The Science of Sustainability

The earth system has three primary sources that affect the flow of energy on Earth. They are solar, geothermal, and tidal. The sun (solar) is a powerful source of energy on Earth and life on Earth could not exist without it. Geothermal is the energy from within the earth and includes volcanoes and earthquakes. Tidal movement of the oceans is caused by the orbiting of the moon around the earth.

Energy is defined as the ability to do work. Work is defined as the application of a force over a distance. Energy can be divided into two broad categories: potential and kinetic. Potential energy is stored energy that has the potential to do work, such as the energy stored in a battery or fuel, while kinetic energy is energy in motion, such as waves crashing against a beach. Energy can be transferred from one form to another. Within the broad categories of potential and kinetic energy, energy can come in many different forms, including chemical, nuclear, mechanical, thermal, electrical, solar, and others.

The earth's resources, which man uses to power modern society, are classified as either renewable or nonrenewable. Renewable energy refers to energy, including electricity, generated from sources that will not be depleted if used in a sustainable manner. Although the specific technologies that are considered renewable vary, they are generally considered to include solar, wind, geothermal, biomass, and hydro.

Renewable energy resources provide an alternative to more prevalent means of electrical power generation, including coal, nuclear, natural gas, and oil. These sources of energy are nonrenewable and will be depleted at some point in the future.

Nuclear power involves hazardous, radioactive materials that can cause cancer and death with exposure. A history of infrequent, but damaging, power plant accidents has historically hampered investment in this technology in the United States. A nuclear meltdown occurred in 1979 at the Three Mile Island power plant in Pennsylvania, which resulted in the release of radioactive gasses. In 1986, an explosion at the Chernobyl Nuclear Power Plant in Ukraine released large quantities of nuclear contamination into the atmosphere. And most recently, in 2011, a tidal wave damaged the Fukushima I Nuclear Power Plant resulting in the full meltdown of three nuclear reactors. All of these accidents have come with high economic costs for the damage and subsequent environmental remediation.

An example of how energy is transformed from one form to another can be seen in the operation of a car. It takes work to move a car down a road. The chemical potential energy stored in gasoline is transferred into thermal energy when the gasoline combusts in the car's engine. The thermal energy released in the engine moves pistons in the engine transforming the thermal energy into mechanical energy. Through gears and other mechanical parts on the cars, the mechanical energy in the engine is transferred through the car resulting in the rotation of the tires, which move the car. The potential energy stored in the fuel is transformed into kinetic energy of the moving car.

A common measurement unit of energy is the British thermal unit (BTU). A BTU is the amount of heat energy required to increase the temperature of a pound of water by one degree Fahrenheit. A BTU is approximately equal to the amount of heat given off by burning a kitchen match. As a BTU is a relatively small unit, BTUs are often stated in larger units, therms or MMBTU. Therms or thermal units are equal to one hundred thousand BTUs. MMBTU is equal to one million BTUs. To help provide some context, a typical residential water heater has a heat output rating of about forty thousand BTU per hour. The average commercial boiler in the United States has an output ability of 9.6 MMBTU per hour.

In terms of electricity, the common unit of energy is the kilowatt hour or kWh. However, as the kilowatt hour is a unit of energy, electricity usage can also be expressed in terms of BTUs, with 1 kWh equal to 3412 BTUs. The units for energy used vary by country. For example, in the United States, engine power is related in terms of horsepower (HP) while in other countries it is rated in terms of kilowatts (kW). The 2012 Honda Civic's engine is advertised as 140 HP in the United States and 103 kW in European countries. Both measures indicate the same amount of power.

Biodiversity

Biodiversity is the result of 3.5 billion years of evolution. Biodiversity is an indicator of the health of an ecosystem. Higher degrees of biodiversity imply greater ecosystem health. Biodiversity not only strengthens the overall health of the planet but also provides vital benefits to humans. Biodiversity is important in agriculture as it provides different varieties of plants and animals for human consumption. Biodiversity helps protect other natural resources, including water and soil. A significant portion of medicine is derived directly or indirectly from organic sources. Industry relies on biological inputs, such as timber, paper, and fiber. Biodiversity also provides leisure, cultural, and aesthetic value.

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Plant and animal species have been disappearing at a rate at least fifty times greater than the natural rate, and this rate is predicted to rise as human activities continue to put demands on ecosystems. Based on current trends, an estimated 34,000 plant and 5,200 animal species face extinction. Agriculture biodiversity is under extreme pressure due to modern commercial agriculture, which has focused on a few specific species of plant and many farm animal breeds are at risk of extinction.

While the loss of individual species is of great concern, of even greater concern is the continued degradation and loss of some of the world's richest ecosystems, including forests, wetlands, and coral reefs. These ecosystems are host to some of the greatest biodiversity on Earth and the loss of these ecosystems is the greatest threat to biodiversity.

The loss of biodiversity reduces the productivity of ecosystems. It weakens ecosystems and reduces their ability to be resilient to extreme natural events, such as floods, droughts, and human activity stresses. While the loss of species has always occurred as a natural phenomenon, the pace of extinction has accelerated dramatically as a result of human activity. This loss of life not only reduces the ecosystems goods and services available to the current generation of humans but also harms future generations as well.

Water

Water covers more than 70 percent of the earth's surface and is vital to all forms of life. Oceans hold 97 percent of surface waters, glaciers, and the ice caps hold 2.4 percent, with lakes, rivers, and other land surface waters making up the remaining 0.6 percent. Water is a vital resource to humans as it is required as drinking water; it is an essential input for agriculture; and it provides for sanitation, transportation, energy generation, food processing, and power generation (through hydroelectric plants or dams). Increases in population and current water use practices are expected to increase water consumption in food production by up to 90 percent.

Currently, one in six people in the world lack safe drinking water, and water-related illness is the leading cause of human sickness and death. In 1989, there were 9,000 cubic meters of freshwater per capita available for human use. By 2000, this had dropped to 7,800 cubic meters, and it is expected to continue to decrease as human population increases. Global per capita figures on water availability are somewhat misleading as the world's available freshwater supply is not distributed evenly geographically, seasonally, or annually. Water distribution is dependent on Earth's hydrological cycle. The movement of water is part of a natural cycle of evaporation into the atmosphere, precipitation, and then runoff across the land and into streams, rivers, and lakes. This cycle is powered by the sun, which serves to move clean water about the planet.

Soil

Soil consists of layers of minerals that vary in characteristics across different geographic regions and ecosystems. Soil consists of both organic and inorganic components. Soil is a primary nutrient base for plants and therefore is important to humans for agriculture. Without soil, the earth would not support a rich base of plant and animal life, and it is an essential resource to consider in human interactions with the environment.