in which elements of different ecosystems mix Conservation biology • Conservation biologists = study the loss, protection, and restoration of biodiversity • Habitat fragmentation = breaking habitat into small, isolated patches due to human impact - Corridors of habitat can link patches © 2011 Pearson Education, Inc.
  11. 11. Energy is converted to biomass • Primary production = conversion of solar energy to chemical energy by autotrophs • Gross primary production (GPP) = assimilation of energy by autotrophs • Net primary production (NPP) = energy remaining after respiration, and is used to generate biomass - Available for heterotrophs • Secondary production = biomass generated by heterotrophs © 2011 Pearson Education, Inc.
  12. 12. Net primary productivity of various ecosystems High net primary productivity = ecosystems whose plants rapidly convert solar energy to biomass NPP variation causes global geographic patterns NPP increases with temperature and precipitation on land, and with light and nutrients in aquatic ecosystems © 2011 Pearson Education, Inc.
  13. 13. The Gulf of Mexico from a systems perspective • Nutrients from fertilizers spread on Midwestern farms and urban lawns enter the Mississippi River • Fertilizer use has increased, which causes…. • Phytoplankton to grow, then… • Bacteria eat dead phytoplankton and wastes and deplete oxygen, causing… • Fish and other aquatic organisms to suffocate . . . • Which causes loss of fishing grounds . . . • Which causes economic impact to Louisiana Fishermen © 2011 Pearson Education, Inc.
  14. 14. Eutrophication • The process of nutrient over enrichment, blooms of algae, increased production of organic matter, and ecosystem degradation © 2011 Pearson Education, Inc.
  15. 15. Nutrient runoff is devastating aquatic systems • Dead zones of water result from nutrient pollution from farms, cities, and industry • Pollution and human impact have devastated fisheries and altered aquatic ecosystems • Scientists are investigating innovative and economical ways to reduce nutrient runoff Phytoplankton blooms off the Louisiana coast © 2011 Pearson Education, Inc.
  16. 16. Worldwide marine dead zones dead zone • Over 400 dead zones occur globally - Most are off the coasts of Europe and the U.S. - Mostly due to farm, city and industrial pollution - Some are seasonal, others are permanent • Fisheries and ecosystems are devastated - Causing over $2 billion/year in lost harvests © 2011 Pearson Education, Inc.
  17. 17. Solutions to the dead zone • • The Harmful Algal Bloom and Hypoxia Research and Control Act (1998) - Called for an assessment of hypoxia in the dead zone Solutions outlined included: - Reduce nitrogen fertilizer use in Midwestern farms - Apply fertilizer at times which minimize runoff - Use alternative crops and manage manure better - Restore wetlands and create artificial ones - Improve sewage treatment technologies - Evaluate these approaches Decreasing pollution • Scientists, farmers and policymakers are encouraged to - Decrease fertilizer use, while safeguarding agriculture • Offering insurance and incentives • Using new farming methods • Planting cover crops • Maintaining wetlands • There have been some successes - Despite a lack of funding © 2011 Pearson Education, Inc.
  18. 18. Nutrients circulate through ecosystems • • Nutrients = elements and compounds required for survival that are consume by organisms Nitrogen and phosphorus are important for plant and algal growth Nutrients can limit productivity • Physical matter is circulated continually in an ecosystem • Nutrient (biogeochemical) cycle = the movement of nutrients through ecosystems - Atmosphere, hydrosphere, lithosphere, and biosphere • Pools (reservoirs) = where nutrients reside for varying amounts of time • Flux = movement of nutrients among pools, which change over time and are influenced by human activities © 2011 Pearson Education, Inc.
  19. 19. The hydrologic cycle • • • • • • • • Water is essential for biochemical reactions and involved in nearly every environmental system Hydrologic cycle = summarizes how liquid, gaseous and solid water flows through the environment Evaporation = water moves from aquatic and land systems into the atmosphere Transpiration = release of water vapor by plants Precipitation, runoff, and surface water = water returns to Earth as rain or snow and flows into streams, oceans, etc. Groundwater Aquifers = underground reservoirs of spongelike regions of rock and soil that hold… - Groundwater = water found underground beneath layers of soil Water table = the upper limit of groundwater in an aquifer - Water may be ancient (thousands of years old) Groundwater becomes exposed to the air where the water table reaches the surface - Exposed water runs off to the ocean or © 2011 Pearson Education, Inc. evaporates
  20. 20. The hydrologic cycle water cycle © 2011 Pearson Education, Inc.
  21. 21. One Method of Water Use VS. Another Method of Water Use © 2011 Pearson Education, Inc.
  22. 22. Human impacts on hydrologic cycle • Damming rivers increases evaporation and infiltration • Altering the surface and vegetation increases runoff and erosion • Spreading water on agricultural fields depletes rivers, lakes and streams • Removing forests and vegetation reduces transpiration and lowers water tables • Emitting pollutants changes the nature of precipitation • The most threatening impact is overdrawing groundwater for drinking, irrigation, and industrial use © 2011 Pearson Education, Inc.
