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Research paper topic: Tropical Rainforests Of The World - 2795 words
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.. racterized as a nest parasite because it because it replaces the eggs of another species with eggs of their own , allowing the other species to incubate and raise their young. Their increased numbers have had negative effects on the reproductive successfulness of many forest-dwelling birds. In addition to titling the ecosystem balance in favor of species which are highly adaptable, the loss of habitat associated with habitat fragmentation may simply cause the other, less adaptable species rates to decline. A man named James Saunders documents one remarkable example of how changing large expansive areas of the birds of the wheatbelt of western Australlia as a result of fragmentation.
He showed that 41% of the birds native to the region have decreased in range or abundance since the 1900s and indicated that almost all of these changes resulted directly from habitat fragmentation and the decline in abundance of native vegetation. Although some species have increased in abundance, he noted that many more species have been adversely affected than have benefited. Importantly, the species that typically increase in abundance or range when habit fragmentation occurs are those which are adapted for being adaptable. In other words, their resource needs can be met by a variety of conditions, and thus often by human activities by reducing their competition with other species. Because of this, these species which benefit by human activities are not the ones we need to manage for and protect. Instead, we need to protect those species which are adapted solely for survival in the rapidly disappearing unfragmented habitat. Besides physically changing a part of the original habitat, decreasing the size of the original habitat can reduce the biological diversity of an area in several ways.
Reducing biodiversity of an area may occur if habitat fragments are smaller than the home range of the animal with the largest home range that existed within the intact ecosystem. Many birds have large home ranges because they require patchily distributed resources. For example, one breeding pair of ivory billed woodpeckers require five to six square miles of undisturbed contiguous bottomland forest, and a single European goshawk requires twenty to forty-five miles for his home range. If a habitat fragment exists that is smaller than the minimum area required by a given species, individuals of that species will not likely be found within that habitat fragment. For example, the Louisiana waterthrush is rarely found in small woodlots because they require open water within their home range, and most small woodlots do not have year-round streams or ponds.
If a species requires two or more habitat types, they are often susceptible to local extinction due to habitat fragmentation, because often they are unable to freely move between the different habitat types. The blue-grey gnathatcher moves from decidous woodland to chapparral (a warm area) during the breeding season, and if one of the two habitat types can not be readily accesed, they are very susceptable to local extinction. Loss of any species from a community may have secondary effects that revrberate throughout the ecosystem. For example, loss of a top predator from an area because the fragment is too small can cause numbers of small omnivores to increase, which in turn may cause excessive predation pressureon songbird eggs and hatchlings, ultimately resulting in reproductive sucess. Tropical communities are oftem more susceptable to loss of biological diversity than temperate communuities, because tropical species typically are found in lower densities, are less widely distributed, and often have weaker dispersal capabilities. Many tropical species have evolved in that they have changed their roles that they play in the rainforest. An example of this occurance is the cassowary, an Austrailan rainforest frugivore, (or an animal that primarily feeds on fruit) is extremely susceptable to local extinction by habitat fragmentation because its habitat requirement of large coniguous rainforest areas is compounded by its unique plant-seed despersal evolvment.
This large, flightless bird wanders nomadically in search of very large seeds, many of which need to be digested before they will germanate. Youlll rember that earlier another example of this situation in which the dodo bird became extinct. The dodo bird digested seeds of the calvaria tree. But when the dodo bird became extinct due to overhunting by humans, the calvaria tree, which made the seeds to be digested by the dodo bird to sprout its plants started not to sprout seeds. In the Rainforests, their are many such instances like this. But unfortunately, many of them go unnoticed and thus, each day many of the rainforest plants and animals go extinct. Besides being home to extinction-prone species, tropical communities are prone to destruction and fragmentation because of their physical location, overlapping with the geographical birders of the third world nations.
In these nations, citizens often rely on the revenues raised from rainforest timber or cattle raised on cleared land for survival. This constant pressure on rainforest communities leads to excessive habitat fragmentation. Small isolated fragments result, leading to an altered ecosystem balance. On the tropical island of Java, where almost all of the original habitat remaining exists in reserves, a group of ecologists have assessed the status of all of the birds of prey found in the rainforest habitat. Nearly all the raptors were extremely rare outside the reserves, as expected.
