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E & E Key Concepts
Why E & E?
Why have Environment and Ecology as a topic of study K-12, and why IPM?? First, let's put the topic of Environment and Ecology in perspective.
Understanding the functioning of the environment and ecological principles is fundamental to our long-term survival. Studying environment and ecology is the ultimate applied science because it is completely interdisciplinary and our understanding (or lack thereof) will inform the decisions we make about "managing" earth's resources. These decisions, for better or worse, will determine what kind of world our descendents will inherit.
What is the human "ecological footprint" on the living earth?
In class, you have seen a video entitled "World Population" in which the projected growth of human population was visually charted on a world map by adding white dots for every 1 million people. It is obvious that at our current rate of growth, we will exhaust the resource base upon which we depend and will continue to degrade the environment with our waste unless we act rationally. As thinking human beings, we must ask ourselves, how can we sustain ourselves and our world? This question has to begin with each of us. In the most simple terms, we must ask ourselves:
What are our limits to growth as a population?
How are population growth and consumption related?
What do we consume?
How much do we consume?
What is the ecological cost to produce those things for us under current practices?
What kinds of wastes do we produce?
How much waste do we produce?
What is the ecological cost of our waste production and disposal under current practices?
Take a moment to look at the attachments:
"If the world population was 100 . . ."
"What's your share of the global commons?"
When you can, visit the website:
http://www.footprintnetwork.org/gfn_sub.php?content=footprint_overview to calculate your personal "ecological footprint"
Beyond paying attention to the decisions we make in our individual lives, it is important to gain some understanding of how life on earth functions. What are the key principles at play and how can we both use these principles to our advantage and sustain our ecosystems functioning?
We will consider these factors on the next page.
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If the world population was 100...
If we could shrink the earth's population to a village of precisely 100 people, with all the existing human ratios remaining the same, it would look something like the following.
There would be:
57 Asians
21 Europeans
14 from the Western Hemisphere, both North and South America
8 Africans
52 would be female
48 would be male
70 would be non-Christian
30 would be Christian
89 would be heterosexual
11 would be homosexual
6 people would possess 59% of the entire world's wealth and all 6 would be from the United States.
80 would live in sub-standard housing
70 would be unable to read
50 would suffer from malnutrition
1 would be near death
1 would be near birth
1 (yes, only1) would have a college education
1 would own a computer
"When one considers our world from such a compressed perspective, the need for both acceptance, understanding, and education becomes glaringly apparent."
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What do we know about how ecosystems function?
Key Concepts
Our world functions as a living system only because we have energy flowing and nutrients cycling. Everything is connected via these cycles. Put another way - IT'S ALL ABOUT FOOD!!
1. Energy flows
Here on earth, we have:
a) a constant source of energy (the sun) and
b) organisms that can trap that energy in a useful form (plants - thank a plant today!)
The energy that comes in does not go back. Plants are said to function as primary producers because it all starts with them. They "capture" the sun's energy, and magically by photosynthesis, "fix" carbon from the air (CO2) and make pop-tarts. (Ok, not really, but they do make carbohydrates - where do you think sugar comes from??)
In living organisms, captured chemical energy is transferred each time one organism eats another. Plants are eaten by primary consumers (say, grasshoppers). Secondary consumers (say, sparrows) eat the primary consumers. Tertiary consumers (say, sparrow hawks) eat the secondaries. At each transaction, only a portion of energy is captured; the rest is "lost" as heat. The pyramid of energy symbolizes that as you go up the "food chain", less and less energy is captured by that group. This is why, by weight, there are jillions of pounds of insects and only a few pounds of predatory birds per acre. The higher up on the pyramid you eat, the more energy it took from the layers below to support you. Also, for the same reason, the more precarious your food supply is. Can you see why?
2. Nutrients cycle
All the elements that make up matter on earth (AKA, the periodical chart of elements) are already here. They can get moved around through different drawers in the cabinet of the world (land, air, water, living organisms), but the total amount stays the same. Certain of these elements are defined as "nutrients" because they are the building blocks of life, for example, carbon, nitrogen, potassium, phosphorus, sulfur, etc. and because plants can pick them up and all other biological molecules- proteins, fats, carbohydrates are made in nature by plants. (These molecules made by plants then give Mr. Nabisco (?) the ingredients to make Pop-tarts.)
As we have seen, plants are in turn eaten by everybody else, the consumers. In nature, consumers return these chemicals to the plants by releasing bodily wastes - feces, urine and ultimately death. The final conversion is possible thanks to a series of decomposers who break these larger pieces back down to elemental forms plants and take up. Voila - cycling of nutrients!
3. Everything is connected
Globally, the world's ecosystems function, in a sense, as a series of living machines, all connected through the flow of air and water. So for example, the lichens growing on rocks in the harsh northern tundra still contain radioactive isotopes from nuclear blasts in the tropical South Pacific years ago. Certain elements that form a gas, such as carbon the form of CO2 and nitrogen, cycle globally. Locally, within an ecosystem, other nutrients that move through the soil and water cycle into and out of the living and non-living compartments over and over. These cycles, local or global also carry around with them all the man-made chemicals that do not exist "in nature". That is why there is still DDT in the fat of fish - even though DDT was banned many years ago. In short, when we dump something down the drain or throw something "away" - where is that exactly? There is no "away".
4. Food Webs
Beyond water and air carrying elements and other molecules around, life is connected by who eats whom. In a given ecosystem, the species composition and numbers of the producers, consumers and decomposers form an intricate web. Thus, some species may depend on only one or two others for food. Others may eat just about anything. In stable environment, predator - prey interactions tend to keep the food webs species in balance with each other; no one species "explodes" and pushes the others out. If an environment is disturbed, or new, exotic invasive species move in, the entire food web can be changed, often decreasing the total number of species or biodiversity of the site.
5. Productivity
Productivity in the ecological sense refers to a system's ability to trap energy and convert it to living material - that is, create biomass. Primary productivity is the amount of carbon that is converted into plant biomass in a given amount of time. Different ecosystems have differing rates of productivity. Why? Because different areas of the globe have different amounts of light, temperature (heat), rainfall, soil type, nutrient availability, types of plant communities and food webs. All of these factor into capacity for productivity.
Ecosystems can be disturbed, poisoned or otherwise altered so they are no longer productive - sometimes, they do not go back. An example might be found in an agroecosystem; hot central valley California agriculture. This system uses and reuses so much irrigation water that a high concentration of salt is left on the soil from the evaporation of water. Over time, the accumulation of salt renders the land useless for agricultural production "forever". Is this a sustainable use of this valuable resource?
In addition, a stable, or "mature" ecosystem has a different rate of productivity than one that has been disturbed. There are constantly disturbances in both nature or caused by humans. Forests can be cut down by people or burned down by fire (although these have different consequences related to nutrient cycling - can you see why?)
6. Succession
When a system is restoring itself, it goes though a predictable series of changes, referred to as plant succession. The first stage of succession is characterized by plants that can invade, grow and set seed quickly (high primary productivity). These are mostly annual plants. In agriculture, we have basically used this ecological principle to our advantage.
In a forest ecosystem, secondary stages of succession bring the introduction of biennials, woody shrubs and eventually trees. Finally, if all goes well, the original "climax" community of a forest with a certain species composition is restored. For each ecosystem and each kind of disturbance, these changes are predictable and take calculable amounts of time. However, some disturbances can be so severe that the system never "goes back" to the original state.
The following activity "The Food Cobweb" illustrates some of the concepts discussed in this section.