 All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things.

Human Activities  Industry and technology give humans a strong advantage in competing with other species for limited resources such as food, energy, and space. Humans are the most important source of environmental change on the planet.  Human activities can change the flow of energy in an ecosystem and reduce the ability of ecosystems to recycle nutrients. Human activities that have that have changed the biosphere are hunting and gathering, agriculture, industry, and urban development.

Hunting and Gathering  For most of human history, hunting and gathering was the primary means of survival. Early humans hunted birds and other animals and fished. They gathered seeds, fruits, and nuts. Some people were nomadic, which means they traveled to take advantage of movements and cycles of natural plant and animal populations.

Hunters and gatherers lived in small groups. They often changed the environment. They built dams to divert water and burned grasslands to encourage the growth of certain plants. Some scientists believe early human hunters caused one of the major mass extinctions of large animals (etc: woolly mammoths, giant ground sloths, sabertooth cats)

Today, groups of people in different parts of the world still follow the hunting and gathering way of life. They supplement their diet with the meat of wild animals through subsistence hunting. Subsistence hunters make few demands on the environment but use some form of technology, such as guns, snowmobiles, or tools.

Agriculture  Early hunter-gatherers planted seeds near human settlements. About 11,000 years ago, humans began farming, or agriculture. Agriculture spread in many directions as people planted other varieties of seeds. Acriculture gave people a dependable supply of food. People settled around regions of agricultural growth, creating town and cities, leading to the development of elements of civilizations such as government, laws, and writing.

Domestication of Animals  As crops improved and farming methods became more reliable, farmers began to keep herds of domesticated animals, like sheep, goats, cows, pigs, horses, and dogs. They supplied milk, meat, wool, companionship, and did work. Overgrazing by goats, cows, and others changed grassland ecosystems to eroded soils and put large demands on water supplies.

From Traditional to Modern Agriculture  Between 1450 and 1700, an exchange of foods began. In the 1800s, advancements in science and technology led to a change in agriculture. Large-scale watering (irrigation), new crop varieties, and the invention of farm machines for plowing, planting, and harvesting helped farmers to increase their yields tremendously.

The Green Revolution  By the 1950s, there was not enough food to keep up with the growing population. In a global effort to increase food production, governments and scientists developed new, intensive farming practices that greatly increased yields of rice, wheat, and other crops. This is now known as the green revolution.

The green revolution needed a few things to increase crop production. The main strategy was the development of new, highly productive varieties of major food crops. Crop breeders developed new plant varieties called “miracle strains” that improved harvests. Another strategy was a method called monoculture. Monoculture calls for large fields to be cleared, plowed, and planted with a single crop every year. Irrigation, chemical fertilizers, and pesticides are used. Farmers also replaced human and animal power with machines

 The green revolution increased food production and helped prevent food shortages.  Disadvantages: water supplies and energy depleted, pesticides carry potentially harmful chemicals, fertilizer can interfere with food webs and biogeochemical cycles.

Industrial Growth and Urban Development  Many ecologists are concerned about the effects of human activity on the environment. Some industrial processes pollute air, water, and soil.

 Resource – something that can be taken when needed  Common Resource – environmental resource owned by many people in common  Two types or resources: renewable and nonrenewable  Renewable resource – can regenerate and is therefore replaceable  Not necessarily unlimited (fresh water can become limited by drought or overuse)

 Nonrenewable resource – Can’t be replenished naturally Ex – Fossil fuels (coal, oil, gas) When these fuels are gone, they are gone forever  Sustainable use is a way of using natural resources at a rate that does not deplete them

Land Resources  Plants need fertile topsoil to grow. Plowing the land increases the rate of soil erosion – (wearing away of surface soil by water and wind)  Desertification – farming, overgrazing, and drought in dry climates turn once productive areas into deserts

Forest Resources  Forests are an important resource for the products they provide and functions they perform (wood, provide oxygen)  Deforestation – loss of forests  Can lead to severe erosion of soil  Tree farms are a renewable resource because when a tree is cut down, a new one is planted.

Ocean Resources  People depend on sea life for food. Overfishing can destroy a fishery.  Aquaculture – the farming of aquatic organisms -an efficient way to produce sea life  If not properly managed, can pollute water with fish waste and damage local aquatic ecosystems.

Air Resources  Air is a resource we use every time we breathe.  Smog – a mixture of chemicals that occurs as a gray-brown haze in the atmosphere  Pollutant – harmful material that can enter the biosphere through land, air, or water  Burning fossil fuels can release pollutants that cause smog. Burning fossil fuels releases acidic gases into the air and form drops of nitric and sulfuric acids and fall as acid rain - can kill plants

Water Resources Americans use billions of gallons of fresh water daily for everything from drinking and washing to watering crops and making steel. Although water is renewable, the total supply of fresh water is limited. Protecting water supplies from pollution and managing society’s ever-growing demand for water are major priorities. As demand for water grows rapidly in many parts of the US, water conservation is becoming an increasingly important aspect of sustainable use.

6-3 BIODIVERSITY

 Biodiversity – the sum total of the genetically based variety of all organisms in the biosphere  Ecosystem diversity - the variety of habitats, communities, and ecological processes in the living world  Species diversity – the number of different species in the biosphere  So far, biologists have identified and named about 1.5 million species and estimate that milllions more may be discovered in the future.

 Genetic diversity – the sum total of all the different forms of genetic information carried by all organisms living on the earth today.  Biodiversity is one of Earth’s greatest natural resources. Species of many kinds have provided us with foods, industrial products, and medicines

Threats to Biodiversity  Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species to new environments.  As human activities change ecosystems, this may lead to the extinction of species. (no longer exists)  Endangered species – a species whose population is declining in a way that places it in danger.

Habitat Alteration and Fragmentation When land is developed, natural habitats may be destroyed. As habitats disappear, the species that live in those habitats vanish. Development often splits ecosystems into pieces. This is called habitat fragmentation.

Conserving Biodiversity  Conservation – the wise management of natural resources, including the preservation of habitats and wildlife  Today, conservation efforts focus on protecting entire ecosystems as well as single species. Protecting an ecosystem will ensure that the natural habitats and the interactions of many different species are preserved at the same time.

6-4 CHARTING A COURSE FOR THE FUTURE

Many biologists are concerned about the biological effects of two types of global change: the thinning of the ozone layer and global warming

Ozone Depletion  Ozone layer – the concentration of ozone gas that the atmosphere contains between 20 and 50 km above the Earth’s surface  In the 1970s, scientists found evidence that the ozone layer was in trouble. A hole was discovered in the ozone layer. Over the years, the hole has been growing larger. A second has also been found. These holes allow higher than normal levels of UV onto the Earth.  These holes were caused by CFCs, which were used in aerosol cans, Styrofoam, and coolants. The use of CFCs have been phased out.

Global Warming  Global warming – the increase in the average temperature of the biosphere  Over the past 120 years, global temperature have risen 0.5 degrees Celsius.  Temperatures are rising at a faster rate now than they did during the previous 100 years.  Some scientists believe that human activities have caused global warming by adding carbon dioxide (from burning fossil fuels) and other greenhouse gases such as methane to the atmosphere. If global warming continues at its current rate, the polar ice caps will continue to melt and sea levels could rise enough to flood some low-lying coastal areas. Storms and other weather disturbances could become more frequent and more severe.