drought occurred in the region during the 1950’s, the mid-1970’s, and the late 1980’s. More vegetative cover on the land, federal crop insurance, and more knowl- edgeable farmers resulted in fewer dust storms, less erosion, and less financial strain on farmers. David M. Diggs See also: Civilian Conservation Corps; Desertifica- tion; Drought; Erosion and erosion control; Natural Resources Conservation Service; Soil management; Weather and resources. Dynamite Category: Obtaining and using resources The invention of dynamite has had an effect on the procuring of coal, silver, gold, and any other materials which are mined by tunneling. Definition Many different formulations are called dynamite, but all are stabilized forms of nitroglycerine. Dynamite is an explosive that is highly dense so that a large explo- sive power is available from a small volume of mate- rial. Overview Explosives have been a part of underground mining ever since their discovery. Until the mid-1800’s the only explosive available was black powder, which was lacking in power and created flames that constituted a fire or dust explosion hazard in mines. Nitroglycerine was discovered by an Italian chemist, Ascanio So- brero, in 1847. It is an oily organic liquid that is a highly powerful explosive—and an extremely unsta- ble chemical. Temperature increases or mechanical shock readily detonate nitroglycerine. Although it did find use in the mining industry, the hazard of pre- mature explosions was extreme, and the industry searched for an alternative. The material known as dynamite was discovered by Swedish inventor Alfred Nobel in 1867. After several years of experiments aimed at stabilizing nitroglycer- ine, Nobel found that when the liquid was absorbed by diatomaceous earth the mixture was safe to handle and did not explode unless a blasting cap was used to initiate the reaction. Nobel went on to commercialize the production of dynamite by building manufactur- ing facilities on a worldwide basis and thereby accu- mulating a large fortune. Upon Nobel’s death, his will left a considerable portion of his fortune to establish the Nobel Prizes. Modern dynamite is a dry granular material that is fundamentally stabilized nitroglycerine. It finds its greatest application in underground mining, where its high explosive power per volume is a desired qual- ity. Other chemicals are mixed with the basic ingredi- ents to improve certain aspects of its performance. Some particular formulations are designed to reduce the level of carbon monoxide and nitrogen dioxide that are produced in the explosion so that they do not create a hazard for miners. Another form is of particu- lar use when high explosive power is needed at low op- erating temperatures. When packaged for use, the solid is packed into pa- per cylinders ranging from 2 to 20 centimeters in di- ameter and from 20 to 100 centimeters in length. These sticks are placed in boreholes in the mine face, tamped into place, and fitted with an electrical deto- nator. In coal mining a dynamite form that produces a slow shock wave is used so that the pieces of coal dis- lodged are relatively large. For other deep mining purposes a form producing a fast shock wave is used to fragment the rock more thoroughly into smaller rock pieces that can be more easily processed. Dynamite also finds a role in strip mining or pit mining, where its highly dense explosive power is not needed. In these instances, it is used as a primer to detonate other, lower-cost, blasting agents. Kenneth H. Brown See also: Coal; Diatomite; Quarrying; Strip mining; Underground mining. 320 • Dynamite Global Resources E Earth First! Category: Organizations, agencies, and programs Date: Established 1979 Earth First! comprises a group of activists from around the world who employ radical, sometimes illegal tactics to oppose environmental exploitation and are dedi- cated to defending “Mother Earth.” The movement is a network of autonomous groups with no central office, paid officers, or decision-making boards. Members are motivated by a belief in biocentrism or deep ecology. Background Earth First! was founded in the United States by Da- vid Foreman. Calling itself a movement rather than an organization, it is active in several countries. Its tools include grassroots organizing, litigation, civil disobedience, and “monkeywrenching.” Earth First! activists criticize the corporate structures and image- consciousness of many environmental groups. They are committed to saving the wilderness and use the slogan, “No compromise in the defense of Mother Earth.” Earth First! activists have adopted a variety of mili- tant tactics, including drilling steel spikes into trees (to make it impossible to cut them with mechanized saws), adding sugar to the fuel tanks of bulldozers, and chaining themselves to tree crushers. The orga- nization also uses theatrical demonstrations to keep