Climate change affects the Earth’s vegetation by altering normal cooling and warming cycles. On a short-term basis, warming of the atmosphere due to increased carbon dioxide and other greenhouse gases enhances ecosystems. Higher than normal carbon dioxide levels increase the photosynthetic activity, and this makes plants more efficient in using water, perhaps forestalling drought. Over long periods, however, global climate change hurts biodiversity by the mechanisms suggested by the United Nations Environment Programme’s World Conservation Monitoring Center and summarized in the following table.
Climate Change Effects on Ecosystems
wetlands : drying out, imbalanced water cycle
coastal marshes : habitat loss in estuaries and deltas due to sea level rise and flooding
tropical forests : drought, invasive species
boreal forests : increased incidence of fires and pests
the Arctic : expansion of boreal forests into arctic habitat, loss of tundra, thawing of permafrost
alpine mountains : habitat shift into higher altitudes, loss of highaltitude habitats, rapid snow melt
low-lying mountains : loss of land to rising sea levels, loss of seabird nesting colonies, human encroachment on habitats
arid and semiarid areas : deserts become hotter and drier, increased desertification, salinization, loss of grasslands and arable land
coral reefs : coral bleaching and death, altered growth rates
mangrove swamps : decrease in area
Climate change alters ecosystems by changing vegetation growth and weather patterns. First, climate change alters the growing season for plants and trees and so affects the species whose breeding cycles depend on these plants and trees. For example, a tree that blossoms at a different time on the calendar affects the insects that carry pollen, and the altered insect populations influence the feeding opportunities for birds and reptiles. Second, new weather patterns that increase the violence and frequency of storms or the severity of heat waves and drought also affect the health of species and their resistance to disease and pests.
Al Gore wrote in his landmark 2006 book, An Inconvenient Truth, “. . . we are facing what biologists are beginning to describe as a mass extinction crisis, with a rate of extinction now 1,000 times higher than the normal background rate. Many of the factors contributing to this wave of extinction are also contributing to the climate crisis. The two are connected. For example, the destruction of the Amazon rain forest drives many species to extinction and simultaneously adds more carbon dioxide to the atmosphere.” Many animals already struggle to keep pace with climate change. Polar bears go hungry waiting for the Arctic ice to form from which the bears hunt for seal; fish and crustaceans cannot breed in water too warm to supply their food; and the broods of migrating birds starve because the seedlings and insects they usually eat have come and gone because of changing weather patterns.
Source of Information : Green Technology Biodiversity
2012年5月29日
2012年5月27日
The Father of Taxonomy
Taxonomy is a branch of biology concerned with naming and classifying organisms based on their relationship to each other. The taxonomy in use today originated with Carl Linnaeus (also Carolus or Carl von Linne), born in 1707 in Stenbrohult, Sweden. Young Linnaeus possessed a love of plants, which he put to use as an adult working for Sweden’s Royal Science Society. Linnaeus traveled the country collecting specimens for the society and in the process developed a reputation as a skilled botanist. In 1735 he moved to the Netherlands to devote time to the science of plant life and the resemblances he saw between certain seemingly unrelated plants. Linnaeus rearranged plant classifications that had been used in biology since Aristotle and published a new scheme in Genera Plantarum. The scheme contained groupings based on detailed likenesses between species rather than gross appearances.
Linnaeus’s new hierarchy met with a combination of criticism and indifference from the scientific community, so he retreated to Sweden, married, and became professor of natural sciences at the University of Uppsala. But he continued studying plant life based on similarities and differences in structure, color, reproduction, and other physical traits, and published Species Plantarum in 1753. A younger generation of botanists understood the value of classifying plants to the species level, as Linnaeus had proposed. Linnaeus received satisfaction for more than just scientific merit; part of his motivation had come from a desire to honor God’s plan by understanding the world of living things.
The hallmark of the Linnaeus system resides in characteristics called differentia specifica. These unique characteristics make every organism distinct from all others and enable biologists to classify each new organism they discover without confusing it with others already described. The system additionally made order of all species by grouping them into genera, genera into orders, orders into classes, and classes into two kingdoms. Most significantly, each species can be distinguished by a name that contains both genus and species. Therefore biologists speak of tigers as Panthera tigris, an iguana as Dipsosaurus dosalis, a redwood tree as Sequoia sempervirens, and so on.
Following Linnaeus’s death in 1784, taxonomists paid closer attention to species ancestry. In 1857 Carl von Nageli proposed that fungi and bacteria be placed in the plant kingdom, but Ernst Haeckel suggested in 1866 that bacteria, protozoa, algae, and fungi belonged to a new kingdom called Protista because they seemed related to neither plants nor animals.
Biologists today use nucleic acid sequencing to trace ancestral roots and electron microscopy to study minute differences in cell structures. These methods have enabled taxonomists to alter schemes that had not changed in 100 years. Studies on deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) reveal that all living things belong to one of three domains: Bacteria, Archaea, or Eukarya. Molecular biology may uncover additional ways to classify organisms so that the present system may again change in coming years. Linnaeus’s dedication to finding a standard system for classifying biota built a standard for generations of scientists to follow.
Source of Information : Green Technology Biodiversity
Linnaeus’s new hierarchy met with a combination of criticism and indifference from the scientific community, so he retreated to Sweden, married, and became professor of natural sciences at the University of Uppsala. But he continued studying plant life based on similarities and differences in structure, color, reproduction, and other physical traits, and published Species Plantarum in 1753. A younger generation of botanists understood the value of classifying plants to the species level, as Linnaeus had proposed. Linnaeus received satisfaction for more than just scientific merit; part of his motivation had come from a desire to honor God’s plan by understanding the world of living things.
