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Biodiversity A Global Outlook

4. At what pace is biodiversity lost?

  • 4.1 How is the extent of forests and other ecosystems changing?
  • 4.2 How is the abundance and distribution of selected species changing?
  • 4.3 What proportion of species is threatened?
  • 4.4 How is genetic diversity of cultivated and domesticated species changing?
  • 4.5 How large are protected areas?

The source document for this Digest states:

FOCAL AREA | Reducing the rate of loss of the components of biodiversity, including: (i) biomes, habitats and ecosystems; (ii) species and populations; and (iii) genetic diversity

The first of seven focal areas of the 2010 framework is reducing the rate of biodiversity loss at ecosystem, species and genetic levels, with corresponding indicators established on trends within each of these levels. Indicators under this focal area also include trends in protected area coverage and status of threatened species.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p.23

4.1 How is the extent of forests and other ecosystems changing?

The source document for this Digest states:

HEADLINE INDICATOR Trends in extent of selected biomes, ecosystems and habitats

Ecosystems are dynamic and complex assemblages of organisms that interact with each other and with the physical environment. Conversion, degradation, or the unsustainable management of a natural ecosystem has far-reaching consequences: it results in a change of the relative abundance of individual species, and frequently the loss of populations, and also in the reduction or loss of ecosystem services. Over the last 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history. Reducing the rate at which ecosystems are being degraded or lost is therefore a key contribution towards the achievement of the 2010 Biodiversity Target.

For most of the world’s main habitats and ecosystems, neither the current global extent nor rates of change in that extent are known with high certainty. This is due in part to the challenges of measuring global habitat extent, differences in definitions and classification systems and the lack of historical data. The exception is forests, many of which have direct commercial and/or scientific value, and are therefore regularly inventoried and assessed in most countries. Even here, however, there are limitations in analyses to date that make it difficult to assess, for example, changes in primary forests.

In the absence of human influence, forests and woodlands covered approximately half of the Earth’s land surface. However, thousands of years of human activity have reduced their extent to about 30% of total land area. Of this area only one-third is considered primary forest—forest of native species where ecological processes are not significantly disturbed by human activities. Deforestation, mainly conversion of forests to agricultural land and pasture, continues at an alarmingly high rate: about 13 million hectares—equivalent to the area of Greece or Nicaragua—are lost each year. At the same time, tree planting, landscape restoration and natural expansion of forests have significantly offset the loss of primary forest area. It should be borne in mind, however, that the biodiversity value of forest plantations and secondary forests is generally much lower than that of forests. Figure 2.1 presents the trends in net forest area by region. The net loss in forest area in the period 2000–2005 is estimated at 7.3 million hectares per year, equivalent to an annual loss of 0.18% of net forest area. This compares to 8.9 million hectares (0.22%) per year from the period 1990 to 2000. Over the last 15 years, primary forest has been lost or modified at a rate of approximately six million hectares a year.

Africa and South America continue to have the largest net loss of forests. Oceania and North and Central America also show a net loss of forests. The forest area in Europe continued to expand, although at a slower rate. Asia, which had a net loss in the 1990s, reported a net gain of forests in the period 2000–2005, primarily due to large-scale afforestation reported by China. There is recent evidence, however, of increases in the frequency and extent of natural disturbances (fire, insect outbreaks and disease) in boreal forests, which negatively affect forest cover in those ecosystems.

Achievement of the 2010 Biodiversity Target requires a significant reduction in the current rate of reduction of the extent of ecosystems. With regard to forests, a 20% reduction in the current rate of net loss of forest extent (7.3 million ha/yr lost between 2000 and 2005) would require limiting forest loss to 5.84 million ha/yr by 2010, while a 50% reduction would mean no more than 3.65 million ha/yr of forest loss. At the same time, efforts would need to focus on conserving natural forest area, rather than replacing natural forests with plantations of low biodiversity value.

