Biodiversity A Global Outlook

5. Are ecosystems healthy enough to provide resources and essential services?

• 5.1 How is fishing affecting marine species?
• 5.2 How are human activities fragmenting forests and inland waters?
• 5.3 How is freshwater quality changing?

The second focal area of the 2010 framework is maintaining the integrity of ecosystems and their ability to support human livelihoods through the provision of the goods and services they guarantee. More...

5.1 How is fishing affecting marine species?

See also our Digest on Fisheries

Trends in mean trophic levels of fisheries landings (1950-2000)

Oceans cover over 70% of the globe. The primary source of food from the oceans is capture fisheries, and the preferred species for capture are large predatory fish such as tuna and cod. Intense fishing has led to the decline of these species. In the North Atlantic, for instance, large fish have declined by two-thirds in the last 50 years. As a result, the relative number of small fish and invertebrates lower on the food chain increased, and the average position in the food chain (mean trophic level) of the fish captured has declined as a reflection of this. This measure has been declining globally since the 1970s. The preferred fish for human consumption are becoming increasingly rare, forcing a shift in fisheries and human consumption patterns to smaller fish and invertebrates, and eventually reducing the overall supply of wild fish for human consumption. Despite an increase in fishing effort, marine fisheries decreased throughout the 1990s.

The Marine Trophic Index, which measures the change in mean trophic level, can be calculated from existing data on fish catch and is therefore a widely applicable indicator of ecosystem health and sustainable use of its living resources. If action were taken to better manage fisheries, declines in the Marine Trophic Index could be halted, as seen in Alaska, where the Index has stabilized with the sound management of most Alaskan fish stocks. More...

5.2 How are human activities fragmenting forests and inland waters?

Estimates of forest fragmentation due to anthropogenic causes

In many terrestrial and inland water ecosystems, human activities lead to the fragmentation of habitats. The resulting smaller patches of habitat support smaller populations of species, which then become more vulnerable to local extinction. Forests and river systems are two systems where fragmentation can be relatively easily assessed, and both show high levels of fragmentation.

In river systems, for instance, reservoirs have significant effects on the flow of water and its quality, as well as on its biodiversity, particularly that of migratory species. The impacts of dams on ecosystems include the destruction of terrestrial ecosystems through inundation, greenhouse gas emissions, and extensive modification of aquatic communities. A global overview of dam-based impacts assessed fragmentation and flow regulation in 60% of the world’s river runoff. Over half of the assessed large river systems were shown to be affected by dams, and more than one-third are strongly affected by river fragmentation and flow regulation. Only 12% of the area is unaffected. More...

5.3 How is freshwater quality changing?

Pollution, increased sedimentation, climate change, the extraction of fresh water for agricultural, industrial and human consumption, and the physical alteration of the ecosystem, for example through the diversion and canalization of watercourses, have all affected the quality of inland waters. For instance, nitrogen pollution of inland waterways, coming mainly from the use of fertilizers, has more than doubled since 1960 and has increased tenfold in many industrial parts of the world.

While water quality in rivers in Europe, North America, and Latin America and the Caribbean has improved since the 1980s, it has deteriorated over the same period in Africa and in the Asia and Pacific region.

Water quality monitoring indicates both major direct threats to the sustainability of inland waters and the effects of unsustainable activities outside that ecosystem. The health and integrity of inland waters is an excellent indicator of the health of terrestrial ecosystems. Improving water quality in all regions appears to be a tangible, though challenging, contribution to the achievement of the 2010 Biodiversity Target. More...