The hallmark of the Linnaeus system resides in characteristics called differentia specifica. These unique characteristics make every organism distinct from all others and enable biologists to classify each new organism they discover without confusing it with others already described. The system additionally made order of all species by grouping them into genera, genera into orders, orders into classes, and classes into two kingdoms. Most significantly, each species can be distinguished by a name that contains both genus and species. Therefore biologists speak of tigers as Panthera tigris, an iguana as Dipsosaurus dosalis, a redwood tree as Sequoia sempervirens, and so on.
Following Linnaeus’s death in 1784, taxonomists paid closer attention to species ancestry. In 1857 Carl von Nageli proposed that fungi and bacteria be placed in the plant kingdom, but Ernst Haeckel suggested in 1866 that bacteria, protozoa, algae, and fungi belonged to a new kingdom called Protista because they seemed related to neither plants nor animals.
Biologists today use nucleic acid sequencing to trace ancestral roots and electron microscopy to study minute differences in cell structures. These methods have enabled taxonomists to alter schemes that had not changed in 100 years. Studies on deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) reveal that all living things belong to one of three domains: Bacteria, Archaea, or Eukarya. Molecular biology may uncover additional ways to classify organisms so that the present system may again change in coming years. Linnaeus’s dedication to finding a standard system for classifying biota built a standard for generations of scientists to follow.
Source of Information : Green Technology Biodiversity
2012年5月23日
The Ivory-Billed Woodpecker
The large ivory-billed woodpecker once nested throughout the southeastern United States and thrived in great expanses of virgin woodland that covered much of the region before the Civil War. These tracts of swampland, nicknamed the “Big Woods,” surrounding Arkansas’s Cache River, are called bottomland hardwoods and contain many dead and dying trees. Bottomland hardwoods attract beetles and so become a source of beetle larvae, the ivory-bill’s favorite food. After the Civil War, the lumber industry cut down swaths of hardwoods for building homes, and by the 1940s the bottomland had shrunk. Few residents living nearby saw the woodpecker again. On March 11, 1967, the FWS added the ivorybilled woodpecker to the endangered species list, though most biologists felt it was already extinct.
In 2004 a current of excitement ran through the world of ornithology. A kayaker paddling the Cache River had spotted a bird he believed was an ivory-billed woodpecker. Soon afterward two others caught on film a brief glimpse of a bird having the woodpecker’s characteristic markings. The director of the Cornell Lab of Ornithology, John Fitzpatrick, told National Geographic, “Through the 20th century it’s been every birder’s fantasy to catch a glimpse of this bird, however remote the possibility. This really is the holy grail.” Recordings taken in the densest parts of the bottomlands gave evidence of the ivory-bill’s distinctive double rap-rap on tree trunks. Birdwatchers converged on the Cache River and nearby White River National Wildlife Refuge, the last remaining places believed to support the special bird. Frank Gill of New York’s Audubon Society remarked, “It is kind of like finding Elvis.” Since 2004 persistent volunteers have made no additional sightings, though the Cornell group and the Nature Conservancy have devoted 3,000 hours of in-person searches and movemen tcontrolled photography. Robotic sensors scan the woods for any and all movements, while the Automated Collaborative Observatory for Natural Environments (ACONE) searches the Arkansas skies on the lookout for birds of any type.
Did a species thought to be extinct somehow manage to recover and begin to repopulate the area? The last tentative sighting occurred in 2005, but ecologists have wisely gone on the offensive in preserving what is left of the woodpecker’s habitat. Mr. Fitzpatrick told the Boston Globe in 2008, “The decline of the ivory-billed is an unspeakable American tragedy. This country was unable to save even a single square meter of pristine bottomland habitat. It all went under the ax and chainsaw. We may have lost this iconic bird, but, by God, we owe the ivory-billed this sort of exhaustive, scientific search. . . . If they are there, we also owe them a recovery program.” The Nature Conservancy has worked jointly with the FWS to set aside thousands of acres of woodpecker habitat. “The successful history of conservation in the Big Woods of Arkansas,” said the Nature Conservancy’s Scott Simon, “is the result of great partnerships—federal and state agencies working with other organizations, local communities, hunters and landowners.” The emotional support from people like Fitzpatrick plus government support provide the best chance for saving critically endangered species.
In 2007 the FWS designed a recovery plan for the ivory-billed woodpecker, should it indeed still hide in the swamps. The agency focuses on the following three goals: verify the existence of the bird by sightings, recordings, or nest cavities in trees; protect or add to current habitat; and study all factors that would threaten a potential ivory-billed colony. In an encouraging example of positive thinking, the FWS has set a goal of 2075 for the year in which the ivory-billed woodpecker will be removed from the endangered species list, a step called delisting.
The scientific community’s and the public’s reaction to the ivory-billed woodpecker sighting attests to the current state of many species that were once abundant. The ivory-billed woodpecker experience—whether or not the bird still lives—has offered good examples of the quick reactions and sound planning needed to preserve disappearing species.
Source of Information : Green Technology Biodiversity
In 2004 a current of excitement ran through the world of ornithology. A kayaker paddling the Cache River had spotted a bird he believed was an ivory-billed woodpecker. Soon afterward two others caught on film a brief glimpse of a bird having the woodpecker’s characteristic markings. The director of the Cornell Lab of Ornithology, John Fitzpatrick, told National Geographic, “Through the 20th century it’s been every birder’s fantasy to catch a glimpse of this bird, however remote the possibility. This really is the holy grail.” Recordings taken in the densest parts of the bottomlands gave evidence of the ivory-bill’s distinctive double rap-rap on tree trunks. Birdwatchers converged on the Cache River and nearby White River National Wildlife Refuge, the last remaining places believed to support the special bird. Frank Gill of New York’s Audubon Society remarked, “It is kind of like finding Elvis.” Since 2004 persistent volunteers have made no additional sightings, though the Cornell group and the Nature Conservancy have devoted 3,000 hours of in-person searches and movemen tcontrolled photography. Robotic sensors scan the woods for any and all movements, while the Automated Collaborative Observatory for Natural Environments (ACONE) searches the Arkansas skies on the lookout for birds of any type.
