Climate and Biodiversity Chapter 7. WHAT FACTORS INFLUENCE CLIMATE? Section 7-1.

Climate and Biodiversity

Chapter 7

WHAT FACTORS INFLUENCE CLIMATE?

Section 7-1

The earth has many different climates

• 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.

• Climate is an area’s general pattern of atmospheric conditions over periods ranging from 30 to thousands of years.

• Earth’s current major climate zones and ocean currents are key components of the earth’s natural capital.

The earth has many different climates

• Climate varies in different parts of the earth primarily because global air circulation and ocean currents distribute heat and precipitation unevenly between the tropics and other parts of the world.

• Three major factors determine how air circulates in the lower atmosphere:– Uneven heating of earth’s surface by the sun.– Rotation of the earth on its axis. – Properties of air, water, and land.

Earth’s climate zones, major ocean currents, and upwelling areas

Fig. 7-2, p. 123

Polar (ice) Subarctic (snow) Cool temperate Highland Warm ocean current River

Warm temperate Dry Tropical Major upwelling zones

Cold ocean current

ArcticCircle

Tropic ofCancer

Tropic ofCapricorn

AntarcticCircle

The earth has many different climates

• 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.

• El Niño–Southern Oscillation, or ENSO—is an example of the interaction of land and air.– Large-scale weather phenomenon occurring every few years

when prevailing winds in the tropical Pacific Ocean weaken and change direction.

– Above-average warming of Pacific waters can affect populations of marine species by changing the distribution of plant nutrients.

Global air circulation

Fig. 7-3, p. 123

Moist air rises, cools, and releases moisture as rain

Cold desertsCold deserts60°NEvergreen coniferous forest

Evergreen coniferous forest

The highest solar energy input is at the equator.

Hot desertHot desertNortheast trades

30°NTemperate deciduous forest and grasslandTemperate deciduous forest and grassland

WesterliesWesterlies

Air cools and descends at lower latitudes.

Tropical deciduous forestTropical deciduous forest

Warm air rises and moves toward the poles.

Solar energy

Equator 0°Tropical rain forestTropical rain forest

Tropical deciduous forestTropical deciduous forest

Southeast trades Hot desertHot desert

30°SWesterliesWesterlies

60°SCold desertsCold deserts

Temperate deciduous forest and grassland

Temperate deciduous forest and grassland

Air cools and descends at lower latitudes.

Polar capPolar cap

Polar capPolar cap

Energy is transferred by convection in the atmosphere

Fig. 7-4, p. 124

Cool, dry air

Condensation and

precipitation

Heat released radiates to space

LOW PRESSURE

HIGH PRESSURE

Falls, is compressed, warms

Rises, expands,

cools

Warm, dry air

Hot, wet airFlows toward low

pressure, picks up moisture and heat

HIGH PRESSURE

Moist surface warmed by sun

LOW PRESSURE

Deep and shallow ocean currents

Fig. 7-5, p. 124

Warm, less salty, shallow current

Warm, less salty, shallow current

Cold, salty, deep current

Greenhouse gases warm the lower atmosphere

• Greenhouse gases absorb and release heat, which warms the atmosphere, influencing the earth’s average temperatures and its climates.

• The major greenhouse gases are:– Water vapor (H2O).

– Carbon dioxide (CO2).

– Methane (CH4).

– Nitrous oxide (N2O).

Greenhouse gases warm the lower atmosphere

• 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.

The earth’s surface features affect local climates

• Heat is absorbed and released more slowly by water than by land, creating land and sea breezes.

• Mountains interrupt the flow of prevailing surface winds and the movement of storms.

• High mountains create the rain shadow effect.

• Cities with bricks, asphalt, and traffic create distinct microclimates.

The rain shadow effect

Fig. 7-6, p. 125

Prevailing winds pick up moisture from an ocean.

On the windward side of a mountain range, air rises, cools, and releases moisture.

On the leeward side of the mountain range, air descends, warms, and releases little moisture, causing rain shadow effect.

HOW DOES CLIMATE AFFECT THE NATURE AND LOCATION OF BIOMES?

Section 7-2

Climate helps to determine where organisms can live

• Average annual precipitation and temperature lead to the formation of tropical (hot), temperate (moderate), and polar (cold) deserts, grasslands, and forests.

• Climate and vegetation vary with latitude and elevation.

• Biomes are large regions, each characterized by certain types of climate and dominant plant life.

• Biomes are not uniform. They consist of a mosaic of patches, each with somewhat different biological

communities but with similarities typical of the biome.

