CK-12 Biology I - Honors
Page 84
ecosystem diversity
The variety of ecosystems on Earth.
ecosystem services
Indirect benefits provided by ecosystem processes, such as nutrient cycling and waste disposal.
ecosystem
A functional unit comprised of living things interacting with their nonliving environment.
endemic
A unique species found only within a certain area and nowhere else.
epiphyte
Plant which grows on top of another plant.
exotic (alien) species
A species introduced either intentionally or unintentionally to a completely new ecosystem – a non-native species.
extirpation
Elimination of a species from a particular region of its range.
genetic diversity
Variation among individuals and populations within a species.
genetic pollution
Hybridization or mixing of genes of a wild population with a domestic or feral population.
global warming
The recent increase in the Earth’s average near-surface and ocean temperatures.
greenhouse effect
The trapping by the atmosphere of heat energy radiated from the Earth’s surface.
keystone species
Species having a functional importance to ecosystem diversity and stability which far outweighs its numerical or mass importance.
monoculture
Large-scale cultivation of single varieties of single species.
natural resource
Something supplied by nature which supports life, including sources.
pollution
Release into the environment of chemicals, noise, heat or even light beyond the capacity of the environment to absorb them without harmful effects on life.
salination
Increase in salt levels in soils.
species diversity
The number of different species in an ecosystem or on Earth.
sustainable forest management
Forest management which ensures that the goods and services yielded from a forest remain at a level that does not degrade the environment or the potential for similar levels of goods and services in the future.
sustainable use
Use of resources at a rate which meets the needs of the present without impairing the ability of future generations to meet their needs.
Points to Consider
Most of this lesson considered species and ecosystem diversity. Why is genetic diversity also very important?
How does biodiversity in your area compare to the general global pattern of biodiversity? Give some reasons why it may or may not follow general trends.
Choose one other area in which you are interested, and make the same comparison.
Do you find the extinction statistics presented in this lesson alarming? Why do you think we don’t hear more about the Sixth Extinction and the predicted loss of biodiversity?
Which values of biodiversity do you feel are most compelling?
Which solutions will you adopt in your daily life?
Lesson 18.2: Natural Resources
Lesson Objectives
Distinguish between renewable and non-renewable resources.
List the major energy and material resources upon which humans depend.
Discuss the stresses increasing human consumption places on resource renewal.
Sequence the events which lead to the formation of fossil fuels.
Assess levels of depletion of non-renewable energy resources.
Analyze the ways in which technology and consumption result in overharvesting, pollution, atmospheric changes, and habitat loss.
Evaluate the effects of population growth on resource use and environmental pollution.
Relate inequalities in resource distribution to global political stability.
Compare the concept of sustainable use to that of renewable vs. nonrenewable resources.
Describe the nature and uses of soil resources.
Describe how human activities including technology affect ecosystem services such as
Soil generation
Waste disposal
Nutrient cycling
Recycling dead organic materials
Fertility of the land
Discuss effects of population growth, technology, and consumption on land and soil resources.
Relate soil erosion, pollution, and land development to ecosystem stability.
Connect soil erosion, pollution, and land development to global stability.
Evaluate the effects of changes in these services for humans.
Review conflicts between agricultural technology, environment, and society.
Recognize tradeoffs required by nuclear power plants: reduced emissions vs. radioactive fuels and waste.
Analyze the ways in which humans have altered soil and land resources for other species.
Identify the extent of terrestrial ecosystem loss, and its effects on biodiversity.
Interpret the effects of soil pollution on biodiversity.
Describe how human activities including technology affect ecosystem services such as:
The hydrologic cycle
Waste disposal
Nutrient cycling
Evaluate the effects of changes in these services for humans.
Discuss the effects of population growth, technology, and consumption on water resources.
Explain the effects of overdrafting, pollution, and atmospheric changes on ecosystem stability.
Relate overdrafting and pollution to global stability.
Analyze the ways in which humans have altered water resources for other species.
Identify the extent of wetland loss, and its effects on biodiversity.
Interpret the effects of water pollution on biodiversity.
Introduction
Defining natural resources raises important philosophical questions.
“Resources” are useful or valuable. But are resources useful for and valuable to humans – or all life? If we “use” them, do we necessarily “consume” them? Is value limited to economics? Are resources limited to materials, or can they include processes, systems, and living things?
Definitions of “natural” go straight to the heart of our views about ourselves. Most definitions include a tension or conflict between the human and the non-human parts of the Earth: Anything that is natural is “not altered or disguised,” “not produced or changed artificially,” or, rather unhelpfully, “found in nature.” We often define nature as separate from humans: “the world of living things and the outdoors” or with elements of inner conflict (“a primitive state of existence, untouched and uninfluenced by civilization or artificiality”) or even religion (“humankind’s natural state as distinguished from the state of grace”).