the public aware of environmental issues. The Earth First! journal, published six times per year, chroni- cles the activities of the radical environmental move- ment. Impact on Resource Use One of Earth First!’s visions for the future is the devel- opment of a 290-million-hectare wilderness system. In this area, priority would be given to the preservation of indigenous species and ecosystems. Stringent guidelines would mandate no human habitation ex- cept for those indigenous to the area and living a tra- ditional lifestyle; no mechanized equipment; no roads, buildings, or power lines; no logging, mining, industry, agricultural development, or livestock graz - ing; and the reintroduction of indigenous species and removal of all species not native to the area. Marian A. L. Miller Web Site Earth First! Earth First! Worldwide http://www.earthfirst.org/ See also: Environmental movement; Friends of the Earth International; Greenpeace; Sea Shepherd Con- servation Society. Earth Summit Categories: Laws and conventions; historical events and movements Date: June 3-14, 1992 The United Nations Conference on Environment and Development in Rio de Janeiro, Brazil, also known as the Earth Summit, focused on the environment and sustainable development. Delegates from participating countries signed several documents—including Agenda 21, the Rio Declaration on Environment and Development, the Statement of Forest Principles, the United Nations Framework Convention on Climate Change, and the United Nations Convention on Bio- logical Diversity—regarding the management of global resources. Background In the 1960’s, the issue of environmental protection was gaining prominence in the United States and in other developed countries. As part of this political climate, the United Nations held the 1972 U.N. Con- ference on the Human Environment in Stockholm, Sweden. At the conference, 114 countries adopted a declaration on the management of global resources. The United Nations Environment Programme was created after the conference to facilitate coordinated international action. In the 1970’s and 1980’s, global environmental problems such as overpopulation, over- consumption, ozone depletion, and transboundary air pollution increased. These problems were con- nected to other issues in world politics, including globalization, the liberalization of world trade, rela- tions between developed and developing countries, and international resource production and use. This resulted in the creation of the World Commission on Environment and Development in 1983, chaired by former prime minister of Norway, Gro Harlem Brundtland, to develop an international strategy to address global environmental and resource problems. The Brundtland Commission’s efforts resulted in the 1987 report Our Common Future, which established the discourse of sustainable development. The report led the United Nations to organize the Earth Summit in 1992. Provisions Delegates from participating countries signed several global provisions, such as Agenda 21, at the Earth Summit. Agenda 21 is a nonbinding plan of action to pursue international sustainable development, ad- dressing specific environmental issues and domestic policies. The Rio Declaration on Environment and Development is a nonbinding set of twenty-seven principles to direct sustainable development efforts throughout the world. Its main concern is sustainable development, but it recognizes the importance of healthy, functioning ecosystems. The Statement of Forest Principles, another nonbinding statement adopted at the Earth Summit, pertains to the manage- ment of global forest resources and indicates a recog- nition of the differential obligations of developed and developing countries for the protection of the envi- ronment. Also, signed at the Earth Summit was the United Nations Framework Convention on Climate Change, an international treaty to address the issue of global greenhouse-gas emissions. Also signed was the United Nations Convention on Biological Diversity, the first treaty to address the issue and importance of the preservation of biodiversity through the protec - 322 • Earth Summit Global Resources Brazilian president Fernando Collor de Mello signs the United Nations Convention on Climate Change at the 1992 Earth Summit, while U.N. secretary general Boutros Boutros-Ghali, right, and other diplomats applaud. (AP/Wide World Photos) tion of ecosystems rather than through the protection of independent species. Impact on Resource Use The impact of the Earth Summit is related mainly to the documents discussed above. Agenda 21 im- pacted resource use by providing recommendations for specific resource management policies, including a call for the repeal of subsidies incongruent with sustainable development. It also requires countries to include environmental factors in their statistical ac- counting. The United Nations Framework