They also found that the larger the reserve was, the denser the birds populations were within the reserve. Interestingly, a scientist named Lovejoy (I couldnt find his first name) in 1986 found a similar phenomena with Amazonian birds in the Biological Dynamics of forest project (BDFF) in Brazil. The primary goal of the project is to discover how rainforest communities respond after an intact ecosystem is split into different size fragments. They found a crowding effect, in which the abundance of birds in a forest fragment increased significantly directly after deforestation of the adjacent area. The increased number of birds was attributed to the migration of birds from the newly clear-cut area to the forest fragment. This crowding effect decreased with increasing size of a forest fragment.
Both tropical and temperate communities, however, are prone to the same problems of inbreeding and loss of genetic variability, which results from isolating subpopulations of plants and animals from each other due to habitat fragmentation. If too large a distance exists between two fragments and a species are unable to disperse across the area in between, the population is essentially divided. Inbreeding may result if the subpopulation in a given fragment is small. This has not been directly documented, but it is possible. Size of a fragment and the amount of edge are inextricably linked.
Abrupt edges often results form fragmenting and ecosystem, in contrast to the more gradual natural ecotones. Edge positively impacts many species of plants and animals, but as mentioned previously, the species which benefit typically are those which do not require human protection and management because they can easily meet their resource need outside of the intact ecosystem. The scientists from the BDFF project point out one exception. Tamarins and marmosets, both species in need of protection , flourish in small tropical rainforest reserves because of the luxurian growth of early successional plant species, and the lack of large predators which are unable to exist in the smaller reserves. Certainly , a system of only small reserves would not suffice to protect the genetic heritage of biological diversity in the tropical rainforest, but a heterogeneous mosaic of large and small reserves may provide the best alternative. Although edge has typically been associated with an increase in species richness, researchers are increasingly documenting how edge effects negatively impact the native plants and animals.
The BDFF researchers pointed out that although the number of species may be higher in edge that the adjacent interior habitat, species diversity is usually not. Diversity takes into account not only raw number of species, but the relative abundance of the species present. Another potentially adverse effect of edge is that it inherently reduces the size of the habitat interior because of the many physical changes which occur where and edge is compared to a human dominated area. Most documented cases of edge effects are from forest edges, so I will focus on them. In addition to the luxuriant growth of shade-intolerant vegetation at a forest edge in response to the increase in available light, a seed rain bombards the forest interior, often from introduced exotics.
The increased exposure to wind causes a higher rate of treefalls and tree mortality, and temperature and humidity are quite different at the edge than in the forest interior. These physical changes affect the plants and animals of the habitat. Lovejoy and others, in the BDFF project in Brazil, found that the understory birds tend to avoid artificial edges. They found 38% fewer birds 10 meters from clearing than 50 meters into the forest, and 60% fewer birds 10 meters from a clearing than 1 km into undisturbed forest. An interesting item is that they did not find a lower abundance of birds around natural edges, such as interior treefall gaps. Several authors that I have read have suggested that the abundance of birds decreases near an artificial edge due to decreased Nest success.
Nest success near edge decreased because of the increase in generalist predators and brood parasites. As mentioned earlier, populations of brown-headed cowbirds, a brood parasite, have increased tremendously as a direct result of human activity, these birds have a negative impact on the nesting success of forest songbirds that nest near the forest edge. Studies show that while vegetational changes may extend from 300-600 meters into a fragment. This makes sense when one considers that although generalist predators such as raccoons, cowbirds, and chipmunks may concentrate their activity near the edge, they certainly also can frequent the forest interior, often to the damage of those species which rely exclusively on forest interior. To reduce how far edge effects penetrate into a natural habitat, a biologist Bernard Harris, proposed a system of long-rotation islands, in which and old-growth center is surrounded by various age stands of timber.
This system provides some edge for those species which benefit from it, while minimizing the amount of edge between the old-growth center stand and the surrounding stands. Now, to the final section of this term paper, the role that environmentalists play and some of the reasons that they are trying to save it. Rainforests cover less that two percent of the Earths surface, yet they are home to some 40 to 50 percent of all life forms on our planet, as many as 30 million species of plants, animals, and insects. The Rainforests are quite simply, the richest, oldest, most productive, and most complex ecosystems on Earth. As biologist Norman Meyers notes, Rainforests are the finest celebration of nature as ever known on the planet, and never before has natures greatest orchestration been so threatned.(4) His quote is quite true.
The following facts listed are direct proof of how the Tropical Rainforests are being depleted. Global Rates of Destruction 2.4 acres per second: equivalent to two U.S. football fields 149 acres per minute 214,000 acres per day: an area larger than New York City 78 million acres per year: an area larger than Poland In Brazil 5.4 million acres per year 6-9 million indigenous people inhabited the Brazilian rainforest in 1500. In 1992, less than 200,000 Species Extinction Distinguished scientists estimate and average of 137 species of life forms are driven into extinction every day or 50,000 each year. While you were reading the above statistics, approximately 90 acres of rainforest were destroyed. Within the next hour approximately six species will become extinct.