It is not an idle exercise to think carefully about your own definition of natural resources, because such thinking can clarify your relationship and responsibilities to the Earth. Do natural resources exist only for humans to use (or “exploit” – a term repeated in many definitions)? Are we apart from nature, or a part of nature? In what ways are we similar to other species? How are we different? How do those similarities and differences help us to define our responsibilities to “nature” – to other species and our physical environment?
Historically, the concept of natural resources was intended as a measure of respect and appreciation for the materials Earth provided, and the supplies humans used and modified to develop the civilization in which they lived. Economic value was primary, and a list of natural resources would include energy sources such as coal or oil and raw materials such as iron or copper. Living things could be, but often were not added: fibers from plants, and skins from animals.
As use became exploitation and later depletion, we began to better appreciate our dependence on natural resources, as well as our power over them. Economist E.F. Schumacher, in a 1973 series of essays t
itled Small is Beautiful, suggested that our economy is unsustainable because natural resources (especially energy) can be depleted. He made the case that natural resources should be considered capital, rather than expendable – conserved, rather than simply used. He also argued that nature’s capacity to resist pollution is limited, pointing to the value of whole ecosystems and ecosystem services. During the 1990s, ecological economist Robert Constanza calculated that “nature’s services” were worth $33 trillion per year – more than the $25 trillion total of the inter-human economy at that time. Although awareness of resource depletion and ecosystem services is increasing, their values remain inadequately recognized by our economy, and sustainability remains a goal for the future.
What definition for natural resources shall we use? On the Department of Energy’s “Ask a Scientist” website, Bob Hartwell defines a natural resource as “something supplied by nature which supports life on this planet.” This concise description includes most of the ideas we’ve discussed above, and views human use with an ecological perspective appropriate for the study of biology. Humankind is a part of nature, one species in an interdependent web which includes the Earth and all life. Without question, we are a unique species: we have the power to change that interdependent web in ways no other species can, we have the ability to learn about and understand the patterns and processes which maintain the web, and we have the responsibility to use our natural resources together with that understanding in ways which sustain the web – for our ourselves and for all life.
Most biologists today would probably classify ecosystems, their processes and “services,” and their species as natural resources, together with energy sources and materials from the environment. Biodiversity (which includes both species and ecosystems) is certainly a natural resource, according to this definition. In this sense, this entire chapter explores natural resources. The first lesson dealt with biodiversity as well as some of the ecosystem services which depend on biodiversity. This lesson will focus on energy, land and soil, and water resources. Because several unique problems (acid rain and ozone depletion, for example) apply to atmospheric resources, we will focus on the atmosphere in a third lesson. A final lesson will combine our concerns about the closely related issues of energy use and atmospheric change to focus on climate change. These lessons will by no means address all natural resources, but they should give you an overview of the complexities of and need for sustainable use, and provide you with some detailed insight into several major problems.
Renewable and Nonrenewable Resources: Energy and Sustainable Use
Applied to natural resources, renewable or non-renewable are relative rather than precise terms. Not surprisingly, we use human parameters to classify resources into these two categories.
Figure 18.22
Solar radiation and wind energy are considered renewable resources because their availability far exceeds our rates of consumption. Here, availability is shown as volume equal to the annual flux in terawatts (1 TW = 10 watts). Eighty-nine thousand TW represents the amount of sunlight that falls on the Earth's surface, 370 TW depicts all the energy in the wind, and 15 TW was the global rate of energy consumption in 2004.
A resource replenished by natural processes at a rate roughly equal to the rate at which humans consume it is a renewable resource. Sunlight and wind, for example, are in no danger of being used in excess of their longterm availability (Figures above, below). Hydropower is renewed by the Earth’s hydrologic cycle. Water has also been considered renewable, but overpumping of groundwater is depleting aquifers, and pollution threatens the use of many water resources, showing that the consequences of resource use are not always simple depletion. Soils are often considered renewable, but erosion and depletion of minerals proves otherwise. Living things (forests and fish, for example) are considered renewable because they can reproduce to replace individuals lost to human consumption. This is true only up to a point, however; overexploitation can lead to extinction, and overharvesting can remove nutrients so that soil fertility does not allow forest renewal. Energy resources derived from living things, such as ethanol, plant oils, and methane, are considered renewable, although their costs to the environment are not always adequately considered. Renewable materials would include sustainably harvested wood, cork, and bamboo as well as sustainably harvested crops. Metals and other minerals are sometimes considered renewable because they are not destroyed when they are used, and can be recycled.