Did a species thought to be extinct somehow manage to recover and begin to repopulate the area? The last tentative sighting occurred in 2005, but ecologists have wisely gone on the offensive in preserving what is left of the woodpecker’s habitat. Mr. Fitzpatrick told the Boston Globe in 2008, “The decline of the ivory-billed is an unspeakable American tragedy. This country was unable to save even a single square meter of pristine bottomland habitat. It all went under the ax and chainsaw. We may have lost this iconic bird, but, by God, we owe the ivory-billed this sort of exhaustive, scientific search. . . . If they are there, we also owe them a recovery program.” The Nature Conservancy has worked jointly with the FWS to set aside thousands of acres of woodpecker habitat. “The successful history of conservation in the Big Woods of Arkansas,” said the Nature Conservancy’s Scott Simon, “is the result of great partnerships—federal and state agencies working with other organizations, local communities, hunters and landowners.” The emotional support from people like Fitzpatrick plus government support provide the best chance for saving critically endangered species.
In 2007 the FWS designed a recovery plan for the ivory-billed woodpecker, should it indeed still hide in the swamps. The agency focuses on the following three goals: verify the existence of the bird by sightings, recordings, or nest cavities in trees; protect or add to current habitat; and study all factors that would threaten a potential ivory-billed colony. In an encouraging example of positive thinking, the FWS has set a goal of 2075 for the year in which the ivory-billed woodpecker will be removed from the endangered species list, a step called delisting.
The scientific community’s and the public’s reaction to the ivory-billed woodpecker sighting attests to the current state of many species that were once abundant. The ivory-billed woodpecker experience—whether or not the bird still lives—has offered good examples of the quick reactions and sound planning needed to preserve disappearing species.
Source of Information : Green Technology Biodiversity
2012年5月18日
Value of Riparian Ecosystems
Riparian areas hold rich biodiversity and their food webs can become quite complex. In addition to providing habitat, shelter, food, and water for the animals of riparian ecosystems, these systems also provide general benefits to the environment.
Riparian areas possess moist soil rich in organic matter replenished by periodic flooding. Unique physical features provide habitat for some biota that live nowhere else but along streams and rivers, some for their entire lives. Other species use riparian areas only at certain times of the day, in particular seasons, or in specific stages of their life cycle. Songbirds, for example, come and go, but they depend on riparian areas, perhaps because songbirds do not possess exceptional hunting skills and the density of plant and insect life along streams suits them. Many owls also station themselves in riparian areas for hunting nocturnal animals seeking water. Any predator gains an advantage by hunting in a locale where food comes to them rather than expending energy to find and stalk prey.
Riparian ecosystems also affect the neighboring land, especially in flat open countryside where vegetation next to the water offers an oasis from heat and a refuge from winter winds. The unique physical features of riparian areas create a microenvironment, a defined place that has its own climate. Riparian areas occur in low-lying places so they hold moisture and humidity longer than open spaces. The high moisture and shady conditions help these areas reduce extremes in temperature and humidity, partially explaining why many species use riparian habitat to raise offspring. The moisture and shade also moderates air temperature in the riparian area. Taken together, riparian areas offer stability in climate, temperature, plant life, and animal life. It is no wonder that animals living in sparse, arid conditions—on the plains or on the savanna, for instance—probably view riparian habitat as an important means of sustenance.
Humans have encroached to the very edge of many urban rivers and streams so that these ecosystems have been severely altered. Even regions with fewer people put pressure on the species that live only in riparian habitat. Livestock ranchers value riparian areas for watering their herds, which ruins the bank. From the 1700s through the 1800s, timber companies used fast-flowing streams to carry logs down mountains to sawmills,
and farmers have used them as an easy source of irrigation water and good soil for crops.
Even wild animals in arid regions can in time damage stream sides and riverbanks. Riparian habitats in Africa, for example, serve as places where elephants, rhinoceroses, and herds of hoofed animals come in to drink. These large animals need water, but as they visit the same sites by day or by night they do significant damage to the habitat.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
Riparian areas possess moist soil rich in organic matter replenished by periodic flooding. Unique physical features provide habitat for some biota that live nowhere else but along streams and rivers, some for their entire lives. Other species use riparian areas only at certain times of the day, in particular seasons, or in specific stages of their life cycle. Songbirds, for example, come and go, but they depend on riparian areas, perhaps because songbirds do not possess exceptional hunting skills and the density of plant and insect life along streams suits them. Many owls also station themselves in riparian areas for hunting nocturnal animals seeking water. Any predator gains an advantage by hunting in a locale where food comes to them rather than expending energy to find and stalk prey.
Riparian ecosystems also affect the neighboring land, especially in flat open countryside where vegetation next to the water offers an oasis from heat and a refuge from winter winds. The unique physical features of riparian areas create a microenvironment, a defined place that has its own climate. Riparian areas occur in low-lying places so they hold moisture and humidity longer than open spaces. The high moisture and shady conditions help these areas reduce extremes in temperature and humidity, partially explaining why many species use riparian habitat to raise offspring. The moisture and shade also moderates air temperature in the riparian area. Taken together, riparian areas offer stability in climate, temperature, plant life, and animal life. It is no wonder that animals living in sparse, arid conditions—on the plains or on the savanna, for instance—probably view riparian habitat as an important means of sustenance.
Humans have encroached to the very edge of many urban rivers and streams so that these ecosystems have been severely altered. Even regions with fewer people put pressure on the species that live only in riparian habitat. Livestock ranchers value riparian areas for watering their herds, which ruins the bank. From the 1700s through the 1800s, timber companies used fast-flowing streams to carry logs down mountains to sawmills,
and farmers have used them as an easy source of irrigation water and good soil for crops.
