ENVIRONMENTAL AWARENESS; KNOWING YOUR WORLD

GLOBAL WARMING NATURE'S RESPONSE.

Scientists have shown that the Earth's average temperature has risen slightly in the last few decades. But, not all scientists agree on what changes this will bring in Earth's climate.

The Earth has gone through many cycles of warming and cooling in the past. As Earth's climate changes, nature responds to bring things back into balance. We know there has been an increase of carbon dioxide in the atmosphere during the last 100 years. We also know that carbon dioxide absorbs heat from the Earth's surface, slowing the escape of heat from the Earth's surface to space. This is the Greenhouse Effect. This increase in carbon dioxide (CO2) has been partially linked to human activities, such as manufacturing and burning large areas of forest. Some scientists think this will cause the Earth's ice caps to begin to melt, causing ocean levels to rise. Coastal cities would risk flooding. Other scientists think the Earth will adapt. One thought is that some plants will benefit from more carbon dioxide. Since plants use carbon dioxide, this may make them more efficient growers. Some evidence of this may already be occurring in some types of ocean algae. When the algae die, it sinks to the ocean floor, taking carbon with it. This is called carbon sequestration, and is a way the amount of carbon dioxide in the atmosphere might be reduced. Another adaptation that may happen is a change in the Earth's cloud cover. A warmer climate may increase water evaporation. More water vapor in the atmosphere could increase cloud cover. Sunlight would be directly reflected out into space before it reaches the Earth's surface, making less available to heat the Earth. If these adaptations occur, a change in Earth's climate would still take place, but the change may not be as drastic as some predict. It usually takes decades or centuries for changes in climate to take place. We will not know the total effect of the warming atmosphere on Earth's climate and ecosystems for some time. This does not mean that attempts should not be made to reduce the amount of carbon dioxide people are putting into the air. Recently, many governments worldwide met to set up limitations on the amount of carbon dioxide and other greenhouse gases (gases that slow down heat escaping from the Earth). Individuals can do their part by doing things like planting trees and using products that do not release large amounts of carbon dioxide into the atmosphere.

ENERGY AND ECOSYSTEM ; USE SOME LOOSE SOME

Life on Earth is possible because energy flows one way through ecosystems, while matter cycles endlessly. Water and elements, such as carbon, nitrogen, phosphorous, and sulfur are examples of matter that cycles through ecosystems.

The original source of almost all energy in an ecosystem is the Sun. All of the energy the sun releases does not reach Earth. One one-billionth of the Sun's total energy output actually reaches the Earth. Of all the energy that does reach Earth, slightly less than 34 percent is reflected back to space by clouds. The Earth itself reflects another 66 percent back to space. Less than one percent of the total energy that reaches Earth is used by plants for photosynthesis. Plants are often called producers because of their ability to make their own food from the sun's energy. When scientists discuss energy, they often refer to the Laws of Thermodynamics. The First Law of Thermodynamics states that energy can neither be created or destroyed. The Second Law states that energy is constantly converted from high quality to low quality. High quality energy is capable of performing a large amount of work, while low quality energy is capable of performing less work. Scientists know that energy always changes from high to low quality when work is performed. During the change, some energy is lost in the form of heat, which cannot do work. The amount of energy lost as heat is often as high as 90 percent of the total energy involved. Putting all this together in an example, if 1,000,000 units of solar energy were to reach Earth, one percent or 10,000 units, would be available for plants to use. Of these 10,000 units, plants would lose 90 percent, or 9,000 units, as heat. If an animal then ate the plants, it would only receive 1,000 units of energy. These animals are called primary consumers because they cannot produce their own food. Cows and sheep are examples of primary consumers. If another animal eats the cow or sheep, it would only receive 100 units of energy, since the cow or sheep would lose 900 units as heat. Animals that eat other animals are called secondary consumers. Scientists believe that four or five of these energy transformations are the most possible before the amount of energy transferred is too small to support life. NATURAL RESOURCES . CAN WE USE THEM FOREVER???? People use many of the Earth's natural resources. All of the products we use have a natural resource base. Minerals, forest products, water, and soil are just a few of the natural resources humans use to produce energy and make things people use. Some natural resources can be reproduced within a few years or decades. These are called renewable resources. Trees are an example of a renewable resource. Oil, minerals, and soil take hundreds, thousands and even millions of years to be made. These are called non-renewable resources. It is very important we use renewable and non-renewable resources wisely. If a resource is used and thrown away, eventually the resource becomes scarce. When the supply dwindles, its price will increase. Products that are made from that resource would increase in price too. Sometimes resources become so rare they can no longer be used. In these cases, substitute resources may be used, which may make a poorer quality product, or one that is more expensive. If substitutes can not be used, some products could no longer be made. Wise use of resources includes not throwing away products that are reuseable or recyclable. When these products are reused or recycled, it maintains resource availability, uses less landfill space, and uses less energy.