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E10. Human practices can lead to major changes in communities.




Student Outcome: E10.1

Give examples of species’ extinctions that have been brought about by human activities.


  • Example: Ballast Water


Ballast water is carried in unladen ships to provide stability. It is taken on board at the port before the voyage begins and tiny stowaways, in the form of marine organisms, are taken on board with it.


During the voyage, temperature changes in the ballast water and lack of food and light kill many, but not all, of these organisms. At the ships' destination, the cargo is loaded and the ballast water, with its surviving stowaway organisms, is pumped out. Some of these organisms then establish populations in the surrounding waters.


Over 100 species of marine organisms are known to have been introduced by ballast water. While some appear benign, others have become pests, threatening biodiversity, fisheries and aquaculture. Some introduced species severely deplete native populations or deprive them of food. Others form colonies which can smother existing fauna. Introduced toxic dinoflagellates cause red tides and algal blooms that can affect or even kill shellfish, fish, sea birds and humans.


Source: http://www.amonline.net.au/factsheets/ballast.htm


  • Example: Bitou Bush


Bitou Bush, (Chrysanthemoides monilifera), is a native of South Africa. It was intentionally imported into Australia as early as 1858. However, it was also unintentionally imported, probably in the dumped ballast water of a South African ship.


Bitou Bush has only become a problem in Australia in the last few decades, since being used to stabilise coastal sand dunes after sand mining. In the absence of the South African organisms which usually feed on it, Bitou Bush has choked native Australian vegetation. In the early 1970s, it was discontinued from use but by then it was too late: Bitou Bush was firmly established along more than half of the coastline of New South Wales. Ironically, one of the plants being choked - Golden Wattle (Acacia longifolia) - has become a major pest of coastal dunes in South Africa, where it was introduced to serve much the same purpose as Bitou Bush in Australia.


Many groups of organisms are dependent on native vegetation and are not adapted to survive on Bitou Bush. To find out the effect Bitou Bush has on the diversity of native organisms, such as arthropods, scientists at the Australian Museum are studying the differences between areas which are infested with Bitou Bush and areas which still have native vegetation. Scientists at the Australian Museum are now also studying the effects of controlling Bitou Bush with herbicides. In recent years, the New South Wales Department of Agriculture has embarked on a campaign to control Bitou Bush by aerial spraying of herbicides from a helicopter. The herbicides kill the Bitou Bush but don't affect the native vegetation. However, the herbicide might be toxic to certain groups of animals, such as arthropods, and the spraying also causes dramatic short-term changes to the environment.


It is hoped that these studies will give us further insight into the effects of introduced species on native biodiversity, while also giving us an opportunity to assess our attempts to rectify the mistakes of the past.


Source: http://www.amonline.net.au/factsheets/bitou_bush.htm


The Red List - species that are endangered or facing extinction.

Polar bears and hippos have joined the ranks of species threatened with extinction from climate change, unregulated hunting and other dangers created by humans.


The International Union for the Conservation of Nature and Natural Resources said yesterday more than 16,000 species of animals and plants were at risk of disappearing, including one in four mammals and one in eight birds.


It added 530 species to its "Red List" of endangered species since the last version released two years ago.


It classified the polar bear as a "vulnerable" species, one step down from "endangered" in its ranking of extinction risk. The polar bear was previously called a less-severe "conservation dependent" species.


The common hippo was also ranked as vulnerable, "primarily because of a catastrophic decline in the Democratic Republic of Congo," the union said.


Australia, China, Brazil and Mexico are home to large numbers of threatened species, said the union, whose members include 81 governments, more than 850 non-governmental groups and about 10,000 scientists.


It urged countries to boost efforts to preserve biodiversity through reduced emissions, tighter fishing and hunting controls, and other measures.


Source: http://www.smh.com.au/news/world/extinction-threat-emergency-ward-for-16000-species/2006/05/02/1146335735399.html


This map shows the extent of human activity on the world. You can go to specific sites in the world to see the impact on specific animals. On the same site you can get an idea of the distribution of the world's population, distance to the closest road, etc. Go here.


Student Outcome: E10.2

Explain why the best way to preserve species is to preserve habitat.