Even wild animals in arid regions can in time damage stream sides and riverbanks. Riparian habitats in Africa, for example, serve as places where elephants, rhinoceroses, and herds of hoofed animals come in to drink. These large animals need water, but as they visit the same sites by day or by night they do significant damage to the habitat.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
2012年5月15日
Riparian Ecosystems
A typical riparian ecosystem consists of life that has evolved in flowing freshwater rather than in static waters. Any ecosystem that has adapted to living in running water is called a loticecosystem. Part of the riparian ecosystem also consists of animals that use areas as migration corridors and feed on riparian plants and animals. Riparian ecosystems represent edges, a place where two different habitats meet. Lush and shady conditions next to a stream, for example, differ from the sunny dry meadow a short distance from the stream. Some predators seek edges because they contain a greater number and variety of prey animals, and when predators hunt in riparian habitats, they also become part of the ecosystem.
Rivers and streams are general terms for bodies of flowing water: rivers
are larger and usually empty into an ocean, bay, or large lake; streams
are smaller and empty into larger streams, rivers, and seashores. The following
four types of rivers or streams make up riparian habitat:
» perennial (or permanent) rivers/streams—flow year-round
» intermittent rivers/streams—flow only in certain seasons, after storms, or when snow melts
» ephemeral rivers/streams—flow for short periods of time in rainy seasons, but hold shape year-round
» interrupted rivers/streams—flow aboveground in some places and belowground in others
Riparian habitat contains only a one-way flow of freshwater— downhill— and with the capacity to transport sediment and reshape the land. Therefore, ecosystems at the low-volume head of a river—even the Mississippi River starts as a stream—differ greatly from the ecosystems in a large tributary a few miles from the sea.
The ecosystems in large slow-moving rivers resemble lake ecosystems. Phytoplankton, tiny invertebrate plant life, dominates the open waters and captures the Sun’s energy by photosynthesis. River food chains build upon the single-celled phytoplankton, with larger invertebrates, fish, and predator fish toward the top of the food chain. As water flows faster, phytoplankton density falls, and the water becomes clearer. Phytoplankton may build up, however, in swirling pools carved from the riverbank by fast-flowing rivers or produced by rocks. These areas of choppy water called riffles provide young fish with a safe place to hide from predators and to eat. When the fish grow large enough, they leave the riffles and spend the rest of their time in the main body of water.
Some large rivers contain extensive wetlands that provide safety for fish spawning and for waterfowl to hatch eggs and raise their young. These areas, called backwaters, also provide the normal benefits of wetlands: cleaning water of pollution; removing silt; providing specialized habitat; and controlling floodwaters.
Streambeds contain a mixture of organic (phytoplankton, zooplankton, insects, worms) and inorganic (sediment, rocks, insoluble minerals) nutrients. Faster-flowing streambeds contain less of these nutrients than slow-flowing streambeds, but because streams are shallow, terrestrial creatures make use of them as well as aquatic life. Rocks in streams also contain slippery sheets of bio film that hold a mixture of organic and inorganic matter captured from the flowing water.
Streams also house an assortment of insects, insect larvae, and nymph forms, and invertebrates that transfer energy from plant life to a form usable by predators. Leeches, worms, mollusks, and crustaceans make up the next level in the riparian food chain. These lower levels of the food chain nourish fish, large insects, reptiles, amphibians, and birds. Waterfowl, rabbits, and rodents eat aquatic grasses and plants along the stream’s banks. The riparian ecosystem contains the varied components that characterize healthy ecosystems, while it harbors changing conditions affected by heavy rainfalls, flooding, and droughts.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
Rivers and streams are general terms for bodies of flowing water: rivers
are larger and usually empty into an ocean, bay, or large lake; streams
are smaller and empty into larger streams, rivers, and seashores. The following
four types of rivers or streams make up riparian habitat:
» perennial (or permanent) rivers/streams—flow year-round
» intermittent rivers/streams—flow only in certain seasons, after storms, or when snow melts
» ephemeral rivers/streams—flow for short periods of time in rainy seasons, but hold shape year-round
» interrupted rivers/streams—flow aboveground in some places and belowground in others
Riparian habitat contains only a one-way flow of freshwater— downhill— and with the capacity to transport sediment and reshape the land. Therefore, ecosystems at the low-volume head of a river—even the Mississippi River starts as a stream—differ greatly from the ecosystems in a large tributary a few miles from the sea.
The ecosystems in large slow-moving rivers resemble lake ecosystems. Phytoplankton, tiny invertebrate plant life, dominates the open waters and captures the Sun’s energy by photosynthesis. River food chains build upon the single-celled phytoplankton, with larger invertebrates, fish, and predator fish toward the top of the food chain. As water flows faster, phytoplankton density falls, and the water becomes clearer. Phytoplankton may build up, however, in swirling pools carved from the riverbank by fast-flowing rivers or produced by rocks. These areas of choppy water called riffles provide young fish with a safe place to hide from predators and to eat. When the fish grow large enough, they leave the riffles and spend the rest of their time in the main body of water.
Some large rivers contain extensive wetlands that provide safety for fish spawning and for waterfowl to hatch eggs and raise their young. These areas, called backwaters, also provide the normal benefits of wetlands: cleaning water of pollution; removing silt; providing specialized habitat; and controlling floodwaters.
Streambeds contain a mixture of organic (phytoplankton, zooplankton, insects, worms) and inorganic (sediment, rocks, insoluble minerals) nutrients. Faster-flowing streambeds contain less of these nutrients than slow-flowing streambeds, but because streams are shallow, terrestrial creatures make use of them as well as aquatic life. Rocks in streams also contain slippery sheets of bio film that hold a mixture of organic and inorganic matter captured from the flowing water.