On the basis of various studies from the period of 1980 to 2000, the Millennium Ecosystem Assessment prepared a map showing the areas undergoing high rates of change in forest cover (Figure 2.2)

General patterns of change in the extent of ecosystems across other biomes besides forests show similar negative trends. The Millennium Ecosystem Assessment reported that almost 70% of Mediterranean forests, woodlands and scrub, 50% of tropical and sub-tropical grasslands, savannas and shrublands and 30% of desert ecosystems had been lost by 1990. Coastal and marine ecosystems have been heavily impacted by human activities, with degradation leading to a reduced coverage of kelp forests, seagrasses and corals. In the Caribbean, average hard coral cover declined from about 50% to 10% in the last three decades, equivalent to a loss of almost 7% of remaining area covered by live coral each year since the 1970s (Figure 2.3). Some 35% of mangroves have been lost in the last two decades in countries for which adequate data are available. This is equivalent to an annual loss of 2% of the remaining area. There has been a widespread retreat of mountain glaciers in non-polar regions during the 20thcentury, and decreases of about 10% in the extent of snow cover since the late 1960s. In the Arctic the average annual sea ice extent has declined by about 8% in the past 30 years, with a loss of 15 to 20% in summer sea ice extent over the same period.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p.23-25

4.2 How is the abundance and distribution of selected species changing?

The source document for this Digest states:

HEADLINE INDICATOR Trends in abundance and distribution of selected species

Species population trend indices are valuable tools for monitoring and communicating biodiversity change at global, regional and (sub-) national scales, or within biogeographic units. They can also be applied to taxonomic groups (e.g., birds), habitat-dependent species (e.g., waterfowl) or species with particular ecological characteristics (e.g., migratory species).

Trends in abundance and distribution of selected species is an indicator of ecosystem quality and complements the foregoing measures of ecosystem extent. Other indicators such as connectivity/fragmentation of ecosystems are also relevant in providing information about the quality of ecosystems.

A number of assessments have revealed that, across a range of taxonomic groups, the population size and/or geographic range of the majority of species assessed is declining. Studies of amphibians globally, African mammals, birds in agricultural lands, British butterflies, Caribbean and Indo-pacific corals, and commonly harvested fish species show declines in the majority of these species. Exceptions include species that have been protected through specific measures, that have had their specific threats reduced, and those that tend to thrive in modified landscapes.

Based on published data from around the world, the Living Planet Index aggregates trends of some 3,000 wild populations of species. It shows a consistent decline in average species abundance of about 40% between 1970 and 2000; inland water species declined by 50%, while marine and terrestrial species both declined by around 30% (Figure 2.4).

Because of limitations in data availability, species rich tropical areas (particularly forests) are underrepresented in the Living Planet Index, and the data are limited to vertebrates. Efforts are underway to expand the data set and to include information on the distribution of selected populations of plant species. According to this analysis, wild populations of species declined by an aggregated average of about 1.7% per year between 1970 and 2000, with a particularly significant decline in the early 1990s.

Similar trends have been observed for abundant and widespread farmland and forest-dependent bird species throughout Europe (Figure 2.5). European farmland birds declined by about 1.4% per year between 1970 and 2000 with a particularly severe decline of over 3% per year in the late 1970s and 1980s and a stabilization of populations in the 1990s. European forest birds show some signs of recovery since 2000.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p.25-26

4.3 What proportion of species is threatened?

The source document for this Digest states:

HEADLINE INDICATOR Change in status of threatened species

Threatened species occur across all taxonomic groups and in all parts of the world. Over the past few hundred years, it is estimated that humans have increased species extinction rates by as much as 1,000 times the background rates typical over Earth’s history. Between 12% and 52% of species within well-studied higher taxa are threatened with extinction, according to the IUCN Red List of Threatened Species.

On the basis of Red List data, a Red List Index can be calculated for different taxonomic groups or geographic regions to show trends in the proportion of species expected to remain extant in the near future without additional conservation interventions. The index is based on the number of species present in each Red List category, and on the number that change categories over time (i.e., between assessments), as a result of genuine improvement or deterioration in status. This index shows a continuing deterioration in the status of bird species, which have been completely assessed for the IUCN Red List four times over the last two decades, across all biomes (Figure 2.6). Despite limitations in our knowledge about the total number of species and their status, preliminary findings for other major groups, such as amphibians and mammals, indicate that the situation is likely worse than for birds.