Average precipitation and temperature are determining factors

Fig. 7-7, p. 127

Cold

Arctic tundra

Cold desertEvergreen coniferous forest

Temperate desertTemperate deciduous forest

Temperate grasslandChaparral

Hot WetHot Wet

Tropical rain forestDry

Tropical desert

Tropical grassland (savanna)

Biomes and climate both change with elevation and latitude

Fig. 7-8, p. 127

Elevation Mountain ice and snow

Tundra (herbs, lichens, mosses)

ConiferousForest

DeciduousForest

Latitude (south to north)

TropicalForest

Tropical Forest

Deciduous Forest

Coniferous Forest

Tundra (herbs, lichens, mosses)

Polar ice and snow

The earth’s major biomes

Fig. 7-9, p. 128

Tropic of Cancer

High mountainsEquator

Polar iceArctic tundra (cold grassland)

Temperate grassland Tropic of CapricornTropical grassland (savanna)

Chaparral

Coniferous forestTemperate deciduous forest

Temperate rain forest

Tropical rain forest

Tropical dry forest

Desert

There are three major types of desert

• 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.

• Tropical deserts are hot and dry most of the year, with few plants.

• Temperate deserts have high daytime temperatures in summer and low in winter. Sparse vegetation is mostly cacti and other succulents.

There are three major types of desert

• Cold deserts have sparse vegetation, cold summers and precipitation is low.

• 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.

Typical variations in annual temperature (red) and precipitation (blue) in deserts

Stepped Art

Fig. 7-10, p. 129

There are three major types of grasslands

• Grasslands occur mostly in the interiors of continents in areas too moist for deserts and too dry for forests.

• Grasslands are not taken over by shrubs and trees because of seasonal droughts, grazing by large herbivores, and occasional fires.

There are three major types of grasslands

• The three main types of grassland:– Tropical (e.g. savanna): Savanna contains widely scattered

clumps of trees and is usually warm year-round with alternating dry and wet seasons

– Temperate (e.g. short-grass and tall-grass prairies):Temperate grassland winters can be very cold, summers are hot and dry, and annual precipitation is fairly sparse and falls unevenly through the year.

– Cold (e.g. 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.

Typical variations in annual temperature (red) and precipitation (blue) in grasslands

Stepped Art

Fig. 7-11, p. 131

Intensively cultivated cropland

Some components and interactions in an arctic tundra ecosystem

Fig. 7-13, p. 133

Long-tailed jaegerLong-tailed jaeger

CaribouCaribou

Grizzly bearGrizzly bear

MosquitoMosquito

Horned larkHorned lark

Arcticfox

Arcticfox

Snowy owlSnowy owl

Dwarf willowDwarf willow

Willow ptarmiganWillow ptarmigan

LemmingLemming

MountaincranberryMountaincranberryFungiFungi

Producer to primary consumer

Primary to secondary consumer

Secondary to higher-level consumer

All producers and consumers to decomposers

BacteriaBacteria

Moss campionMoss campion

There are three major types of forests

• Forests are lands dominated by trees.

• The three main types of forest:– Tropical: Found near the equator with a warm and

wet climate; ideal for a wide variety of plants and animals.

• Dominated by broadleaf evergreen plants keep most of their leaves year-round. There is little vegetation on the forest floor because the dense tree-top canopy blocks most light from reaching the ground.

• Very high net primary productivity and an incredible high level of biological diversity.

There are three major types of forests

• Cover about 2% of the earth’s land surface but are estimated to contain at least 50% of the earth’s known terrestrial plant and animal species

– Temperate: • Cool temperatures slow decomposition, so have a

thick layer of slowly decaying leaf litter which is a storehouse of nutrients

– Cold: northern coniferous (cone-bearing) and boreal.

• Winters are long and extremely cold. Plant diversity is low, decomposition is slow.

