Climate and Biodiversity Chapter 7
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.
Al Gore on YouTube… Inconvenient short version… http://www.youtube.com/watch?v=splKGWuErnM&feature=related Section 7-1 WHAT FACTORS INFLUENCE CLIMATE?
The earth has many different climates • Weather is a set of physical conditions ( such as ??? ) 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 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: 1. Uneven heating of earth’s surface by the sun. 2. Rotation of the earth on its axis. 3. Properties of air, water, and land.
Global air circulation
Energy is transferred by convection in the atmosphere
Deep and shallow ocean currents
Earth’s climate zones, major ocean currents, and upwelling areas
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.
The rain shadow effect
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 (H 2 O). – Carbon dioxide (CO 2 ). – Methane (CH 4 ). – Nitrous oxide (N 2 O).
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.
Section 7-2 HOW DOES CLIMATE AFFECT THE NATURE AND LOCATION OF BIOMES?
Average precipitation and temperature are determining factors
Biomes and climate both change with elevation and latitude
The earth’s major biomes
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 .
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
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
Intensively cultivated cropland
Some components and interactions in an arctic tundra ecosystem
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
Specialized plant and animal niches are stratified in a tropical rain forest
Components and interactions in a temperate deciduous forest ecosystem in North America
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?
Section 7-3 How have human activities 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.
Major human impacts on terrestrial ecosystems
Section 7-4 WHAT ARE THE MAJOR TYPES OF AQUATIC SYSTEMS?
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
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