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# Human Causes of Extinction

## Describes human-caused problems that are threatening many species.

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Invasive Species
teacher Contributed

Source: Video Journalism Movement (www.vjmovement.com) in The Netherlands

becoming an invasive species


All species are important and necessary for the survival of the ecosystem but sometimes when some species are introduced to a foreign environment, then it will be a different story.

Invasive Species
can harm both the natural resources in an ecosystem as well as threaten human use of these resources.

### How Can An Organism Become Invasive?

#### 1.  Introduction to a new area:

• via the ballast water of oceangoing ships
• intentional and accidental releases of aquaculture species
• aquarium specimens
• bait
• hurricanes, typhoons, tsunamis
• and other means:
• Globalization:  Global trade has become the single largest factor in the worldwide spread of invasive species by means of ships, planes, and railroads (Bright 1999).
• Climate Change:  Invasive species are also closely connected with climate change. Biological changes caused by heightened levels of carbon dioxide and variations in temperature and precipitation patterns will have major impacts on the distribution and population levels of species, in addition to the composition and relationships between species in ecosystems (Chornesky and Randall 2003).

### What Are The Roles Of The Invasive Species?

1. Invasive species are capable of causing extinctions of native plants and animals
2. reducing biodiversity
3. competing with native organisms for limited resources
4. and altering habitats

### Environmental Impacts

1. The introduction of invasive species can result in the extinction of local species and irreparable changes to the habitat and biodiversity of invaded ecosystems (Chornesky and Randall 2003).
2. These species lead to the killing or crowding out of native species through predation, parasitism, disease, and competition (Chornesky and Randall 2003).
3. They also alter ecological processes such as the water, nutrient, and energy cycles, thus completely changing how ecosystems function (Union of Concerned Scientists 2007).
4. Invasive and native species can mate to form hybrid species, which can potentially displace the native species, leading to a loss of stability among the native population and eventual extinction (Cleeland and Mooney 2001).

### Economic Impacts

1. The economic impact of invasive species is derived from direct and indirect costs.
• Direct costs are those related to controlling the spread of invasive species, such as the use of pesticides applied in an attempt to contain the spread of pests.
• Indirect costs relate to billions of dollars are spent annually as a result of invasive species (Invasive Species Specialist Group 2007).

### Health Impacts

1. Invasive species spread disease that can be devastating to human health (National Environmental Coalition on Invasive Species 2004).
2. Increased transportation and accessibility have allowed for new interaction between diseases and human hosts.
3. Many non-native species can act as reservoirs for disease, including insects, rodents, and birds, which carry diseases such as yellow fever and malaria.
4. Invasive species include food security and water depletion, which are significant concerns in developing countries (Global Invasive Species Program 2007).