The Biosphere and Human Effects
Chapter 18
18.3 Types of Land Ecosystems
 Different climates support different types of plant
life, which support different types of animals
 Biome
• Type of ecosystem that can be characterized by
its climate and dominant vegetation
Deserts
 Low rainfall produces deserts at latitudes around
30° north and south, where dry air descends
 Desert
• Biome where little rain falls, humidity is low, and
the main plants store water in their tissues or tap
into water sources deep underground
Desert
Grasslands
 Grasslands form at midlatitudes in the interior of
continents between deserts and temperate
forests
 Grasslands
• Biome where grasses and other low-growing
plants are adapted to warm summers, cold
winters, periodic fires, and grazing animals
• Example: shortgrass and tallgrass prairies
Chaparral
 Dry shrublands (chaparral) are found in South
Africa, California, and Mediterranean regions
 Chaparral
• Biome where cool, wet winters and hot, dry
summers support shrubs adapted to periodic fires
Grasslands and Chaparral
Grassland, shrublands,
and woodlands
Fig. 18-5c, p. 365
Tropical Rain Forests
 At the equator, high rainfall and temperature
support tropical rain forests with broadleaf trees
that remain green year-round
 Tropical rain forest
• Species-rich tropical biome in which continual
warmth and rainfall allows dominant broadleaf
trees to grow all year
Tropical Rain Forest
Deciduous Broadleaf Forests
 Deciduous broadleaf trees are adapted to
regions that cannot sustain year-round growth
 Deciduous tree
• A tree that drops all its leaves annually just before
a season that does not favor growth
 Temperate deciduous forest
• Biome dominated by trees that drop all their
leaves and go dormant during a cold winter
Deciduous Broadleaf Forest
Coniferous Forests
 Conifer forests dominate high latitudes in the
Northern Hemisphere and other regions where
drought, poor soil, or periodic fires prevent
broadleaf trees from taking hold
 Taiga (boreal forest)
• Extensive northern biome dominated by conifers
• A cold, dry season alternates with a cool, rainy
season
Coniferous Forest: Siberian Taiga
Tundra
 Tundra forms at high latitudes and high altitudes
 Arctic tundra
• Youngest, most northerly biome, dominated by
low plants adapted to a short growing season and
a layer of permanently frozen soil (permafrost)
 Alpine tundra
• High-altitude biome dominated by low plants
Arctic Tundra
Animation: Major biomes
Animation: Environmental gradient
18.4 Types of Aquatic Ecosystems
 Composition of aquatic communities is
influenced by gradients of sunlight penetration,
water temperature, salinity, dissolved gases,
rate of water movement, and depth
Freshwater Ecosystems
 A lake is a standing body of water
• Light decreases with depth; different communities
live at different depths and distances from shore
 Streams and rivers are flowing water ecosystems
• Physical characteristics that vary along its length
influence the types of organisms that live in it
• Fast-flowing cooler water holds more oxygen than
warmer, slower-moving water
Marine Ecosystems
 Estuary
• A semi-enclosed area where nutrient-rich water
from a river mixes with seawater
• Highly productive ecosystem
 Seashores
• Rocky shores have grazing food chains based on
algae; sandy shores have detrital food chains
Marine Ecosystems
 Benthic province
• The ocean’s rocks and sediments
 Pelagic province
• The ocean’s open waters
• In upper waters, photosynthetic organisms form
the basis of grazing food chains
• Deeper communities subsist on materials that
drift down from above
Marine Ecosystems
 Coral reefs
• Formation composed of secretions of coral
polyps, found in tropical, sunlit seas
• Main producers are photosynthetic protists that
live inside the coral’s tissues
 Coral bleaching
• Stress response in which a coral expels the
photosynthetic protists in its issues
Coral Reef and Bleaching
water of the open ocean
air at ocean
surface
water over
continental shelf
continental
shelf
Pelagic
Province
0
200
1,000
2,000
4,000
11,000
depth (meters)
deep-sea
trenches
Fig. 18-10a, p. 369
Animation: Oceanic zones
Marine Ecosystems
 Seamount
• An undersea mountain
 Hydrothermal vent
• Place where hot, mineral-rich water streams out
from an underwater opening in the Earth’s crust
• Producers are prokaryotes that strip energy from
minerals
Seamounts and Hydrothermal Vents
Comparing Aquatic Ecosystems
 In well-lit upper waters, photosynthetic
producers are the base for grazing food chains
 Detritus drifting down from above sustains most
deep-water communities in lakes and oceans
 Hydrothermal vent communities on the ocean
floor are sustained by energy that prokaryotes
harvest from minerals
Animation: Lake zonation
Animation: Lake turnover
Animation: Rocky intertidal zones
Animation: Three types of reefs
Animation: Hydrothermal vent
community
Animation: Coastal upwelling
18.5 Human Effects on the Biosphere
 The increasing size of the human population and
its increasing industrialization have far-reaching
effects on the biosphere
 Effects range from extinction of individual
species to global climate change
Increasing Species Extinctions
 Humans are increasing the rate of species
extinctions by degrading, destroying, and
fragmenting natural habitats, by overharvesting
species, and by introducing exotic species
Increasing Species Extinctions
 Endangered species
• Faces extinction in all or part of its range
 Threatened species
• Likely to become endangered in the near future
 Endemic species
• Evolved in one place and is found nowhere else
Living or Extinct?
