Chapter 7 – Climate and Biodiversity

Core Case Study: Different Climates Support Different Life Forms

• The Earth has a great diversity of species and habitats.

• Differences in climate result mostly from long-term differences in average annual precipitation and temperature.

Core Case Study: Different Climates Support Different Life Forms (cont.)

• Climate matters because it determines where humans and other species can live and thrive.

• When the climate changes there is usually a shift in location of areas where food can be grown and where species can live.

7-1 – What Factors Influence Climate?

The Earth Has Many Different Climates

• Weather is a set of physical conditions of the lower atmosphere such as temperature, precipitation, humidity, wind speed, and cloud cover.

• Climate is an area’s general pattern of atmospheric conditions over periods of at least three decades and up to thousands of years.

The Earth Has Many Different Climates (cont.)

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

Greenhouse Gases Warm the Lower Atmosphere

• Greenhouse gases allow mostly visible light and some infrared radiation and ultraviolet radiation from the sun to pass through the atmosphere.

• Burning fossil fuels, clearing forests, and growing crops release carbon dioxide, methane and nitrous oxide into the atmosphere.

Greenhouse Gases Warm the Lower Atmosphere (cont.)

Earth’s Surface Features Affect Local Climates

• Heat is absorbed and released more slowly by water than land.

• The rain shadow effect is when the resulting semiarid or arid conditions on the leeward side of a high mountain.

7-2 – How Does Climate Affect the Nature and Location of Biomes

Climate Helps to Determine Where Organisms Can Live

• Differences in climate explain why global air circulation patterns account for different types of deserts, grasslands, and forests.

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

There Are Three Major Types of Deserts

• Deserts have low annual precipitation and it is often scattered unevenly throughout the year.

• Tropical deserts are hot and dry most of the year.

• Temperate deserts have high daytime temperatures during the summer and low daytime temperatures in the winter.

There Are Three Major Types of Deserts (cont.)

• Cold deserts have sparse vegetation.

There Are Three Major Types of Grasslands

• Grasslands occur mostly in the interiors of continents in areas that are too moist for deserts to form and too dry for forests to grow.

• Temperate grasslands have bitterly cold winters, and hot and dry summers.

• Cold grasslands, or arctic tundra, are bitterly cold and usually have no trees.

• Tropical grasslands contain widely scattered clumps of trees which are covered with thorns that keep some herbivores away.

There Are Three Major Types of Grasslands (cont.)

There Are Three Major Types of Forests

• Forests are lands dominated by trees.• Tropical rain forests are found near the

equator where hot, moist air rises and dumps its moisture.

• Temperate deciduous forests grow in areas with moderate average temperatures that change significantly with the seasons.

There Are Three Major Types of Forests (cont.)

• Evergreen coniferous forests, also called boreal forests and taigas, are cold forests that are found just south of the arctic tundra in northern regions across North America, Asia, and Europe.

Mountains Play Important Ecological Roles

• About 1.2 billion people live in mountain ranges, and 4 billion people depend on mountain systems for all or some of their water.

• Mountains contain the majority of the world’s forests, which are habitats for much of the planet’s terrestrial biodiversity.

Mountains Play Important Ecological Roles (cont.)

• Mountains serve as sanctuaries for animal species that are capable of migrating to higher altitudes and surviving in such environments.

7-3 – How Have We Affected the World’s Terrestrial Ecosystems?

Humans Have Disturbed Most of the Earth’s Land

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

• If we increase the stresses on some of these biomes, such as by clearing tropical forests, they could be replaces by grasslands in many areas, which would represent massive loss of biodiversity.

Humans Have Disturbed Most of the Earth’s Land (cont.)

• Loss of biodiversity would reduce the vegetation needed to remove some of the excess carbon dioxide that we add to the atmosphere.

7-2 Science Focus – Staying Alive in the Desert

• Every drop of water counts for survival in the desert.

• Desert plants have evolved to adapt to the heat, save more and use less water.

• Some desert plants use deep roots to tap into groundwater.

• Some plants found in deserts conserve water by having wax-coated leave that reduce water loss.

7-2 Science Focus – Staying Alive in the Desert (cont.)

7-3 Revisiting – Climate, Biodiversity, and Sustainability

• Everything in nature is connected.• Scientists believe that we urgently need more

research on the components and workings of the world’s biomes, on how they interconnected, and on which connections are the strongest and which are in the greatest danger of being disrupted by human activities.

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.

• The earth’s terrestrial systems provide important ecological and economic services

• Human activities are degrading and disrupting many of the ecological and economic services provided by the earth’s terrestrial ecosystems.