Conven- tion on Climate Change did not in itself establish lim- its to greenhouse-gas emissions, but it required the subsequent adoption of limits like those in the 1997 Kyoto Protocol. The Convention on Biological Diver- sity led to the subsequent adoption of the Cartagena Protocol on Biosafety, which allows for the regulation of genetically modified organisms. Katrina Taylor See also: Agenda 21; Biodiversity; Greenhouse gases and global climate change; Kyoto Protocol; United Nations climate change conferences; United Nations Environment Programme; United Nations Frame- work Convention on Climate Change. Earthquakes Category: Geological processes and formations Earthquakes result from fractures within the Earth which are produced by a buildup of stress in brittle rock. When the frictional forces holding blocks of rock together are overcome, the Earth moves and produces cracks which can infill with minerals. Definition Earthquakes occur following the rapid release of en- ergy stored in rocks. Rocks beneath the Earth’s sur- face are continually subjected to forces in all direc- tions. When the forces exceed the limits which the rocks can sustain, they respond by either folding or breaking. If the forces are relatively rapid and the rocks are brittle, then the rocks actually break. The result is a shaking of the ground. This shaking is most prominent on the Earth’s surface. Overview An earthquake first originates at a point called the fo- cus, which is beneath the Earth’s surface. This frac- ture, which begins at a point, grows from a micro- scopic crack into a large fault which can extend for many kilometers. However, as mentioned, this frac- ture will be propagated only through brittle material. In other words, faults will not extend indefinitely into the Earth’s subsurface. Nor will they extend indefi- nitely through brittle material, because there will be a point where there is insufficient energy remaining to break rock far removed from the initial source of a fracture. Focal depths of earthquakes occur over a range of depths, extending from just below the Earth’s surface to a depth of approximately 700 kilo- meters. Below this great depth rocks are no longer brittle and thus cannot break. In addition to the more obvious effects of seismic activity on the surface, earthquakes cause a consider- able amount of subsurface activity. Seismic energy passing through brittle rock produces faults and cracks of varying sizes throughout the rock. These fis- sures serve as conduits for fluids, which can move through the rock much more readily than they could before the rock was broken. If the fluids contain dis- solved minerals, these will be deposited in concen- trated amounts. Such is the case when molten rock rises below the surface and is injected into cracks. Concentrated deposits of gold, silver, and other valu- able metals are commonly found filling cracks that were produced by earthquakes that occurred in the recent geologic past. Large-scale faulting can move massive blocks of rock closer to the Earth’s surface. If these blocks are later exposed by erosion of the overlying material, new minerals are exposed. Layers containing coal, limestone, and gravels become available for mining. David M. Best See also: Lithosphere; Pegmatites; Plate tectonics; Seismographic technology andresource exploitation. Global Resources Earthquakes • 323 Earth’s crust Category: Geological processes and formations The earth’s crust is the outer hard layer of the planet. The crust overlies the Earth’s mantle and is separated from it by the Mohorovi5i5 discontinuity, or Moho. There are two great classes of crust on Earth, oceanic and continental, which differ in thickness, composi- tion, density, age, mode of formation, and significance for mineral resources. Background The earth consists of a nested set of spheres of differ- ent composition and of decreasing density with dis- tance from the center of the Earth. The crust is the outermost and lowest-density hard shell, significantly less dense (2.7 to 3.0 grams per cubic centimeter) than the underlying mantle (3.3 grams per cubic centimeter). The earth’s two distinct types of crust— continental and oceanic—differ in five fundamental aspects: thickness, density, composition, age, and mode of formation. Continental and Oceanic Crust Continental crust is generally found beneath the ex- posed parts of the Earth’s surface known as conti- nents. In addition, continental crust is submerged and makes up the continental shelves and submerged continental platforms. Correspondingly, a larger pro- portion of the Earth’s surface is composed of conti- nental crust (40 percent) than is exposed above sea level as continents (25 percent). Oceanic crust makes up the floor of the oceans; in rare cases it rises above sea level, such as in Iceland and Ethiopia. Our store of nonrenewable natural resources is produced and kept