 Ivory-billed woodpecker
Threatened Species
 Habitat destruction threatens the eastern prairie
fringed orchid – aquifer depletion and pollution
endanger Texas blind salamanders
Some Threatened Species
The Global Impact of Human Activities
 Human activities threaten entire ecosystems
•
•
•
•
•
•
•
Desertification
Deforestation
Air pollution and acid rain
Water pollution
Trash in aquatic ecosystems
Air pollution and the ozone hole
Greenhouse gases and global warming
Desertification
 Poor agricultural practices turn grasslands or
woodlands into deserts
• US Great Plains (the Great Dustbowl)
• Sahara Desert
 Desertification
• Conversion of grassland or woodlands to
desertlike conditions
Desertification
 Dust from the Sahara over the Atlantic Ocean
Deforestation
 Human activities strip woodlands of trees
•
•
•
•
Flooding
Landslides
Increases atmospheric CO2
Decreases atmospheric oxygen
 Deforestation
• Removal of all trees from a large tract of land
Deforestation
 Clearing tropical forests in Brazil
Pollution
 Human activities generate pollutants that kill
animals and damage ecosystems
 Pollutant
• Natural or man-made substance released into the
environment in greater than natural amounts, and
that damages the health of organisms
Acid Rain
 Acid rain
• Rainfall contaminated by acidic pollutants
• Burns trees, kills fish, leaches nutrients from soil
 Caused by pollutants that combine with water
vapor in the atmosphere to form acids
• Sulfuric acid from sulfur dioxides from coalburning power plants and factories
• Nitric acid from nitrogen oxides from vehicles and
power plants that burn gas and oil
Acid Rain
Other Sources of Water Pollution
 Pollution from point sources may be identified;
dealing with pollution from nonpoint sources is
more difficult
• Industrial chemicals and heavy metals
• Oil from vehicles
• Runoff of fertilizers, pesticides, herbicides, and
animal wastes
• Sewage and excreted prescription drugs
• Sediments
Some Results of Water Pollution
 Bioaccumulation
• Concentration of toxins such as mercury as they
move up through the food chain
 Eutrophication
• Nutrient enrichment by sewage and fertilizers,
resulting in toxic algal blooms or oxygen depletion
 Turbidity
• Clouding of water by sediment runoff, blocking
sunlight and choking animals
The Trouble With Trash
 Human activities generate plastics and other
trash that kill animals and damage ecosystems
• Chemicals from buried trash contaminate
groundwater
• Wastes dumped or washed into the ocean
damage marine ecosystems
• Plastics can persist more than 100 years
The Trouble With Trash
 More than 300 pieces of plastic fed to an
albatross chick by its parents
Air Quality
 Pollution from airborne particles damages
respiratory systems of humans and animals
• Burning of fossil fuels and industrial processes
 Some pollutants have global effects
• CFCs cause thinning of the ozone layer
• Rising levels of greenhouse gases contribute to
climate change
Air Quality
The Ozone Hole
 Ozone is a pollutant near the ground, but
depletion of the ozone layer is a global threat
caused by the use of CFCs
• Global agreement to phase out CFC use
 Ozone layer
• Atmospheric layer with a high concentration of
ozone that prevents much ultraviolet radiation
from reaching Earth’s surface
Ozone and CFCs
Animation: How CFCs destroy ozone
Global Climate Change
 Climate change caused by rising concentrations
of greenhouse gases is another global threat
• Results in extremes in rainfall patterns and
drought, increased hurricane intensity
 Global climate change
• Global warming and other changes in the current
climate and weather patterns
Evidence of a Warming World
Causes of Climate Change
 Earth’s climate normally cycles from icy to hot
•
•
•
•
Earth’s orbit changes in a 100,000 year cycle
Earth’s tilt varies in a 40,000 year cycle
Periodic changes in solar output
Occasional effects of volcanic eruptions
 Recent warming is due to increase in
greenhouse gases due to human activities
• 2007 Intergovernmental Panel on Climate Change
Climate Change and Greenhouse Gases
Fueling Global Climate Change
Effects of Climate Change
 Increasing temperature causes sea level rise
• Increased coastal erosion and flooding