Streams also house an assortment of insects, insect larvae, and nymph forms, and invertebrates that transfer energy from plant life to a form usable by predators. Leeches, worms, mollusks, and crustaceans make up the next level in the riparian food chain. These lower levels of the food chain nourish fish, large insects, reptiles, amphibians, and birds. Waterfowl, rabbits, and rodents eat aquatic grasses and plants along the stream’s banks. The riparian ecosystem contains the varied components that characterize healthy ecosystems, while it harbors changing conditions affected by heavy rainfalls, flooding, and droughts.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
2012年5月13日
Three Gorges Dam
China’s massive project to construct the Three Gorges Dam across the flood-prone Yangtze River brings together almost all of environmentalists’ fears. The Three Gorges Dam controls a drainage area of 386,300 square miles (1 million km2) and when complete it will be the world’s largest water conservation structure. The project’s leaders have assured their country and the world that the Three Gorges Dam will be a masterpiece of flood control and energy generation. Critics have cited other factors associated with the dam that will have worse effects on the environment.
Criticism of the dam centers on three health threats: (1) increased disease due to larger mosquito and other pest breeding grounds; (2) downstream droughts when flow is diverted for energy production; and (3) increased incidence of earthquakes due to the size of the structure in the Earth’s crust. George Davis, a specialist in tropical medicine at George Washington University in Washington, D.C., cautioned in 2008, “When it comes to environmental change, the implementation of the Three Gorges dam and reservoir is the great granddaddy of all changes. Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region, you change a lot of environmental variables. Almost all infectious diseases are up for grabs.” Davis argues that the standing waters behind the dam create perfect conditions for swimmers to catch infections from polluted water, be invaded by parasites, and attacked by mosquitoes.
Since the Three Gorges building project began at the close of 1994, ecologists have wondered about all the environmental changes about to begin. Warnings came early in the construction, but the Chinese government found no reason to question the dam’s value. By 2007, however, leaders in China admitted that the environmentalists’ cautions about the Three Gorges project might have been right. The Xinhua news agency published the following statement released by the Chinese ruling party: “There exist many ecological and environmental problems concerning the Three Gorges Dam. If no preventive measures are taken, the project could lead to catastrophe.” All of the ecosystem damages, upstream and downstream, have begun to emerge in the Three Gorges project. The difference between this and other dams is the magnitude of the potential problems.
Sediments accumulating in the water behind the dam have prompted environmental engineers to worry about structural failure. Also, flooding of the lake behind the dam would cause lake waters to spread to sewer systems and landfills, and thus pollute the water when the lake recedes. These problems could occur in addition to the normal disadvantages to the environment that dams are known to cause.
Navigation has returned to normal on China’s important Yangtze River—a lock system raises or lowers oceangoing vessels—and some of the dam’s 26 generators have begun to produce energy. The dam uses two power plants on either side of the structure to produce 84 billion kilowatt-hours, or almost 1.5 times the energy produced by the world’s second-largest dam, which is shared by Brazil and Paraguay. The project’s leaders stress that this amount of energy will replace 40–50 million tons (36–45 million metric tons) of coal each year. Three Gorges Dam provides an example of the environmental questions, both troubling and hopeful, raised by massive dams.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
Criticism of the dam centers on three health threats: (1) increased disease due to larger mosquito and other pest breeding grounds; (2) downstream droughts when flow is diverted for energy production; and (3) increased incidence of earthquakes due to the size of the structure in the Earth’s crust. George Davis, a specialist in tropical medicine at George Washington University in Washington, D.C., cautioned in 2008, “When it comes to environmental change, the implementation of the Three Gorges dam and reservoir is the great granddaddy of all changes. Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region, you change a lot of environmental variables. Almost all infectious diseases are up for grabs.” Davis argues that the standing waters behind the dam create perfect conditions for swimmers to catch infections from polluted water, be invaded by parasites, and attacked by mosquitoes.
Since the Three Gorges building project began at the close of 1994, ecologists have wondered about all the environmental changes about to begin. Warnings came early in the construction, but the Chinese government found no reason to question the dam’s value. By 2007, however, leaders in China admitted that the environmentalists’ cautions about the Three Gorges project might have been right. The Xinhua news agency published the following statement released by the Chinese ruling party: “There exist many ecological and environmental problems concerning the Three Gorges Dam. If no preventive measures are taken, the project could lead to catastrophe.” All of the ecosystem damages, upstream and downstream, have begun to emerge in the Three Gorges project. The difference between this and other dams is the magnitude of the potential problems.
Sediments accumulating in the water behind the dam have prompted environmental engineers to worry about structural failure. Also, flooding of the lake behind the dam would cause lake waters to spread to sewer systems and landfills, and thus pollute the water when the lake recedes. These problems could occur in addition to the normal disadvantages to the environment that dams are known to cause.
Navigation has returned to normal on China’s important Yangtze River—a lock system raises or lowers oceangoing vessels—and some of the dam’s 26 generators have begun to produce energy. The dam uses two power plants on either side of the structure to produce 84 billion kilowatt-hours, or almost 1.5 times the energy produced by the world’s second-largest dam, which is shared by Brazil and Paraguay. The project’s leaders stress that this amount of energy will replace 40–50 million tons (36–45 million metric tons) of coal each year. Three Gorges Dam provides an example of the environmental questions, both troubling and hopeful, raised by massive dams.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
2012年5月9日
Dams
One of the most dramatic physical alterations of waterways arises from the building of dams. Large dam projects began in the United States in the 1930s with good intentions, but ecologists now realize that dams affect ecosystems, natural water flows, and water conservation in both good and bad ways.
Dams provide benefits in water management in the following ways: (1) They conserve water by storing it in reservoirs; (2) they supply irrigation water; and (3) they reduce flooding downstream. In addition, many dams have been built for the main purpose of producing electricity. All of these factors have helped preserve people’s property, and the waterpower from dams serves as a sustainable energy source.
Dams conserve water in two ways: Reservoir water behind dams serves as low-cost storage for a community’s drinking supply, and the downstream flow provides a constant source of irrigation water. Both situations conserve groundwater. Lakes behind dams provide outdoor recreation areas and places for fishing, perhaps sparing wilderness areas from excess human activities. For each of these positives, however, there is also a disadvantage, summarized in the table below.