in the crust. Hydrothermal systems associated with oceanic crust formation at mid-ocean ridges pro- duce metal deposits. Nearly all economic ore deposits are extracted from the continental crust. Basins in the continental crust and along the continental margins are the principal sites for the formation and storage of oil and gas deposits. Typical continental crust is about 40 kilometers thick, has a density of about 2.7 grams per cubic centi- meter, and has a bulk compositionsimilartothevolca- nic rock andesite; it is about 60 percent silicon diox- ide (SiO 2 ). Continental crust as old as 4 billion years has been found, and 2.5 billion-year-old continen- tal crust is common. The earth is about 4.5 billion years old, and continental crust from the Earth’s first 500 million years has not been preserved. This con- trasts with the situation for Earth’s moon, where the lunar highlands preserve crust that formed shortly after the moon itself. Oceanic crust is about 6 kilo- meters thick, has a density of about 3.0 grams per cu- bic centimeter, and has a bulk composition similar to the volcanic rock basalt (about 50 percent SiO 2 ). Al- though ophiolites may be much older, the oldest in situ oceanic crust is about 170 million years old. The large difference in age between oceanic and continental crust reflects the greater density of the former, which allows it to slide back into the mantle along subduction zones. In contrast, buoyant conti- nental crust is difficult to subduct. The formation of oceanic and continental crusts is fundamentally different as well: Oceanic crust forms by sea- floor spreading at mid-ocean ridges, whereas continental crust forms at island arcs lying above subduction zones (such as Japan or the Mariana Islands in the western Pacific). Although the area of oceanic crust is much larger than that of continental crust (60 percent versus 40 percent of the Earth’s surface), the volume of continen- tal crust is much larger than that of oceanic crust (80 percent versus 20 percent). Metal and Hydrocarbon Deposits The two types of crust play different roles in the formation of nonrenewable natural resources such as metallic ores and hydrocarbons. Metal - lic ores are predominantly produced at diver - 324 • Earth’s crust Global Resources Chemical Composition of Earth’s Crust Element Weight (%) Volume (%) Oxygen (O) 46.59 94.24 Silicon (Si) 27.72 0.51 Aluminum (Al) 8.13 0.44 Iron (Fe) 5.01 0.37 Calcium (Ca) 3.63 1.04 Sodium (Na) 2.85 1.21 Potassium (K) 2.60 1.88 Magnesium (Mg) 2.09 0.28 Titanium (Ti) 0.62 0.03 Hydrogen (H) 0.14 — gent or convergent plate boundaries—that is, where oceanic crust is either produced or destroyed. Vast de - posits of manganese and cobalt exist on the deep-sea floor in the form of manganese nodules. Hydrocar - bon deposits form principally in basins on continen- tal crust or beneath continental margins, at the boundary between oceanic and continental crust. The configuration of continents may also be impor - Global Resources Earth’s crust • 325 50 40 30 20 10 0 Kilometers below surface Kilometers below sea floor 10 8 6 4 2 0 Peridotite (Mantle) Gabbro Basalt Sediments Water Peridotite (Mantle) Granulite Granodiorite Upper crust Lower crust Moho Moho Precambrian rock Conrad discontinuity Oceanic Crust Continental Crust Comparison of Oceanic and Continental Crust tant for controllingoilandgasdeposits,becauseitcan cause the formation of restricted basins where oxy- gen-poor waters allow organic matter to be preserved and buried. The relatively thin sedimentary se- quences typically deposited on oceanic crust are not conducive to formation and preservation ofhydrocar- bon deposits. The distribution of mineral and hydrocarbon re- sources is strongly controlled by the age of the crust and the sedimentary basins that these harbor. In spite of the fact that the oceanic crust is the principal factory for generating ore deposits, a minuscule proportion of these are presently exploited, largely for economic rea- sons. Because of its age and mode of formation, the continental crust acts as a warehouse for ore deposits produced over Earth’s history, especially those depos- its produced at convergent plate boundaries. Particu- larly rich ores are preserved in crust produced in the first 2 billion years of Earth history, and those nations which have large tracts of such ancient crust (among them are Australia, Canada, Russia, and South Africa) are blessed with especially rich metal deposits. Resource Frontiers A wide range of mineral and hydrocarbon resources are sought on all continents except Antarctica. This search benefits increasingly from abundant techno- logical resources, including satellite remote sensing, geophysical surveys, geochemical studies, and tradi- tional field mapping, and from the tremendous in- crease in computing power available to process large and complex data sets. These nonrenewable