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

Fig. 18-5c, p. 365

Grassland, shrublands, and woodlands

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

Fig. 18-10a, p. 369

air at ocean surface

water of the open ocean water over continental shelf

continental shelf

sunlit water“twilight” water

0Pelagic Province

sunless water

200

1,000

2,000

4,000

Benth

ic P

rovi

ncedeep-sea trenches11,000

depth (meters)

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 coal-

burning 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