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Biodiversity A Global Outlook

6. What are the main threats to biodiversity?

  • 6.1 How are human activities affecting the amount of nitrogen in the environment?
  • 6.2 How serious is the threat to biodiversity posed by invasive alien species?

The third focal area of the 2010 framework concerns the five major threats to biodiversity: invasive alien species, climate change, nutrient loading and pollution, habitat change, and overexploitation. Unless we successfully reduce the impacts of these threats, they will contribute to the loss of biodiversity components, negatively affect ecosystem integrity and progress towards sustainable use. More...

6.1 How are human activities affecting the amount of nitrogen in the environment?

The growing productivity of agriculture can be attributed to a number of factors, including the availability and use of fertilizers on a commercial scale. However, nitrogen and phosphorus from those fertilizers are now causing concern. The deposition of airborne nitrogen from human activities changes the balance of ecosystems, mainly where slow growing species that thrive in nitrogen-poor environments cannot compete with faster-growing species that depend on higher nutrient levels. Temperate grasslands are particularly vulnerable in this respect. Moreover, soluble nitrogen can find its way into lakes and coastal environments, resulting in increased eutrophication, algal blooms and the creation of oxygen-depleted zones in inshore marine areas. These impacts greatly reduce the populations of fish and other aquatic species.

The rate of increase in the human production of nitrogen has accelerated sharply since 1960, and in order to continue to meet global demand for food and fibre and minimize environmental problems, significant improvements are required in the efficiency with which nitrogen fertilizer is utilized. More...

6.2 How serious is the threat to biodiversity posed by invasive alien species?

Invasive alien species can have devastating impacts on native species, causing extinctions and affecting natural and cultivated ecosystems. It has contributed to the loss of 40% of all animal extinctions for which the cause is known since the 17th century and, in one area of South Africa, it is threatening 80% of the local native species. In the recent past, the rate and risk associated with alien species introductions have increased significantly because human population growth and human activities altering the environment have escalated rapidly, combined with the higher likelihood of species being spread as a result of increased travel, trade and tourism.

A major source of marine introductions of alien species is hull fouling and the release of ballast water from ships. Of the 150 species that have recently arrived in the Great Lakes of North America, for example, 75% originated from the Baltic Sea, through well-used shipping lanes. Communicating the challenges posed by invasive alien species effectively will require a methodology for quantifying the threat to develop a coherent indicator of its impacts on biodiversity. More...

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