resources are likely to be depleted in the future, leading to a rise in prices that will reward exploitation of “frontier” de- posits. Resource frontiers pertaining to the Earth’s crust include mining and drilling for oil deeper below the continental surface, drilling for oil in deeper water offshore, the mining of deep-sea resources, and exploiting geothermal and hydrothermal resources for energy, including the tremendous heat energy stored in the deep continental crust and vented from hydrothermal sites along the midocean ridges. Robert J. Stern Further Reading Brown, Michael, and Tracy Rushmer, eds. Evolution and Differentiation of the Continental Crust. New York: Cambridge University Press, 2006. Condie, Kent C. Earth as an Evolving Planetary System. Boston: Elsevier Academic Press, 2005. Davis, Earl E., and Harry Elderfield, eds. Hydrogeology of the Ocean Lithosphere. New York: Cambridge Uni- versity Press, 2004. Fowler, C. M. R. The Solid Earth: An Introduction to Global Geophysics. 2d ed. New York: Cambridge Uni- versity Press, 2005. Grotzinger, John P., et al. Understanding Earth. 5th ed. New York: W. H. Freeman, 2007. Mathez, Edmond A., and James D. Webster. The Earth Machine: The Science of a Dynamic Planet. New York: Columbia University Press, 2004. Rogers, John J. W., and M. Santosh. Continents and Supercontinents. New York: Oxford University Press, 2004. Taylor, Stuart Ross, and Scott M. McLennan. The Con- tinental Crust: Its Composition and Evolution, anExam- ination of the Geochemical Record Preserved in Sedimen- tary Rocks. Boston: Blackwell Scientific, 1985. Web Site U.S. Geological Survey The Earth’s Crust http://earthquake.usgs.gov/research/structure/ crust/index.php See also: Deep drilling projects; Geothermal and hy- drothermal energy; Hydrothermal solutions and min- eralization; Igneous processes, rocks, and mineral de- posits; Lithosphere; Marine vents; Oil and natural gas distribution; Oil and natural gas reservoirs; Ophio- lites; Plate tectonics; Plutonic rocks and mineral de- posits; Seafloor spreading; Volcanoes. Earthwatch Institute Category: Organizations, agencies, and programs Date: Established 1971 Earthwatch is an international nonprofit organiza- tion that advocates research and scientific literacy to help resolve environmental issues such as sustainable resource management. Earthwatch supports scientific research projects and assigns volunteers to those proj- ects; builds networks to share expedition-based curricu- lums and lessons; collaborates with other conservation and environmental organizations; and solicits corpo - rate partners and private individuals to help promote a sustainable environment. 326 • Earthwatch Institute Global Resources Background Founded in 1971, in Boston, Massachusetts, Earth- watch Institute began with four Smithsonian scientists and small teams of volunteers. Earthwatch was estab- lished as government funds for scientific research de- creased. The organization sought a funding model that would bridge research with action to increase public scientific literacy and involvement. Earthwatch Institute is the world’s largest environ- mental volunteer nonprofit organization. The mis- sion of Earthwatch is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment. The Earthwatch community includes research scientists, educators, students, global mem- bers, volunteers, collaborating conservation organi- zations, and corporate partners. Earthwatch Institute is a public charity under the U.S. Internal Revenue Code. The organization has headquarters in Australia, Belize, Costa Rica, England, Japan, Kenya, and the United States. Impact on Resource Use Earthwatch prioritizes and supports effective scien- tific research that focuses on sustainable resource management, climate change, oceans, and sustain- able cultures. Such projects include data on species, habitats, and protected areas. Scientific results are published worldwide in scholarly journals and shared with partner organizations, government agencies, and policy makers. Earthwatch research results have confirmed that sustainable resource management is crucial not only to social and economic development but also to un- derstanding ecosystem complexities. Such studies in- clude the Amazon Riverboat Exploration, which found that since local communities have been actively involved in the management of the Pacaya-Samiria National Reserve in the Peruvian Amazon there has been a decrease in hunting and an increase in popula- tions of certain wildlife species. Other Earthwatch research focuses on ways that various species are affected by climate change and may suggest ways to mitigate negative impacts, such as those caused by human activities. In 2006, James Crabbe received an award for his outstanding re- search on coral reefs in Jamaica and Belize. He uses a remotely operated vehicle (ROV) to obtain digital im - ages and measure