The Red List Index is highly representative, being based on assessments of a high proportion of species in a taxonomic group across the world, but it shows a coarse level of resolution because of the width of the Red List categories. Some of the Red List criteria are based on absolute population size or range size, while others are based on rates of decline in these values or combinations of absolute size and rates of decline. Because the Red List Index is based on a proportional change in a measure and its values relate to the rate at which species are slipping towards extinction at particular points in time, a downward trend, even if becoming less steep, shows that the slide of the species towards extinction is accelerating, rather than slowing down. The 2010 Biodiversity Target would therefore only be met when a positive trend is achieved.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p. 26-27

4.4 How is genetic diversity of cultivated and domesticated species changing?

The source document for this Digest states:

HEADLINE INDICATOR Trends in genetic diversity of domesticated animals, cultivated plants, and fish species of major socio-economic importance.

From a human perspective, genetic diversity is of particular importance in cultivated and domesticated species. Only a relatively small number of species are used in this way: a few dozen domesticated animals, a few hundred crop plants (if ornamental plants are excluded), and a few dozen major plantation timber species.

An analysis of trends in the varieties of species that underpin human livelihood, while sketchy, provides an alarming picture. Genetic variation is important for maintaining fitness and adaptability of species, and of direct importance for people through the maintenance of goods and services provided by cultivated and domesticated species: high yields, disease resistance and resilience to changing environmental conditions. Human well-being, particularly food security, depends at present on a small group of crops and domestic animals; failure of one individual crop can have far-reaching consequences. Loss of genetic diversity through the disappearance of locally adapted varieties and land-races of crops and livestock breeds is widely reported but difficult to quantify. It has been estimated that one third of the 6,500 recognized domesticated animal breeds are currently threatened with extinction.

Beyond cultivated systems, over-exploitation of wild harvested species, including several marine fish species, has led to decline of population size and distribution and as a consequence has contributed to the loss of genetic diversity. Selective trophy hunting of game and selective removal of valuable timber trees can change the genetic profile of the remaining populations. More generally, loss of genetic diversity is associated with the decline in population abundance and distribution that result from habitat destruction and fragmentation.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p.27

4.5 How large are protected areas?

The source document for this Digest states:

HEADLINE INDICATOR Coverage of protected areas

A key tool to counter the continuing loss of ecosystems and species is the establishment of protected areas. Protected areas currently cover about 12% of the Earth’s land surface, constituting one of the largest planned changes of land use. Of more than 105,000 protected areas listed in the World Database on Protected Areas about 60% have a known date of establishment. Figure 2.7 presents the trends in surface under protection by IUCN Protected Area Management Categories. About 12% of the area under protection has not been assigned a Protected Area Management Category. Among all categories, National Parks (category II) and Managed Resource Protected Area (category VI) show a particularly high increase in recent decades.

Moreover, there are substantial differences in coverage between different biomes, ecosystems and habitats. Only 5% of the world’s temperate needle-leaf forests and woodlands, 4.4% of temperate grasslands and 2.2% of lake systems are protected. Moreover, marine coverage lags far behind terrestrial coverage, with approximately 0.6% of the ocean’s surface area and about 1.4% of the coastal shelf areas protected.

A more detailed analysis of the 825 terrestrial ecoregions and 64 large marine ecosystems shows that for a large percentage of these ecosystems, which are characterized by distinct populations of species, the target of 10% protected area coverage is yet to be achieved (Figure 2.8).

In Figure 2.9 terrestrial ecoregions are ordered by percentage under protection. While over 5% of ecoregions are completely protected, in three out of five ecoregions less than 10% of the surface is protected. In 140 ecoregions, equivalent to 17% of all ecoregions, less than 1% of the surface is designated as a protected area.

However, the growth in number and area of protected areas is a fairly crude indicator in itself, and needs to be complemented by further information on the level of protection afforded to biodiversity and the effectiveness of management. Various methodologies are being used to measure effectiveness of protected area management and are contributing enormously to an understanding of the role of protected areas in reducing the rate of loss of biodiversity but systematic data are not yet available.

Source & ©: CBD  Global Biodiversity Outlook 2 (2006),
Chapter 2: The 2010 Biodiversity Target: Establishing current trends, p.27-29

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