Typical variations in annual temperature (red) and precipitation (blue) in forests

Stepped Art

Fig. 7-14, p. 134

Specialized plant and animal niches are stratified in a tropical rain forest

Fig. 7-15, p. 135

45

Harpy eagle

Emergent layer

40

35Toco toucan

30Canopy

25

Hei

gh

t (m

eter

s)

20Wooly opossum

Understory

15

10

Brazilian tapir

Shrub layer5

Black-crowned antpitta

Ground layer

0

Components and interactions in a temperate deciduous forest ecosystem in North America

Fig. 7-16, p. 136

Broad-winged hawkBroad-winged hawk

White-taileddeerWhite-taileddeer

Hairy woodpecker

Hairy woodpecker

White oakWhite oak

Mountainwinterberry

MountainwinterberryShagbark

hickoryShagbark hickory

White-footedmouseWhite-footedmouse

Metallic wood-boring beetle and larvae

Metallic wood-boring beetle and larvae

Black racer snake

Black racer snake

BacteriaBacteria

May beetleMay beetle

FungiFungi

Producer to primary consumer

Primary to secondary consumer

Secondary to higher-level consumer

All producers and consumers to decomposers

Wood frogWood frog

Long-tailed weaselLong-tailed weasel

Mountains play important ecological roles

• Mountains are steep or high-elevation lands where dramatic changes in altitude, slope, climate, soil, and vegetation take place over a very short distance.

• About 1.2 billion people (17% of the world’s population) live in mountain ranges or their foothills, and 4 billion people (57% of the world’s population) depend on mountain systems for all or some of their water.

• Many mountains are islands of biodiversity surrounded by a sea of lower-elevation landscapes transformed by human activities.

Mountains play important ecological roles

• Important ecological roles include:– Contain the majority of the world’s trees– Provide habitats for endemic species– Have sanctuaries for species that can migrate and

surviving in higher altitudes if they are driven from lowlands by human activities or a warming climate..

• Mountains play a critical role in the hydrologic cycle by serving as major storehouses of water.

How have human activities affected the world’s terrestrial ecosystems?

Section 7-3

Humans have disturbed most of the earth’s land

• About 62% of the world’s major terrestrial ecosystems are being degraded or used unsustainably.

Major human impacts on terrestrial ecosystems

Fig. 7-18, p. 138

Natural Capital DegradationMajor Human Impacts on Terrestrial Ecosystems

Deserts Grasslands Forests Mountains

Large desert cities Conversion to cropland

Clearing for agriculture, livestock grazing, timber, and urban development

Agriculture

Release of CO2 to atmosphere from burning grassland Conversion of

diverse forests to tree plantationsOvergrazing

by livestockDamage from off-road vehiclesOil production

and off-road vehicles in arctic tundra

Pollution of forest streams

Destruction of soil and underground habitat by off-road vehicles

Depletion of groundwater

Land disturbance and pollution from mineral extraction

Timber and mineral extraction

Hydroelectric dams and reservoirs

Air pollution blowing in from urban areas and power plants

Soil damage from off-road vehicles

Fig. 7-18, p. 138

Natural Capital DegradationMajor Human Impacts on Terrestrial Ecosystems

Large desert cities

Deserts

Destruction of soil and underground habitat by off-road vehicles

Depletion of groundwater

Land disturbance and pollution from mineral extraction Stepped Art

Grasslands

Conversion to cropland

Release of CO2 to atmosphere from burning grassland

Overgrazing by livestock

Oil production and off-road vehicles in arctic tundra

Forests

Clearing for agriculture, livestock grazing, timber, and urban development

Conversion of diverse forests to tree plantations

Damage from off-road vehicles

Pollution of forest streams

Mountains

Agriculture

Timber and mineral extraction

Hydroelectric dams and reservoirs

Air pollution blowing in from urban areas and power plants

Soil damage from off-road vehicles

WHAT ARE THE MAJOR TYPES OF AQUATIC SYSTEMS?

Section 7-4

Most of the earth is covered with water

• About 71% of the earth’s surface is covered with salty ocean water.

• One global ocean, divided it into four large areas by geographers.– Atlantic Ocean.– Pacific Ocean.

• The largest; contains more than half of the earth’s water and covers one-third of the earth’s surface.

– Arctic Ocean.– Indian Ocean.

The ocean planet

Fig. 7-19, p. 139

Ocean hemisphere Land–ocean hemisphere

Most of the earth is covered with water

• Aquatic life zones are the aquatic counterparts of biomes

• 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.

• Zones are classified into two major types: – Saltwater or marine life zones: Oceans and their bays,

estuaries, and other coastal systems.

– Freshwater life zones: Lakes, rivers, streams, and inland wetlands.

Most of the earth is covered with water

• Four major types of aquatic organisms:– Plankton are weakly swimming and free-

floating. Types include:• Phytoplankton: photosynthesizers, includes many

types of algae.• Zooplankton: plankton that feed on other plankton. • Ultraplankton: huge populations of photosynthetic

bacteria.

– Nekton are strong-swimming consumers such as fish, turtles, and whales.