growth of coral at depths that are difficult or impossible to reach by diving. His research results include findings that the rising Jamaican water temperature has caused a measurable decline in coral cover. Earthwatch supports research on the stability and productivity of life in oceans and coastal regions. In 2007, Earthwatch completed the first baseline survey of species inhabiting the subtidal and intertidal zones of the Seychelles. The study had the support of the Mitsubishi Corporation. Research data, including photographic documentation, were shared with the Seychelles government, local communities, and con- servation groups. With assistance from project scien- tists, teacher volunteers in the Seychelles and United Kingdom have developed ecology curriculum re- sources for educational use. An Earthwatch focus on both current and past sus- tainable cultures contributes to a better understand- ing of human interaction with the environment. Re- search on ancient civilizations, such as that which inhabited the Rapa Nui, or Easter Island, provides assessments on behavioral change, attitudes, and ad- aptation. Chris Stevenson has led the project for ap- proximately two decades. Research findings include information linking climatic changes with changes in farming that may be helpful in analyzing modern environmental problems. June Lundy Gastón Web Site EarthWatch http://www.earthwatch.org See also: Biodiversity; Biotechnology; Resources for the Future; Sustainable development. Ecology Category: Scientific disciplines Ecology is the scientific study of the interrelationships among organisms—including their habitats, distribu- tion, and abundance—and the relationships of these organisms with their environment, known as bio- nomics. From a global perspective, ecology concerns many issues that affect the interaction and connec- tions between living and nonliving environments, and, hence, the availability, distribution, and use of global resources. Global Resources Ecology • 327 Background In the 1860’s, Ernst Haeckel, a German scientist, coined the word “ecology” based on the Greek word oikos, which means “house.” The terminology is apt, because ecology focuses on the complex environmen- tal conditions that form organisms’ habitats. His- torically, ecology was rooted in natural history, which in the 1800’s sought to describe the diversity of life and evolutionary adaptations to the environment. In modern usage, ecology includes the study of the inter- actions among organisms—such as humans, animals, insects, microbes, and plants—and their physical or abiotic environment. The abiotic environment con- cerns factors such as climate (air and temperature), hydrology (water), geological substrate (soil), light, and natural disasters that affect the environment. The abiotic factors are essential for sustaining the life of organisms. Ecology also involves the study of biotic environ- mental components that influence habitats and the distribution and abundance of species of organisms in geographic space and time. The interaction be- tween living organisms and the nonliving environ- ment in a self-contained area is known as an ecosys- tem. Ecologists study processes such as how energy and matter move though interrelated ecosystems like ponds, forest glades, or rocks with moss growing on them. Maintaining an ecosystem requires the proper balance of air, water, soil, sunlight, minerals, and nu- trients. Ecological Levels Modern ecology is interdisciplinary and is based on multiple classifications. Descriptive unit classifica- tions based on the study of organisms and processes start with the simplest and build to the most complex, from individuals to populations, species, communi- ties, ecosystems, and biomes. • Physiological ecology, the simplest classification, concerns the interaction of individual organisms with their life-sustaining abiotic environment and the impact ofbioticcomponentsontheirhabitats. • Population ecology is the study of the interaction of individuals of different species (whether bacte- rium, plant, or animal) that occupy the same loca- tion and are genetically different from other such groups. • Community ecologists analyze the interaction of in - terdependent species populations living within a given habitat or area, known as an ecological com - munity. • Ecosystem ecology includes the nonliving environ- ment and concerns decomposition of living organ- isms and intake of inorganic materials into living organisms. In other words, ecosystem ecologists study the flow of energy and the cycling of nutrients through the abiotic and biotic environments of in- teracting ecological communities. • The interaction of multiple ecosystems with one an- other is known as a biome. Some familiar biomes in- clude coniferous forests, rain forests, tundra re- gions, deserts, coral reefs, and oceans. • Finally, scientists involved in biosphere