When dams interfere with natural water flows, they affect aquatic ecosystems that live in riparian habitats. Dams do this by changing the normal flow of sediments that carry nutrients to microbes and invertebrates, taking away long stretches of running water that some migrating fish need, and slowing water flow enough to allow salt water from estuaries to move upstream. Salt water contamination kills the diverse microbes, invertebrates, amphibians, fish, and plants that need freshwater.
Two opposing schools of thought have grown regarding the role of dams in the environment today, and not surprisingly, the arguments become contentious. Butch Hopkins of California’s Reclamation Board explained the major issue swirling around the American River’s Auburn Dam to the Sacramento Bee in 2006: “The dam is incredibly controversial because it runs flat into the fundamental beliefs of fiscal conservatives and environmentalists.” Those words describe almost all large dam projects in place today.
Dams allow communities to take advantage of a renewable energy source while they also practice water conservation. But environmentalists have called for the removal of large and small dams, and in the past few decades many dams have in fact come down, either because they had become dangerously degraded or because they were part of a riparian restoration. Three environmental groups—Friends of the Earth, Trout Unlimited, and American Rivers—published a report together in 1999 that detailed case studies of dam removal projects. Dam Removal Success Stories summarized the rationale behind dam removal: “Even for some functioning dams, removal may be a sound solution when a dam’s benefits are outweighed by the significant environmental damage it causes. . . . Clearly dam removal is not appropriate for all—or even most—of the nation’s 75,000 large dams. Many dams continue to serve public or private functions such as flood control, irrigation, and hydropower generation.” But for dams that have a clear and devastating effect on the environment, their removal helps restore riparian habitat. The report said of dam removal: “Dams all across the country have been or are in the process of being removed for three primary reasons: environmental, safety, and economic. Most removal decisions involve a combination of all three of these reasons.” Thousands of small dams remain in the United States in areas that at one time supported farming or logging.
Proponents and opponents have come to an uneasy truce regarding hydroelectric dams, meaning dams that produce electricity. Hydroelectric power replaces the need for coal-burning power plants, so these dams receive support from many people in the public and in government. John Doolittle, who served in the California House of Representatives
during the time a dam was planned for the town of Auburn, stated in 2006, “Any dam will eventually pay for itself. If you build a multipurpose dam, it’s a moneymaking machine because it generates the sale of electricity and of water.” At present, people continue to weigh the advantages of dams against the disadvantages. The sidebar “Three Gorges Dam” explores one of the world’s most famous and controversial dam projects.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
Dams provide benefits in water management in the following ways: (1) They conserve water by storing it in reservoirs; (2) they supply irrigation water; and (3) they reduce flooding downstream. In addition, many dams have been built for the main purpose of producing electricity. All of these factors have helped preserve people’s property, and the waterpower from dams serves as a sustainable energy source.
Dams conserve water in two ways: Reservoir water behind dams serves as low-cost storage for a community’s drinking supply, and the downstream flow provides a constant source of irrigation water. Both situations conserve groundwater. Lakes behind dams provide outdoor recreation areas and places for fishing, perhaps sparing wilderness areas from excess human activities. For each of these positives, however, there is also a disadvantage, summarized in the table below.
When dams interfere with natural water flows, they affect aquatic ecosystems that live in riparian habitats. Dams do this by changing the normal flow of sediments that carry nutrients to microbes and invertebrates, taking away long stretches of running water that some migrating fish need, and slowing water flow enough to allow salt water from estuaries to move upstream. Salt water contamination kills the diverse microbes, invertebrates, amphibians, fish, and plants that need freshwater.
Two opposing schools of thought have grown regarding the role of dams in the environment today, and not surprisingly, the arguments become contentious. Butch Hopkins of California’s Reclamation Board explained the major issue swirling around the American River’s Auburn Dam to the Sacramento Bee in 2006: “The dam is incredibly controversial because it runs flat into the fundamental beliefs of fiscal conservatives and environmentalists.” Those words describe almost all large dam projects in place today.
Dams allow communities to take advantage of a renewable energy source while they also practice water conservation. But environmentalists have called for the removal of large and small dams, and in the past few decades many dams have in fact come down, either because they had become dangerously degraded or because they were part of a riparian restoration. Three environmental groups—Friends of the Earth, Trout Unlimited, and American Rivers—published a report together in 1999 that detailed case studies of dam removal projects. Dam Removal Success Stories summarized the rationale behind dam removal: “Even for some functioning dams, removal may be a sound solution when a dam’s benefits are outweighed by the significant environmental damage it causes. . . . Clearly dam removal is not appropriate for all—or even most—of the nation’s 75,000 large dams. Many dams continue to serve public or private functions such as flood control, irrigation, and hydropower generation.” But for dams that have a clear and devastating effect on the environment, their removal helps restore riparian habitat. The report said of dam removal: “Dams all across the country have been or are in the process of being removed for three primary reasons: environmental, safety, and economic. Most removal decisions involve a combination of all three of these reasons.” Thousands of small dams remain in the United States in areas that at one time supported farming or logging.
Proponents and opponents have come to an uneasy truce regarding hydroelectric dams, meaning dams that produce electricity. Hydroelectric power replaces the need for coal-burning power plants, so these dams receive support from many people in the public and in government. John Doolittle, who served in the California House of Representatives
during the time a dam was planned for the town of Auburn, stated in 2006, “Any dam will eventually pay for itself. If you build a multipurpose dam, it’s a moneymaking machine because it generates the sale of electricity and of water.” At present, people continue to weigh the advantages of dams against the disadvantages. The sidebar “Three Gorges Dam” explores one of the world’s most famous and controversial dam projects.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
2012年5月4日
Salmon
The general names salmon and trout represent a number of different fish species that are born in freshwater, migrate to the ocean to mature, and then migrate back to inland freshwaters to reproduce. This migration is called a salmon run. Reproduction consists of a female laying eggs in a streambed’s gravel, the male fertilizing the eggs, and then the development of young fish; the entire process is called spawning.
