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The Biosphere. Climate 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?
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The Biosphere • Climate 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? D A I L Y W O R K
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.
The sun drives climate as well as the seasons. Summer in the Northern Hemisphere North Pole 90° N 23.5° tilt 0° equator 0° 23.5° tilt Summer in the Southern Hemisphere 90° S South Pole December 21st : northern winter solstice; southern summer solstice June 21st : northern summer solstice; southern winter solstice
Less direct rays = less solar energy = cooler region • 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. More direct rays = more solar energy = warmer region
cold, dry air falls cool, moist air rises (rain/snow) Polar Easterlies 90 N polar cap 60 N • Global air circulation influences local climates. • Rising air cools and drops moisture. • Descending air tends to be dry. Westerlies warm, dry air falls 30 N desert N.E. Tradewinds hot, moist air rises (rain) rain forest rotation 0 S.E. Tradewinds rain forest desert 30 S warm, dry air falls Westerlies 60 S Polar Easterlies polar cap 90 S cool, moist air rises (rain/snow) cold, dry air falls
A. Cool, moist, rising air • According to this diagram, where on the planet should we find: • Deserts? • Tropical rain forests? • Permanent snowfields? D A I L Y W O R K 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?
Water is released as air rises and cools. Dry air sinks, warms and absorbs water from the land. Water is carried from ocean by prevailing winds. dry climate in rain shadow moist climate
high rock, snow, ice tundra coniferous forest deciduous forest altitude tropical forest low equator (0°) poles (90°) latitude
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)
low tundra coniferous forest (taiga) Temperature cool desert cool grassland temperate deciduous forest temperate rain forest high warm desert warm grassland savanna tropical deciduous forest tropical rain forest low Rainfall high
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.
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.
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
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.
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.
Ocean Biomes • Oceans are often divided into zones just as the land is, including: • Estuary • Intertidal zone • Continental shelf • Open ocean • Hydrothermal vents
intertidal zone near-shore zone open ocean photic zone plankton 200 m aphotic zone