Conserving biodiversity has not always been high on the conservation agenda. In the past, most conservation efforts were focussed on saving a particular species from decline or extinction. Many conservationists argued that this was an effective way to not only protect endangered species, but to conserve biodiversity as well. This was because protecting an endangered species usually involved protecting that species' habitat and therefore all the other plants and animals in that habitat gained protection as well. This argument has some merit, because it is usually easier to gain support for the protection of one particular species than it is to convince people to support the conservation of biodiversity as a whole.


However, we now know that this approach is not the best way to conserve biodiversity. Areas we protect for a single species are not necessarily the areas we would protect if we were primarily interested in conserving biodiversity. There are a several reasons for this:


  • If we only conserve areas because they are home to an endangered species, we may neglect some of the most important areas for biodiversity conservation.
  • One of the three levels of biodiversity is ecosystem diversity, which is unlikely to be preserved if we only assess areas for preservation based on a single species.
  • If we wait until a species is recognised as endangered before we preserve an ecosystem, the ecosystem may be so degraded that not only is the target species doomed but so are all the other unknown species that also inhabit that environment.
  • Most conservation of a single species focuses on vertebrates or flowering plants whereas invertebrates, non-flowering plants, fungi and micro-organisms, which make up the bulk of species diversity in any ecosystem, tend to be ignored.


If we are genuine in our desire to conserve biodiversity, it is far more efficient to conserve whole ecosystems which encompass biodiversity at all levels, rather than focus on a few highly visible and popular species in isolation.


Here is a very good explanation of biodiversity and how we are reducing it.


Source: http://www.amonline.net.au/factsheets/conserving_biodiversity.htm


Why Have Species Become Endangered?

Habitat Loss

Loss of habitat or the "native home" of a plant or animal is usually the most important cause of endangerment. Nearly all plants and animals require food, water, and shelter to survive, just as humans do. Humans are highly adaptable, however, and can produce or gather a wide variety of foods, store water, and create their own shelter from raw material or carry it on their backs in the form of clothing or tents. Other organisms cannot.

Some plants and animals are highly specialized in their habitat requirements. A specialized animal in North Dakota is the piping plover, a small shorebird which nests only on bare sand or gravel on islands of rivers or shorelines of alkali lakes. Such animals are much more likely to become endangered through habitat loss than a generalist like the mourning dove, which nests successfully on the ground or in trees in the country or city.

Some animals are dependent on more than one habitat type and need a variety of habitats near each other to survive. For example, many waterfowl depend on upland habitats for nest sites, and nearby wetlands for food supplies for themselves and their broods.

It must be emphasized that habitat does not have to be completely eliminated to lose its usefulness to an organism. For example, the removal of dead trees from a forest may leave the forest relatively intact, but eliminate certain woodpeckers that depend on dead trees for nest cavities.

The most serious habitat loss totally changes the habitat and renders it unfit for most of its original resident organisms. In some areas, the greatest changes come from plowing native grasslands, draining wetlands, and constructing flood-control reservoirs.


What Are The Solutions?

Habitat protection is the key to protecting our rare, threatened, and endangered species. A species cannot survive without a home. Our first priority in protecting a species is to ensure its habitat remains intact.

Habitat protection can be done in a variety of ways. Before we can protect a plant's or animal's habitat, we need to know where this habitat is found. The first step, then is to identify where these vanishing species are found. This is being accomplished today by state and federal agencies and conservation organizations.

Second to identification is planning for protection and management. How can the species and its habitat be best protected, and once protected, how can we make sure the species continues healthy in its protected home? Each species and habitat is different and must be planned on a case-by-case basis. A few protection and management efforts have proven effective for several species, however.

Legislation was passed to protect the most endangered species in the United States. These special species cannot be destroyed nor can their habitat be eliminated. They are marked in the endangered species list by an *. Several federal and state agencies are beginning to manage threatened and endangered species on public lands. Recognition of private landowners who have voluntarily agreed to protect rare plants and animals is underway. All these efforts need to continue and be expanded to keep our natural heritage alive.




Interested in helping out? Why not join the Green Corps next year?


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