Most of the earth is covered with water

– Benthos are bottom dwellers. Examples include:

• Oysters, which anchor themselves to one spot.• Clams and some worms, which burrow into the

bottom.• Lobsters and crabs, which walk on the sea floor.

– Decomposers (mostly bacteria), which break down organic compounds in the dead bodies and wastes of aquatic organisms.

Most of the earth is covered with water

• Key factors determining the type and number of organisms at various depths include:– Water temperature.– Dissolved oxygen content.– Availability of food.– Availability of light and nutrients required for

photosynthesis.

WHY ARE MARINE AQUATIC SYSTEMS IMPORTANT AND HOW HAVE WE AFFECTED THEM?

Section 7-5

Marine ecosystems

Oceans provide vital ecological and economic services

• Enormous reservoirs of biodiversity with three major life zones: The coastal zone, open sea and ocean bottom.

• The coastal zone – Warm, nutrient-rich, shallow water that extends from the

high-tide mark on land to the edge of the continental shelf.

– 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.

– Have high net primary productivity due to ample sunlight and plant nutrients that flow from land.

Major life zones and vertical zones in an ocean

Fig. 7-21, p. 141

High tideLow tide

Coastal Zone

Open Sea Depth in

metersSea level

50Estuarine Zone

Euphotic Zone

100

Ph

oto

syn

thes

is

Continental shelf

200

500Bathyal Zone

1,000

Tw

ilig

ht

1,500

Water temperature drops rapidly between the euphotic zone and the abyssal zone in an area called the thermocline .

Abyssal Zone

2,000

3,000

4,000

Dar

knes

s

5,000

10,000

0 5 10 15 20 25 30Water temperature (°C)

0

Estuaries and coastal wetlands are highly productive

• 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.

• Associated coastal wetlands are areas covered with water all or part of the year. – Coastal wetlands are in temperate zones.

– Mangrove forests are in tropical zones.

• Some of the earth’s most productive ecosystems.

Estuaries and coastal wetlands are highly productive

• Sea grass beds consist of plants that grow underwater in shallow marine and estuarine areas along most continental coastlines.

• Coastal aquatic systems provide vital ecological and economic services such as: – Help maintain water quality in tropical coastal zones by filtering

toxic pollutants, excess plant nutrients, and sediments, and by absorbing other pollutants.

– Provide food, habitats, and nursery sites for a variety of aquatic and terrestrial species.

– Reduce storm damage and coastal erosion by absorbing waves and storing excess water produced by storms and tsunamis.

Estuary in Madagascar

Coral reefs are storehouses of biodiversity

• Underwater structures that are built primarily of limestone and form in the clear, warm coastal waters of the tropics and subtropics.

• Highly productive ecosystems that are dazzling centers of biodiversity.

• Reefs form from massive colonies of polyps that secrete limestone.

• Coral reefs result from a mutually beneficial relationship between the polyps and single-celled algae called zooxanthellae that live in the tissues of the polyps.

Coral reefs are storehouses of biodiversity

• Ecological services provided by coral reefs include:– Act as natural barriers that help to protect 15%

of the world’s coastlines from erosion caused by waves and storms.

– Provide habitats for about 25% of all marine organisms.

– Produce about 10% of the global fish catch.– Provide fishing and ecotourism jobs for some of

the world’s poorest countries.

Coral reefs are storehouses of biodiversity

• Coral reefs are easily damaged because they grow slowly, are disrupted easily and require specific water conditions.

• 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.

A healthy coral reef and a bleached one

Coral reefs are storehouses of biodiversity

• Ocean water is becoming more acidic as it absorbs some of excess carbon dioxide from the atmosphere. The CO2 reacts with ocean water to form a weak acid, which can slowly dissolve the calcium carbonate that makes up the corals.

• Almost 45–53% of the world’s shallow coral reefs have been destroyed or degraded by coastal development, pollution, overfishing, warmer ocean temperatures, increasing ocean acidity, and other stresses.

The open sea and the ocean floor host a variety of species

• 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.– The euphotic zone is the brightly lit upper zone, where

drifting phytoplankton carry out about 40% of the world’s photosynthetic activity.

– The bathyal zone is the middle zone, which gets little sunlight and therefore does not contain photosynthesizing producers.

– The lowest zone, called the abyssal zone, is dark and very cold; it has little dissolved oxygen.

Human activities are disrupting and degrading marine ecosystems

• About 45% of the world’s population and more than half of the U.S. population live along or near coasts.