ecology study the interaction of all matter and living organ- isms on the planet. Ecological Subfields The terminology used for other ecological classifica- tions emphasizes the interdisciplinary nature of ecol- ogy. Paleoecology, for example, involves archaeology in the study of ancient remains and fossils in order to analyze the interrelationships of historic organisms and reconstruct ancient ecosystems. Using evolution- ary theory, behavioral ecologists consider the roles of behavior in enabling organisms to adapt to new and changed environments. In systems ecology, scientists use systems theory to manage energy flows and bio- geochemical cycles in ecosystems. With some basis in anthropology, political ecologists seek equilibrium in political, economic, and social decision making that impacts the environment. Landscape ecologists con- duct spatial analyses and examine processes and in- terrelationships of ecosystems over large, regional geographic areas. Global ecology is the study of inter- relationships between organisms and their environ- ment on a global scale. Genetic Ecology Two emerging specialty subfields of ecology are ge- netic and evolutionary ecology. In genetic ecology, scientists study genetic variations in species that lead to the evolution of new species or to the adaptation of existing species to new or changed environments. These new or changed environments may be the re- sult of many factors, including abiotic changes, such as an increase or decrease in temperature; increased predation of a species, including overhunting or over - fishing; or an unsustainable increase in population. When the environment changes or ecosystems are dis - 328 • Ecology Global Resources turbed, species must adapt or face extinction. Genetic ecology considers genetic factors that allow some spe- cies to adapt to and survive environmental changes more easily. In some recent studies of plant species sci- entists used genetic ecology to analyze how quickly specific plants migrate and adapt to new habitats in re- sponse to climate change. Although earlier predic- tions indicated that plant migration would keep up with environmental change, recent studies indicate that migration will be slower than originally believed. Genetic ecology is also an important tool in studying animal species as well as managing wild and captive animal populations andimprovingpopulationhealth. Genetic ecologists are involved in genetic engi- neering in order to assess the relationship between genetics of a species and the ecosystem that supports the survival of that species. One argument is that an organism’s genetic structure fits exactly with the ex- ternal ecosystem that supports its survival, especially the external and life-sustaining oxygen-carbon diox- ide system. The concern is that interspecies genetic engineering will upset the delicate ecological balance that allows a species to maintain its existence within a specific ecosystem and will adversely affect the con - tinuous and systematic reproduction of ecosystems supported by symbiotic relationships, such as an or- ganism’s energy production and processing systems. Unless an organism is able to evolve by adapting its ge- netic structures to changes in an ecosystem, it is un- likely to survive. An example of genetic engineering that may adversely affect the environment and other living organisms involves pest-resistant corn. Pollen of some corn genetically modified to code for Bacillus thuringiensis was initially thought to threaten mon- arch butterflies. Later studies showed this not to be the case, but a greater concern emerged: So-called Bt corn may encourage the development of resistant pests, which could then threaten corn crops. Until the emergence of a better understanding of the relation- ships between genetic structures of all living organ- isms and the relationshipsoforganisms toecosystems, genetic engineering may present serious dangers. Evolutionary Ecology Evolutionary ecology brings together ecology, biol- ogy, and evolution. Evolutionary ecologists look at the Global Resources Ecology • 329 The Blue Ridge Mountains, part of the Appalachian Mountains in the eastern United States, represent both biological and political issues that concern the modern ecologist. (AP/Wide World Photos) . management of global resources. Background In the 1960’s, the issue of environmental protection was gaining prominence in the United States and in other developed countries. As part of this political climate,. Natural Resources Conservation Service; Soil management; Weather and resources. Dynamite Category: Obtaining and using resources The invention of dynamite has had an effect on the procuring of coal,. The Statement of Forest Principles, another nonbinding statement adopted at the Earth Summit, pertains to the manage- ment of global forest resources and indicates a recog- nition of the differential