Chapter 6
According to Marris, an invasive species is an organism that moves into a new ecosystem where it “naturalizes,” and reproduces to the extent that it becomes a nuisance to the native species by taking over the existing resources needed for survival by the other species. An invasive species, is usually associated with negative environmental, social, o health impacts, and is always believed to outcompete the previously existing organisms. Marris lists various species that are considered invasive including kudzu, also referred to as “the weed that ate the south” and zebra mussels that hog planktons found in lakes. Along the York River, Phragmites are being eradicated; the Nation Park Service team has always attempted to get rid of the species since 2000 claiming that it is an invasive species. The attempts have been made using herbicides in order to completely destroy their existence.
Charles Elton considers invasive species existence a natural “niche” process, and as such should not be associated with environmental degradation. According to him, an ecosystem contains different organisms with variable roles or niches, and most often every role is filled with particular organisms. In the food chain, he asserts, some will be feeding on leaves while others on grass. By introducing an invasive species to an environment, the species can only survive if it gets a vacant niche or displacing other species that are not fit to survive. Since he observe co-existence among species to be possible like in the case of chestnut blight fungus and Asian native trees, the concept of native species should not be associated with negative impacts.
No. Not all invasive species are harmful to the environment. In fact, Marris highlights various invasive species that have benefited the ecosystem. For instance, she gives Davis’ example of the squidgy brown sea-squirt-like creature, Pyura praeputialis, in Australia which has increased biodiversity existence in the Chilean shores. Another example is the case of the blue tits in Britain; being on the verge of extinction as a result of starvation, an invasive species, Turkey oaks, appeared in the area and acted as source of food, thus, aiding in the birds’ survival.
Chapter 7
A novel ecosystem refers to a combination of exotic species which perform ecosystem functions just like the native species, and may be able to provide humans with the necessary natural resources and services including carbon cycle, carbon sequestration, water filtration, habitat for rare species, and cultural benefits. An example of such ecosystem is that studied by Mascaro, the pinelike Australian ironwood. The ecosystem is dense with liter undergrowth as well as variety of ferns from India, the single silk oak, and different tree species including the trumpet tree.
While managing a crew of researchers who measured the ground cover of pine plantation, Ariel Lugo discovered that novel ecosystems can perform better than the native ecosystems. After years had passed and the crew went back to the forest, Ariel realized diverse changes that were very significant. Compared to the adjascent native ecosystem, this pine plantation was “packed with living things.” There were various flora and fauna species that flourished in the area. Unlike the feral mahogany ecosystem, the novel ecosystem had a richer understory with great amount of biomass, utilized nutrients efficiently, and functioned better than the native.
While at the “mango forest,” Mascaro showed the author a novel ecosystem composed of diverse exotic species. She saw mango trees that have grown into “huge, vulnerable specimens with their fruits impossibly high off the ground.” There were trees of different heights and sizes, with crows of mango seedlings jostling for light. Apart from other species that lived on the tree branches, including basket fan, they also observed variety of rare species lie trumpet tree and strawberry guava.
Erle Ellis who is a professor at the University of Maryland illustrates the amount of novel ecosystems on Earth. He believes that most of these ecosystems are created by humans who interfere with the natural ecosystem. According to Ellis, trees exist as a result of human existence within the landscape, and as such classifies land by using terms such as “dense settlement, rice villages, and populated irrigated cropland.” He discovered that more than 75% of land had been altered by human existence with only 22% of rangeland remaining absolute pristine.
Chapter 8
In this chapter, Robert Walter and Dorothy Merritts found out that the streams in the Piedmont region of US had changed in their structure. They were morel like swamps as water run in multiple streams, got tracked in pools, and collected mud which spread into valley floors. In the 18th century, instead of the streams running in single streams, they spread out and formed dams which later turned into millponds. Due to the increase in deforestation and land clearance, water supply and inflow of soil to the millponds increased, thus causing deposition of sediments. This in turn resulted in the breaching of the dams, causing a burst in fast flowing water cutting through the channels that currently people assume are “natural.”
Margaret Palmer highlights various conflicts regarding environmental restoration. One of the conflicting beliefs is that historical baseline is the most ideal for restoring the stream features and other systems that had been lost over the years. Palmer explains that such a notion is fallacy since no one knows how the systems existed in the past, and that a lot has changed including anthropogenic activities and the nature of the environment. The author also identifies the lack of human’s capability to restore nature. She claims that restoration would require people to buy and protect areas of currently valuable ecosystem.
Designer ecosystems are the previously depleted or changed ecosystems that are reconstructed or “redesigned” in order to return them to a stable “natural” state. To illustrate this kind of ecosystem, Marris gives an example of a failed restoration attempts in Colorado which resulted in the creation of a new ecosystem of grass that is dominated by Sporobolus airoides. Timothy Seastedt commented that the designer ecosystem seems desirable to the locals.
In the last two paragraphs, Marris admits that both restoration and designing are fundamental aspects of ecosystem management. She suggests that designers like Dubos believe that creating ecological systems will enable both nature and humans to co-exist. On the other hand, ecologists believe restoration is important, that part of natural land should be left fallow just to observe species regenerate as in the past. As such, Marris suggests that there is need to conduct both conservation techniques, keeping the wilderness (restoration of parks) and redesigning the existing natural environment to accommodate human needs and the biodiversity.
Chapter 9
Habitat fragments are the small and partitioned protected areas which are aimed at enhancing biodiversity conservation. An example is a park which harbors a limited number of species; the fact that it is separated from other conservation areas hinders diversity of species, and instead result in leaking and loss of organisms. An example of a habitat fragment that Marris highlights is the Yellowstone National Park which is 3,500 square miles. Because it is just a fragment, the species like grizzly bear who depend on the habitat cannot be contained especially when the population rises. Corridors are created to unite such habitat fragments in order to create a link between the different ecosystems, thus, creating more interconnected ecosystem that enhances survival of species and biodiversity. An example of a corridor that has enhanced diversity in ecosystem is the Mesoamerican Biological Corridor which unites Mexico and Central American protected areas. The long path creates way for antelope species to move near Yellowstone.
Farms can act as a form of conservation if proper practices are embraced. According to Marris, farmers who avoid subdivision of land, and instead consider activities that would encourage environmental conservation can easily enhance biodiversity conservation. An example illustrated is the United Kingdom where farms are used to rear birds through the “farmland birds” programs. This farming technique has been adopted by many of the Europeans, and has helped to reduce intensified farming, monoculture, and overgrazing.
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