• Major threats to marine systems from human activities include:– Coastal development, which destroys and pollutes

coastal habitats. – Runoff of nonpoint source pollution such as fertilizers,

pesticides, and livestock. – Point-source pollution such as sewage from passenger

cruise ships and spills from oil tankers.

Human activities are disrupting and degrading marine ecosystems

– Overfishing, which depletes populations of commercial fish species.

– Use of trawler fishing boats, which drag weighted nets across the ocean bottom and destroy habitats.

– Invasive species, some introduced by humans, that can out compete populations of native aquatic species and cause economic damage.

– Climate change which is warming the oceans and making them more acidic; this could cause a rise in sea levels during this century that would destroy coral reefs and flood coastal marshes and coastal cities.

Major threats to marine ecosystems by humans

WHAT ARE THE MAJOR TYPES OF FRESHWATER SYSTEMS AND HOW HAVE HUMAN ACTIVITIES AFFECTED THEM?

Section 7-6

Water stands in some freshwater systems and flows in others

• Freshwater life zones include standing bodies of freshwater such as lakes, ponds, and inland wetlands, and flowing (lotic) systems such as streams and rivers.

• Lakes are large natural bodies of standing freshwater formed when precipitation, runoff, streams and rivers, and groundwater seepage fill depressions.

• Oligotrophic (poorly nourished) lakes have a small supply of plant nutrients, causing them to look crystal clear.

Water stands in some freshwater systems and flows in others

• Eutrophic (well-nourished) lakes have a large supply of nutrients needed by producers, causing them 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.

Freshwater systems provide many important services

Typical distinct zones of life in fairly deep temperate-zone lakes

Fig. 7-28, p. 146

Painted turtle

Blue-winged teal

Green frog

Muskrat

Pond snail

Littoral zone Plankton

Diving beetle Northern

pike

Yellow perch Bloodworms

The effect of nutrient enrichment on a lake

Freshwater streams and rivers carry water from the mountains to the oceans

• Surface water becomes runoff when it flows into streams or lakes.

• A watershed, or drainage basin, is the land area that delivers runoff, sediment, and dissolved substances to a stream or lake.

• The downward flow of water from mountain highlands to the sea typically takes place in three aquatic life zones characterized by different environmental conditions: – The source zone, the transition zone, and the floodplain

zone.

Three zones in the downward flow of water

Fig. 7-30, p. 147

Lake GlacierHeadwatersRain and

snowRapids

WaterfallTributary

Flood plain Oxbow lakeSalt marsh

DeltaDeposited sediment

Source ZoneOcean

Transition Zone

SedimentWater

Floodplain Zone

Freshwater inland wetlands are vital sponges

• Inland wetlands are lands covered with freshwater all or part of the time and located away from coastal areas.– Marshes (mainly grasses, reeds, and few trees).– Swamps (dominated by trees and shrubs).– Prairie potholes (depressions carved out by ancient

glaciers).– Floodplains (receive excess water during heavy rains and

floods).– Seasonal wetlands (remain under water or are soggy for

only a short time each year).– Arctic tundra (wet in summer).

Freshwater inland wetlands are vital sponges

• Inland wetlands provide a number of free ecological and economic services, which include:– Filtering and degrading toxic wastes and

pollutants.– Reducing flooding and erosion by absorbing

storm water and releasing it slowly, and by absorbing overflows from streams and lakes.

– Maintaining stream flows during dry periods.– Helping to recharge groundwater aquifers

Freshwater inland wetlands are vital sponges

– Helping to maintain biodiversity by providing habitats for a variety of species,

– Supplying valuable products such as fishes and shellfish, blueberries, cranberries, wild rice, and timber, and

– Providing recreation for birdwatchers, nature photographers, boaters, anglers, and waterfowl hunters.

Human activities are disrupting and degrading freshwater systems

• 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.

• 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.

• 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.

Human activities are disrupting and degrading freshwater systems

• Many inland wetlands have been drained or filled to grow crops or have been covered with concrete, asphalt, and buildings.

• More than 50% of the inland wetlands in the continental United States have been lost which has increased flood damage in the United States.

Three big ideas

• Differences in climate, based mostly on long-term differences in average temperature and precipitation, largely determine the types and locations of the earth’s deserts, grasslands, and forests.

• Saltwater and freshwater aquatic systems cover almost three-fourths of the earth’s surface, and oceans dominate the planet.

• The earth’s terrestrial and aquatic systems provide important ecological and economic services, which are being degraded and disrupted by human activities.