The BiosphereClimate and Biomes

• You’ve probably heard a lot about Global Climate Change (sometimes called Global Warming).

• What is climate?

• What effects can a changing climate have on living organisms?

• Suppose your region has an especially hot summer, followed by a very cold winter that includes a snowstorm. Does this support, disprove, or have little to do with Global Climate Change?

DAILY

WORK

Climate• Climate is not the same thing as

weather!• Climate consists of the prevailing

weather patterns in a region over longs periods of time.

• Climate is caused by many factors, including location on the globe, nearness to an ocean, wind direction, geography.

90° N

90° S

NorthPole

SouthPole

0°

0°

23.5°tilt

equator

June 21st :northern summersolstice; southernwinter solstice

December 21st :northern wintersolstice; southernsummer solstice

23.5°tilt

Summer in theNorthernHemisphere

Summer in theSouthernHemisphere

The sun drives climate as well as the seasons.

• Average temperature at any part of the globe is affected not by how close we are to the sun (a common misconception) but by the angle of incidence of the sun’s rays.

Less direct rays = less solar energy =

cooler region

More direct rays = more solar energy =

warmer region

• Global air circulation influences local climates.

• Rising air cools and drops moisture.

• Descending air tends to be dry.

cool, moistair rises(rain/snow)

warm, dryair falls

PolarEasterlies

hot,moistair rises(rain)

warm, dryair falls

cool, moistair rises(rain/snow)

polar cap90 S

60 S

30 S

30 N

90 Npolar cap

cold, dryair falls

60 N

0

Westerlies

S.E.Tradewinds

N.E.Tradewinds

rainforest

desert

rotation

Westerlies

PolarEasterlies

desert

rainforest

cold, dryair falls

• According to this diagram, where on the planet should we find:

• Deserts?

• Tropical rain forests?

• Permanent snowfields?

DAILY

WORK

A. Cool, moist, rising air

B. Warm, dry,

falling air

C. Warm, moist, rising

air

• Ocean current also affect climate.

• Water tends to absorb and retain heat, and lose it slowly.

• Ocean water near the equator tends to be warm, so currents from the equator are warm.

• Water near the poles is much cooler.

• The Gulf Stream carries warm water from the equator northward, warming the coast of Europe.

• There is evidence that the Greenland ice is melting, due to Global Climate Change, and pouring cold water into the North Atlantic. If this happens what will happen to the climate of Northern Europe?

moist climate

dry climate inrain shadow

Water is carriedfrom ocean byprevailing winds.

Water is releasedas air rises andcools.

Dry air sinks,warms andabsorbs waterfrom the land.

altit

ude

low

high

latitudeequator

(0°)poles(90°)

deciduousforest

tundra

rock, snow, ice

coniferousforest

tropicalforest

Biomes• The concept of “biome” is

controversial.• What “biomes” an ecology text

describes depends on how fine-grained the divisions are.

• At the broadest view, there are six major biomes.

Major Biomes• Hot, dry = hot desert• Hot, wet = tropical rain forest• Warm, dry = grasslands• Warm, wet = temperate deciduous

forest• Cold, dry = tundra, cold desert• Cold, wet = northern boreal forests

(taiga)

Tem

pera

ture

Rainfall

high

high

low

low

savanna tropicalrain forest

tropicaldeciduous forest

warmgrassland

warmdesert

temperate rain foresttemperatedeciduous forest

cool grasslandcool desert

coniferous forest (taiga)

tundra

Desert• Deserts may be hot or cold, though

hot deserts have a different structure than cold deserts.

• Deserts are characterized by low rainfall.

• When rain does fall, it often falls “all at once,” and runs off.

Sagebrush Desert, Utah

Mojave Desert, California

Sahara Desert, Northern Africa

Where is this?

A dry valley in Antarctica!Not all deserts are hot!

And even “hot” deserts aren’t always hot.

Snow in the Mojave

Tropical Rain Forest• Characterized by a warm climate and

high rainfall.• Very high biodiversity.• Forest structure may include multiple

layers: floor, understory, canopy, and emergent layers.

• Soil layer is thin, because organic material decays quickly and is taken up by plants.

Tropical Rain Forests

Mists over a tropical rain forest

Grassland• Grasslands, shrublands, and dry

woodlands are characterized by:• Low to moderate rainfall (semi-

arid)• Warm to hot summers, cold

winters• Prairies may have deep, rich soil

Shortgrass prairie, South Dakota

Zhongdian Steppe, Tibet

Prairie habitats are fire-based ecosystems.

Temperate Deciduous Forest

• Deciduous forests grow in temperate regions with moderate rainfall that also tend to have wet summers.

• Trees drop their leaves before the cold winters.

• The open spring canopy allows a flush of spring wildflowers before the trees leaf out again.

Mohican State Memorial Forest, Ohio

Oak-Hickory forest, Missouri

Northern Boreal Forest• Coniferous forests are favored

where there are either dry seasons or harsh winters, or both.

• Needle-shaped leaves with waxy coats can endure harsh, cold winds in northern climates and on mountains.

• Needle-leaved conifers are also found near oceans, where harsh salt spray can dry out plants.

High winter rainfall can create temperate rainforests in this biome, such as the Hoh Rainforest in

Washington.

Where there is less rainfall, the trees are more sparse, as in this taiga forest in Alaska.

Tundra

• Arctic tundra is characterized by permafrost, shrubby vegetation, and sometimes bogs.

• Alpine tundra usually does not have permafrost, but does feature alpine meadows or shrubby vegetation, and no trees.

Arctic tundra in the Arctic National Wildlife Refuge

Alpine tundra on Mt. Rainier

Ocean Biomes• Oceans are often divided into zones

just as the land is, including:• Estuary• Intertidal zone• Continental shelf• Open ocean• Hydrothermal vents

plankton photiczone

200 m

aphoticzone

open ocean

intertidalzone

near-shorezone

Estuary

Intertidal zone: Rocky

Intertidal zone: sandy

Continental Shelf

Reef

Open Ocean

Deep Ocean

Hydrothermal Vents