Salmon populations exist in the Atlantic Ocean, the Pacific Ocean, and some large lakes, but all salmon populations have undergone declines over the past century, possibly due to altered habitat and overfishing. (When fewer salmon migrate in freshwater rivers and streams, bears, river otters, mink, and eagles are threatened because salmon make up a large portion of their diet and protein needs.) Most salmon species are fall spawners, meaning they travel hundreds of miles upstream from the ocean in time to spawn in the fall. The young stay at the spawning site for up to two years before heading to the ocean in the spring. Because each generation of salmon depends on safe, clean, flowing rivers and streams, riparian destruction has been endangering salmon for several years. Salmon runs in the Pacific Northwest have declined to 1–3 percent of the levels they attained when Lewis and Clark visited in the early 1800s.
Ideal riparian habitat for salmon consists of the following factors: year-round flow of cool (below 68°F, 20°C), clear water; streams with pools and riffles; clean and exposed spawning gravel; stable stream banks; dense shade canopy from trees; a supply of small branches fallen from trees; adequate supply of insects to eat; and an abundance of hiding places. Hiding places include shade-covered pools, rocky nooks, overhanging vegetation, and stationary tree branches, leaves, or other plant debris. Riparian destruction affects many of these vital factors. Even riparian habitats that people think are well maintained may be the biggest threat to salmon. Cutting down trees and clearing out overhanging vegetation allows more sunlight to warm the waters where salmon migrate. These warmer waters interfere with the normal physiology of adults and the survival of the young.
Scientists have begun to track Pacific salmon populations to assess the threats to the fish’s survival. To do this they catch salmon with nets at the river’s mouth and gently push a transmitter that holds an antenna into the fish’s stomach. This method has been used in the Oregon Rogue River Spring Chinook Conservation Plan. Since the Rogue River was dammed in the 1970s, yearly runs of chinook salmon fell from 28,000 on average to 9,000 in 1990 and fewer than 3,000 today. The scientist Tom Satterthwaite explained in 2008, “Results from this year will tell us how best to capture and tag fish, and most importantly, the minimum number of fish that need to be tagged to get statistically reliable results. We need to know this number because successful upstream migration of tagged chinook in other rivers varies from 30 percent to 90 percent, and in the Rogue, these fish face added stress from high summer water temperatures.” These studies may help explain the reasons behind salmon losses in the past several decades.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
Salmon populations exist in the Atlantic Ocean, the Pacific Ocean, and some large lakes, but all salmon populations have undergone declines over the past century, possibly due to altered habitat and overfishing. (When fewer salmon migrate in freshwater rivers and streams, bears, river otters, mink, and eagles are threatened because salmon make up a large portion of their diet and protein needs.) Most salmon species are fall spawners, meaning they travel hundreds of miles upstream from the ocean in time to spawn in the fall. The young stay at the spawning site for up to two years before heading to the ocean in the spring. Because each generation of salmon depends on safe, clean, flowing rivers and streams, riparian destruction has been endangering salmon for several years. Salmon runs in the Pacific Northwest have declined to 1–3 percent of the levels they attained when Lewis and Clark visited in the early 1800s.
Ideal riparian habitat for salmon consists of the following factors: year-round flow of cool (below 68°F, 20°C), clear water; streams with pools and riffles; clean and exposed spawning gravel; stable stream banks; dense shade canopy from trees; a supply of small branches fallen from trees; adequate supply of insects to eat; and an abundance of hiding places. Hiding places include shade-covered pools, rocky nooks, overhanging vegetation, and stationary tree branches, leaves, or other plant debris. Riparian destruction affects many of these vital factors. Even riparian habitats that people think are well maintained may be the biggest threat to salmon. Cutting down trees and clearing out overhanging vegetation allows more sunlight to warm the waters where salmon migrate. These warmer waters interfere with the normal physiology of adults and the survival of the young.
Scientists have begun to track Pacific salmon populations to assess the threats to the fish’s survival. To do this they catch salmon with nets at the river’s mouth and gently push a transmitter that holds an antenna into the fish’s stomach. This method has been used in the Oregon Rogue River Spring Chinook Conservation Plan. Since the Rogue River was dammed in the 1970s, yearly runs of chinook salmon fell from 28,000 on average to 9,000 in 1990 and fewer than 3,000 today. The scientist Tom Satterthwaite explained in 2008, “Results from this year will tell us how best to capture and tag fish, and most importantly, the minimum number of fish that need to be tagged to get statistically reliable results. We need to know this number because successful upstream migration of tagged chinook in other rivers varies from 30 percent to 90 percent, and in the Rogue, these fish face added stress from high summer water temperatures.” These studies may help explain the reasons behind salmon losses in the past several decades.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
2012年5月1日
Threats to Waterways
Waterway pollution threatens the health of the biota that depend on aquatic habitat and the people that depend on the waterway as a drinking water source. In developing regions, chemical pollution and sewage have created a serious threat to both habitat and people. More than half of the rivers in India, Africa, and Latin America contain heavy pollution, but the greatest problem may be in China, where most of the coasts, rivers, canals, and lakes contain industrial pollutants. Hundreds of thousands of people in China turn to bottled water because no other safe water source exists, but the wildlife living in these areas have no choice but to ingest contaminated water. China’s Ministry of Environmental Protection has waged a war on the pollution problem and has managed to control some of the pollution, but waterway pollution remains a problem that industries have not yet addressed. The Beijing environmentalist Ma Jun told the New York Times in 2008, “We need to have an understanding that this is just the turning point in pollution discharges; this isn’t the turning point in the environment.” Waterway pollution control remains an enormous obstacle to a healthier environment in China and other nations.