While extinction is a natural process, the alarming rate of extinction today, comparable only to the extinction of the dinosaurs, is specifically human-induced and unpreceeded. Experts agree that the number one cause of extinction is habitat destruction. Quite simply, when habitat is reduced, species disappear. In the Rainforests, logging, cattle ranching, mining, oil extraction, and hydroelectric dams all contribute to rainforest destruction and produce many undesired effects in the environment such as global warming, depletion of the ozone layer, and depletion of the earths natural resources. But now, there may be some help for the rainforest.
Until recently, few vacationers would even dream of visiting a rainforest. But travelers are now abandoning the traditional beach vacation to visit remote, unspoiled areas all over the world. They try to avoid the fast pace and congestion of the traditional tourist centers, opting instead for more adventure, stimulation and a desire to learn while on vacation. This growing trend of travel has come to be known as ecotourism. Though there are many definitions of ecotourism, the term is most commonly used to describe any recreation in natural surroundings.
The Ecotourism Society adds social responsibilities to define ecotourism as purposeful travel to natural areas to understand the culture and natural history of the environment, taking care not to alter the integrity of the ecosystem, while producing economic opportunities that make the conservation of natural resources beneficial to local people(5) However defined, ecotourism is a force shaping the use of the tropical Rainforests. This will be even more true in the future due to ecotourisms rapid growth. Global tourism is one of the largest industry in the world and ecotourism is the fastest growing segment of the industry. Tourism is largely responsible for saving the gorillas of Rwanda from extinction. The gorilla was threatened by both poachers and local farmer, whose land clearing practices were destroying the gorillas natural habitat.
Rwandas Parc des Volcans, created by Dian Fossey as a wildlife preserve, has become an international attraction and the third largest source of foreign exchange for Rwanda. Revenues from the $170-a-day fee that visitors will pay to enter the park have allowed the government to create anti-poaching patrols and employ local farmers as park guides and guards. Even this success is danger from the civil war that is encroaching and endangering both the forest and tourist industry. If ecotourism is going to be influential in saving Rainforests, income from tourism must reach the people who will ultimately decide the forests future. Unfortunately, too often the money generated does not benefit these people.
Instead, it goes to developed countries, where the tourists originated, giving little economic protection to the forests. Profits leak back to the developed nations through tour operators, plane tickets, foreign owned accommodations and use of non-local supplies. The World Bank estimates that worldwide only 45 percent of tourisms revenue reaches the host country. In less developed areas, the percentage is often lower. One study of the popular ecotourism destination of the Annapurna region of Nepal found that only 10 cents of every dollar spent stayed on the local economy.
Within the country, the money may end up in the large cities of in the hands of the wealthy elite. Tourist dollars should help to acquire and improve management of conservation areas on which the tourism is based, but money from tourism does not often end up with the agencies that manage these areas. In Costa Rica, the park service does not earn enough money from its entrance fees to manage and protect its numerous parks. Only 25% of its budget comes from fees; the other three quarters must come from donations. Tourists often resent paying large sums of money on entrance fees. Although these fees are only a small portion of the money spent on a trip they can be the most important dollars spent in protecting the resource because they go directly toward protecting the site.
The environmentalists and government officials play a vital part in the protection of the Rainforests. Without them, all of the Rainforests would probably be gone. (4) In conclusion, the Rainforests, the lungs of the earth will be gone in just a few years if the current rates of destruction continue. But luckily, there are environmentalists there to protect the rainforest and potentially protecting our lives. I say protecting our lives because in the past 100 years the earths temperature has risen one degree Fahrenheit.
This may sound small and insignificant but it is very serious. Combined with global pollution from cars, factories, etc. the depletion of the Rainforest has caused the level of the earths air quality to lower, more arctic icebergs to melt causing water levels to rise around the world causing more erosion and nameless other effects. If within 20 years, more is not being done estimates the rainforest action network, our earth will begin to change into a hot planet, flaming with CO2, with clouds made up of sulfuric acid, much like the planet Venus. (11) These factors, in the advanced stage of Global Warming are what the earth is coming to if something is not being done soon about the destruction of the tropical Rainforests and various other types of pollution. The earth will become a death trap for the human race unless we act now!.
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