Figure 18.23
Wind power is considered a renewable resource because the rate of supply far exceeds the rate of use ( ). Although current use supplies less than 1% of the worlds energy needs, growth in harvesting wind energy is rapid, with recent annual increases of more than 30 percent.
A non-renewable resource is not regenerated or restored on a time scale comparative to its consumption. Non-renewable resources exist in fixed amounts (at least relative to our time frame), and can be used up. The classic examples are fossil fuels such as petroleum, coal, and natural gas. Fossil fuels have formed from remains of plants (for coal) and phyto- and zoo-plankton (for oil) over periods from 50 to 350 million years. Ecologist Jeff Dukes estimates that 20 metric tons of phytoplankton produce 1 liter of gasoline! We have been consuming fossil fuels for less than 200 years, yet even the most optimistic estimates suggest that remaining reserves can supply our needs for
Coal: 252 years.
Gas: 72 years
Oil: 45 years
Nuclear power is considered a non-renewable resource because uranium fuel supplies are finite. Some estimates suggest that known economically feasible supplies could last 70 years at current rates of use - although known, and probably unknown reserves are much larger, and new technologies could make some reserves more useful.
Figure 18.24
Global energy use includes mostly non-renewable (oil, coal, gas, and nuclear) but increasing amounts of renewable (biomass, hydro, solar, wind, geothermal, biofuels, and solar photovoltaic) resources.
Recall that the Second Law of Thermodynamics (which states that the entropy of an isolated system which is not in equilibrium will tend to increase over time) reinforces this view of “renewable” and “non-renewable” resources: Energy flows downhill – gets used up, is transformed into heat; only materials that can be recycled are “renewable.” It is only our time scale which makes any form of energy renewable. Eventually, the sun will burn out, as well.
Population growth, industrialization of developing countries, and advances in technology are placing increasing pressures on our rates of consumption of natural resources. Pollution and overexploitation foreshadow resource depletion, habitat loss, and atmospheric change. Unequal distribution of wealth, technology, and energy use (Figure below) suggest that developing nations will further increase demands on natural resources. With these increases in demand, current levels of resource use cannot be maintained into the future, and social and political instability may increase. Improvements in technology could mitigate these problems to some extent.
Figure 18.25
Per capita energy consumption illustrates the unequal distribution of wealth and natural resource use which threatens long-term resource supplies as developing nations demand higher standards of living. These inequalities threaten not only resource supplies but also global political stability.
The concept of renewable vs. non-renewable resources clearly depends on rates of human use (Figure above); less clearly, its usefulness depends on the effects of use on other natural resources, such as pollution. Of course, we could change our rates of consumption. Indeed, if we increase our rate of consumption, renewable resources may need to be reclassified as non-renewable. This is the foundation of the concept of sustainable use – use of resources at a rate which meets the needs of the present without impairing the ability of future generations to meet their needs. Notice that this concept continues to focus on human needs; however, a solid understanding of ecology recognizes that human needs depend on entire eco
systems, which in turn depend on all species. Sustainable use could also apply to ecosystem services, which can be overwhelmed by overuse even though their “use” does not involve consumption. Perhaps we should shift our natural resource focus from rate of consumption (renewable vs. non-renewable) to sustainable use!
Soil and Land Resources
What negative connotations we give to soil resources in our daily conversation! Hands are “dirty;” clothing is “soiled.” Yet the formation of soils require thousands and even millions of years of physical, geological, chemical, and biological processes. Soil’s complex mixture of eroded rock, minerals, ions, partially decomposed organic material, water, air, roots, fungi, animals, and microorganisms supports the growth of plants, which are the foundation of terrestrial ecosystems (Figure below). Soil is a balanced intersection of air, water, and land resources, sensitive to changes in any one element. We use soils for agriculture, gardening, landscaping, earth sheltered buildings, and to absorb waste from composting and septic drain fields. Peat, an accumulation of partially decayed plant material, can be burned for energy.
Figure 18.26
Soil resources are a complex mixture of eroded rock, minerals, ions, partially decomposed organic material, water, air, roots, fungi, animals, and microorganisms, formed over thousands or even millions of years.
Soils can assimilate and remove low levels of contamination, thus it is useful for waste treatment. Not surprisingly, high levels of contamination can kill soil microorganisms, which help to accomplish this service. Toxics from industry, underground storage tanks, pesticide use, and leaching from landfills and septic tanks contaminate soils across the globe. Contaminated soils endanger human and ecosystem health.