The main sources of river pollution worldwide are sewage, effluent from livestock farms, manufacturing and industrial discharges, mining wastes, materials from housing and road construction, and the myriad wastes carried in rain runoff, including gasoline and oil. Urbanization adds its own mixture of eroded soil, solid wastes, rubbish, and organic matter. The relative amounts of these pollutants differ between developed and developing countries, but each of these pollutants represents worldwide problems in riparian health.
Four factors cause riparian destruction in addition to pollution: physical alterations; destruction of catchment areas; mismanagement of fish resources; and invasive species. Physical alterations include structures built into or near waterways for the purpose of flood control, landscaping, or power generation. Some urban centers alter waterways simply because the city wants the water to pass through it in a more convenient way. Altering riparian areas is not confined to large cities, as a Glenwood Springs, Colorado, resident pointed out in a 2008 letter to the Glenwood Springs Post Independent: “There are large subdivisions all over the [Roaring Fork] Valley where the prime riparian has been ripped up entirely to support exclusive subdivisions, malls and golf courses. . . . I don’t find golf courses, shopping centers and parking lots a positive addition to the environment. All that manicured green grass, asphalt and chemical warfare has replaced the oak brush, sagebrush and the natural habitat. The irony is the new pavement is named Heron Circle, Eagle Court, Hawk Lane, yet we’ve destroyed the birds’ actual habitat.” Construction that was once well-meaning has turned into a hazard for habitat and biodiversity.
Some of the major restructuring projects that have been completed on rivers and streams that cause major impact on riparian environments are the following:
» dams for flood control, drinking water reservoirs, or power generation
» clearing of riparian vegetation for landscaping
» constructed channelization through urban areas
» river diversion in urban areas
» deepening, straightening, or widening rivers for ship use
» docks and boardwalks for recreation
Physical alterations change waterways’ normal routes, sediment settling, water temperature, and water chemistry. All these factors affect biota from microbes to old-growth trees that live in the catchment area. Catchments consist of mountain lakes, ponds, and streams as well as the moisture stored in trees and soil. New developments on mountaintops that cut down trees and landscape the area for roads and views change the catchment’s capacity to store water for later use downstream. Clear-cutting, mining, and agriculture impose similar effects on catchments.
Mismanagement of fish resources in natural rivers and streams also damages riparian habitat. Illegal fishing, overharvesting, or fishing without regard for the environment affects these habitats as does the use of poisons, nets, and even explosives. Other ills brought by irresponsible fishing are the waste pollution and overuse of the same riparian location. Overuse causes three main damages to the riparian habitat: destroyed terrain; trampled vegetation on the banks; and alteration of wildlife’s normal patterns.
Riparian habitats also receive damage from invasive vines or bushes that people plant along waterways. These plants have the potential to displace native vegetation that serves as food, shelter, and nesting sites for wildlife. Invasive fish species also alter the natural ecosystem in ways that may affect biota far downstream, particularly by interfering with normal food chains.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
The main sources of river pollution worldwide are sewage, effluent from livestock farms, manufacturing and industrial discharges, mining wastes, materials from housing and road construction, and the myriad wastes carried in rain runoff, including gasoline and oil. Urbanization adds its own mixture of eroded soil, solid wastes, rubbish, and organic matter. The relative amounts of these pollutants differ between developed and developing countries, but each of these pollutants represents worldwide problems in riparian health.
Four factors cause riparian destruction in addition to pollution: physical alterations; destruction of catchment areas; mismanagement of fish resources; and invasive species. Physical alterations include structures built into or near waterways for the purpose of flood control, landscaping, or power generation. Some urban centers alter waterways simply because the city wants the water to pass through it in a more convenient way. Altering riparian areas is not confined to large cities, as a Glenwood Springs, Colorado, resident pointed out in a 2008 letter to the Glenwood Springs Post Independent: “There are large subdivisions all over the [Roaring Fork] Valley where the prime riparian has been ripped up entirely to support exclusive subdivisions, malls and golf courses. . . . I don’t find golf courses, shopping centers and parking lots a positive addition to the environment. All that manicured green grass, asphalt and chemical warfare has replaced the oak brush, sagebrush and the natural habitat. The irony is the new pavement is named Heron Circle, Eagle Court, Hawk Lane, yet we’ve destroyed the birds’ actual habitat.” Construction that was once well-meaning has turned into a hazard for habitat and biodiversity.
Some of the major restructuring projects that have been completed on rivers and streams that cause major impact on riparian environments are the following:
» dams for flood control, drinking water reservoirs, or power generation
» clearing of riparian vegetation for landscaping
» constructed channelization through urban areas
» river diversion in urban areas
» deepening, straightening, or widening rivers for ship use
» docks and boardwalks for recreation
Physical alterations change waterways’ normal routes, sediment settling, water temperature, and water chemistry. All these factors affect biota from microbes to old-growth trees that live in the catchment area. Catchments consist of mountain lakes, ponds, and streams as well as the moisture stored in trees and soil. New developments on mountaintops that cut down trees and landscape the area for roads and views change the catchment’s capacity to store water for later use downstream. Clear-cutting, mining, and agriculture impose similar effects on catchments.
Mismanagement of fish resources in natural rivers and streams also damages riparian habitat. Illegal fishing, overharvesting, or fishing without regard for the environment affects these habitats as does the use of poisons, nets, and even explosives. Other ills brought by irresponsible fishing are the waste pollution and overuse of the same riparian location. Overuse causes three main damages to the riparian habitat: destroyed terrain; trampled vegetation on the banks; and alteration of wildlife’s normal patterns.
Riparian habitats also receive damage from invasive vines or bushes that people plant along waterways. These plants have the potential to displace native vegetation that serves as food, shelter, and nesting sites for wildlife. Invasive fish species also alter the natural ecosystem in ways that may affect biota far downstream, particularly by interfering with normal food chains.
Source of Information : Green Technology Conservation Protecting Our Plant Resources
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