Humans earn and secure their Livelihood by modification of the environment, driven by demands for water, food, and energy.
Humans intervene in aquatic habitats in three ways (Falkenmark 2003):
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Flow control of rivers to fit the seasonality of water flow to the seasonal water demands. Beside dams and reservoirs also well drilling and groundwater pumping manipulates water flows.
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Land cover changes such as cutting down vegetation (deforestation) or altered use for agricultural development.
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Water extraction for consumption and irrigation.
The Millennium Declaration of the United Nations aims to halve the percentage of the population suffering from poverty, hunger and lack of safe drinking water and sanitation in 1990 by 2015. To achieve these goals humans will intervene in the ecosystem with potentially negative effects on biodiversity. Falkenmark describes this as the ‘basic dilemma’:
“Humans and ecosystems share the same water.”
Because both, humans and ecosystems are fully depending on water, Integrated Water Resourses Management (IWRM) offers an approach to balance the protection of ecosystems and the demand for water to secure human livelihoods.
Logging forests for land preparation in Upper Kunene River basin.
Source: Tump 2004
( click to enlarge )
Human Impacts on Biodiversity
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Type
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Definition
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Impact
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Overexploitation
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Overexploitation (or over harvesting) refers to harvesting a renewable source at a rate that is unsustainable
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Overexploitation can effect various natural resources such as grazing pastures (overgrazing), fish stocks (over fishing), and forests (over logging)
Overexploitation harms and can destroy habitats and the species depending on this habitat
Continuous overexploitation can lead to the destruction of the resource |
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Alien species introduction
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Alien species living outside its native distributional range, which have arrived there by human activity, either intentional or accidental
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Alien invasive species often do not have natural enemies in the invaded region. They compete with indigenous species for space and nutrients and may dispossess them
Invasive species represent the second leading cause of species extinction and loss of biodiversity in aquatic environments worldwide |
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Pollution
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Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem
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Pollution consists of agricultural, urban, and industrial wastes containing contaminants such as sewage, fertilizer, and heavy metals
Many of the pollutants entering ecosystems are very toxic to living organisms, it has proven to be very damaging to habitats and species
They can lower reproductive success, prevent proper growth and development, and even cause death. |
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Habitat fragmentation and habitat destruction
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Habitat fragmentation is caused when vegetation is cleared for agriculture, rural development, urbanization and the creation of hydroelectric reservoirs
Habitat degradation, fragmentation, and pollution are aspects of habitat destruction
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Habitats which were once continuous become divided into separate fragments
It affects biodiversity by reduction in the dimension and amount of available habitat.
In smaller patches of habitat the competition for nutrition and space between animals increases
Migration routes may become disconnected causing problems for mobile animals to move between habitats |
Adapted from US Environmental Protection Agency
www.epa.gov and various sources