• Salt water contamination of freshwater aquifers
 Temperature effects on biological systems
•
•
•
•
Earlier spring flowering in plants
Shifts in animal migration and breeding seasons
Ecosystems shift to higher latitudes or altitudes
Stressed aquatic systems, such as corals
Animation: Global crises by region and
habitat
Animation: Habitat loss and
fragmentation
Animation: Humans affect biodiversity
Animation: Formation of photochemical
smog
Animation: Chernobyl fallout
Animation: Stream pollution
Video: ABC News: Air pollution in China
Video: ABC News: Beach pollution
Video: ABC News: China computer waste
Video: ABC News: Clean Air Act
Video: ABC News: International report:
Cooling the planet
Video: ABC News: Desertification in
China
Video: ABC News: Global warming
Video: ABC News: Environmental victory
green decision
Video: ABC News: Green laws
Video: ABC News: Impacts of global
warming
Video: ABC News: International report:
Global warming
Video: ABC News: Melting ice
Video: ABC News: Miles per gallon,
requirements for automakers
Video: ABC News: MTBE pollution
Video: ABC News: Ozone layer depletion
Video: ABC News: Painful painkillers
Video: ABC News: Pharmaceuticals in
water supplies
Video: ABC News: Pollution and
women‘s health
Video: ABC News: Sports franchise
going green
Video: ABC News: Stuff that we leave
behind
Video: ABC News: Water pollution
threatens millions
Video: ABC News: U.S. forests
Video: ABC News: Wal-Mart goes green
18.6 Maintaining Biodiversity
 Biodiversity includes diversity of genes, species,
and ecosystems
 Worldwide, biodiversity is declining at all levels
 Biodiversity
• Genetic diversity of individuals of a species,
variety of species, and variety of ecosystems
Is Biodiversity Important?
 Healthy ecosystems are essential to humans
• Ecosystems produce oxygen, remove CO2,
decompose waste, provide food, prevent erosion
and flooding
 We benefit from biodiversity
• Wild species provide medicines, reservoirs of
genetic diversity to enhance crops
• Ethical reasons to preserve biodiversity
Indicator Species
 A decline in biodiversity warns us that our
natural support system is in trouble
 Indicator species
• A species that is particularly sensitive to
environmental changes and can be monitored to
assess whether an ecosystem is threatened
• Examples: lichens, mayflies
Conservation Biology
 Conservation biologists identify threatened
regions with high biodiversity and prioritize which
will receive protection
 Conservation biology
• Field of applied biology that surveys biodiversity
and seeks ways to maintain and use it
Hot Spots
 By focusing on hot spots rather than on
individual species, scientists hope to maintain
ecosystems that sustain biological diversity
 Hot spots
• Threatened regions with great biodiversity
• Considered a high priority for conservation efforts
• Currently 867 land regions identified by WWF
Protecting a Hot Spot
 Monteverde Cloud Forest Reserve, Costa Rica
Ecological Restoration
 Ecological restoration can help actively re-create
or renew a diverse natural ecosystem that has
been destroyed or degraded
 Ecological restoration
• Actively altering an area in an effort to restore or
create a functional ecosystem
• Example: Louisiana’s coastal marshes
Ecological Restoration
 Marsh restoration project, Louisiana
Living Sustainably
 Individuals can help maintain biodiversity by
using resources in a sustainable fashion
• Cut consumption
• Reuse and recycle materials
• Reduce energy use
 Sustainable development
• Using resources in a way that takes into account
the needs of future generations
Video: ABC News: Bald Eagle off
endangered list
Video: ABC News: Endangered turtles
return to sea
Video: ABC News: Natural wonders
Hawaiian Islands
Video: ABC News: Hsing Hsing dies
Video: ABC News: Marine sanctuary
Video: ABC News: Planet Earth 2007
Video: ABC News: U.S. earth summit
Video: ABC News: Penguin rescue
Video: ABC News: Whaling
18.7 Impacts/Issues Revisited
 Arctic ice sheets are breaking up due to global
climate change, making fossil fuel and mineral
resources more accessible
 However, extracting these resources will harm
species such as the polar bear, already
threatened by global climate change
Digging into Data:
Arctic PCB Pollution