chapter 5

© 2011 Pearson Education, Inc.

Chapter 5Environmental Systems and Ecosystem Ecology


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


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


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• Negative and positive feedback loops do not mean bad and good

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


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


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


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

- 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 system of interest

It is hard to fully understand systems; they connect to other systems and do not have sharp boundaries


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


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

- Interactions and feedback loops


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


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

• Productivity = rate at which ecosystems generate biomass


Net primary productivity of various ecosystemsHigh 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


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


Eutrophication• The process of nutrient over enrichment, blooms of algae,

increased production of organic matter, and ecosystem degradation


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


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


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


Nutrients circulate through ecosystems

• 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

Nutrients can limit productivity

• Nutrients = elements and compounds required for survival that are consume by organisms

• Nitrogen and phosphorus are important for plant and algal growth


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 sponge-

like 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

evaporates


The hydrologic cycle water cycle


One Method of Water Use

Another Method of Water Use

VS.


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


The carbon cycle


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


The nitrogen cycle


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


• 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 low-nitrogen soils

• Changed estuaries and coastal ecosystems and fisheries

Humans affect the nitrogen cycle


Humans put nitrogen into the environment

Fully half of nitrogen entering the environment is of human originFarm Crisis of the 1980's


The phosphorus cycle


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 aquatic system, Do not buy detergents that contain phosphate


• Landscape ecology = studies how landscape structure affects the abundance, distribution, and interaction of organisms

- Helpful for sustainable regional development

Landscape ecology

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

- Habitat corridors that link patches protect biodiversity


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

- New data refine and increase the model’s accuracy


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

chapter 5

Technology

systems output

information systems

natural systems

river systems

partsenvironmental systems

systems work

earths environmental

environmental entities