  23. 23. The carbon cycle © 2011 Pearson Education, Inc.
  24. 24. • • • • • • • • • • The carbon cycle Carbon is found in carbohydrates, fats, proteins, bones Carbon cycle = describes the routes that carbon atoms take through the environment Photosynthesis moves carbon from the air to organisms Respiration returns carbon to the air and oceans Decomposition returns carbon to the sediment, the largest reservoir of carbon - Ultimately, it may be converted into fossil fuels The world’s oceans are the second largest reservoir of carbon Humans affect the carbon cycle Burning fossil fuels moves carbon from the ground to the air Cutting forests and burning fields moves carbon from organisms to the air Today’s atmospheric carbon dioxide reservoir is the largest in the past 650,000 years - The driving force behind climate change The missing carbon sink: 1-2 billion metric tons of carbon are unaccounted for - It may be the plants or soils of northern temperate and boreal forests - Carbon Cycle © 2011 Pearson Education, Inc.
  25. 25. The nitrogen cycle © 2011 Pearson Education, Inc.
  26. 26. The nitrogen cycle nitrogen cycle • Nitrogen comprises 78% of our atmosphere, and is contained in proteins, DNA and RNA • Nitrogen cycle = describes the routes that nitrogen atoms take through the environment - Nitrogen gas is inert and cannot be used by organisms • Nitrogen fixation = Nitrogen gas is combined (fixed) with hydrogen by nitrogen-fixing bacteria to become ammonium - Which can be used by plants • Nitrification = bacteria that convert ammonium ions first into nitrite ions then into nitrate ions - Plants can take up these ions - Animals obtain nitrogen by eating plants or other animals • Denitrifying bacteria = convert nitrates in soil or water to gaseous nitrogen, releasing it back into the atmosphere Pearson Education, Inc. © 2011
  27. 27. Humans affect the nitrogen cycle • Haber-Bosch process = synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia - Dramatically changed the nitrogen cycle - Humans are fixing as much nitrogen as nature does • Increased emissions of nitrogen-containing greenhouse gases • Calcium and potassium in soil washed out by fertilizers • Acidified water and soils • Moved more nitrogen into plants and terrestrial systems • Reduced biodiversity of plants adapted to lownitrogen soils • Changed estuaries and coastal ecosystems and fisheries © 2011 Pearson Education, Inc.
  28. 28. Humans put nitrogen into the environment Fully half of nitrogen entering the environment is of human origin Farm Crisis of the 1980's © 2011 Pearson Education, Inc.
  29. 29. The phosphorus cycle © 2011 Pearson Education, Inc.
  30. 30. The phosphorus cycle phosphorus cycle • Phosphorus (P) is a key component of cell membranes, DNA, RNA, ATP and ADP • Phosphorus cycle = describes the routes that phosphorus atoms take through the environment • Most phosphorus is within rocks - It is released by weathering with no significant atmospheric component • With naturally low environmental concentrations - Phosphorus is a limiting factor for plant growth Humans affect the phosphorus cycle • Mining rocks for fertilizer moves phosphorus from the soil to water systems • Wastewater discharge also releases phosphorus • Runoff containing phosphorus causes eutrophication of aquatic systems - Produces murkier waters, Alters the structure and function of © 2011 Pearson Education, Inc. aquatic system, Do not buy detergents that contain phosphate
  31. 31. Landscape ecology • Landscape ecology = studies how landscape structure affects the abundance, distribution, and interaction of organisms - Helpful for sustainable regional development • Metapopulations and conservation biology Metapopulation = a network of subpopulations - Most members stay within patches - Some individuals may move among patches or mate with those of other patches - Individuals in small, isolated patches risk extinction • Conservation biologists = study the loss, protection, and restoration of biodiversity • Human development fragments habitat - Creating small, isolated patches © 2011 Pearson Education, Inc. - Habitat corridors that link patches protect biodiversity
  32. 32. Remote sensing applies landscape ecology • Remote sensing allows scientists to take a landscape perspective • Geographic information system (GIS) = computer software used in landscape ecology research - Analyzes how elements of a landscape are arranged - Helps in planning and land-use decisions Modeling helps us understand systems • A model = a simplified representation of a complex natural process - Helps us understand the process and make predictions • Ecological modeling = constructs and tests models - To explain and predict how ecological systems work • Researchers gather data and form a hypothesis about relationships - Models predict how the system will behave © the model’s accuracy - New data refine and increase 2011 Pearson Education, Inc.
  33. 33. • Ecosystems provide vital services – ROBERT COSTANZA Human society depends on healthy, functioning ecosystems - They provide goods and services we need to survive • Ecosystem services = provided by the planet’s systems - Soil formation, water and air purification, pollination - Breakdown of some pollutants and waste - Quality of life issues (inspiration, spiritual renewal) - Nutrient cycling © 2011 Pearson Education, Inc.