Global biodiversity outlook 31
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The conifer-dominated boreal forests of high Northern latitudes have remained broadly stable in extent in recent years. However, there are signs in some regions that they have become degraded. In addition, both temperate and boreal forests have become more vulnerable to outbreaks of pests and diseases, due in part to an increase in winter temperatures. For example an unprecedented outbreak of the mountain pine beetle has devastated more than 110,000 square kilometres of forest in Canada and the Western United States since the late 1990s60. Savannas and grasslands, while less well documented, have also suffered severe declines The extent of other terrestrial habitats is less well documented. It is estimated that more than 95 per cent of North American grasslands have been lost61. Cropland and pasture have replaced nearly half of the cerrado, the woodland-savanna biome of Central Brazil which has an exceptionally rich variety of endemic plant species. Between 2002 and 2008, the cerrado was estimated to have lost more than 14,000 square kilometres per year, or 0.7% of its original extent annually, well above the current rate of loss in the Amazon62. The Miombo woodlands of Southern Africa, another savanna region with significant plant diversity, are also experiencing continued deforestation. Stretching from Angola to Tanzania and covering an area of 2.4 million square kilometres (the size of Algeria), the Miombo provide firewood, building material and extensive supplies of wild food and medicinal plants to local communities across the region. The woodlands are threatened by clearing land for agriculture, extraction of wood to make charcoal, and uncontrolled bush fires63,64,65. Abandonment of traditional agricultural practices may cause loss of cultural landscapes and associated biodiversity. Traditional techniques of managing land for agriculture, some dating back thousands of years, have served an important function in keeping human settlements in harmony with the natural resources on which people depend66. [See Box 6]. In many parts of the world, these systems are being lost, due partly to the intensification of production, and partly to abandonment linked to migration from rural to urban areas. In some cases, this trend may create opportunities for biodiversity through the re-establishment of natural ecosystems on abandoned farmland. However, the changes may also involve important losses of distinctive biodiversity, among both domesticated and wild species, and of ecosystem services provided by managed landscapes67.
Terrestrial habitats have become highly fragmented, threatening the viability of species and their ability to adapt to climate change. Ecosystems across the planet, including some with exceptionally high levels of biodiversity, have become severely fragmented, threatening the long-term viability of many species and ecosystem services73. Global data regarding this process are hard to obtain, but some well-studied ecosystems provide illustrations of the scale of fragmentation and its impacts. For example, the remaining South American Atlantic Forest, estimated to contain up to eight per cent of all terrestrial species, is largely composed of fragments less than one square kilometre in size74. More than 50 per cent lies within 100 metres of the forest edge75. When ecosystems become fragmented they may be too small for some animals to establish a breeding territory, or force plants and animals to breed with close relatives. The in-breeding of species can increase vulnerability to disease by reducing the genetic diversity of populations. A study in the central Amazon region of Brazil found that forest fragments of less than one square kilometre lost half of their bird species in less than fifteen years. In addition, isolated fragments of habitat make species vulnerable to climate change, as their ability to migrate to areas with more favourable conditions is limited76. One-quarter of the world’s land is becoming degraded. The condition of many terrestrial habitats is deteriorating. The Global Analysis of Land Degradation and Improvement estimated that nearly one quarter (24%) of the world’s land area was undergoing degradation, as measured by a decline in primary productivity, over the period 1980-2003. Degrading areas included around 30% of all forests, 20% of cultivated areas and 10% of grasslands. Geographically they were found mainly in Africa south of the Equator, South-East Asia and southern China, north-central Australia, the Pampas grasslands in South America, and parts of the Siberian and North American boreal forests. Around 16 per cent of land was found to be improving in productivity, the largest proportion (43%) being in rangelands. The areas where a degrading trend was observed barely overlapped with the 15% of land identified as degraded in 1991, indicating that new areas are being affected and that some regions of historical degradation remain at stubbornly low levels of productivity. About 1.5 billion people directly depend on ecosystem services provided by areas that are undergoing degradation. The decline in fixation of carbon from the atmosphere associated with this degradation is estimated at nearly a billion tonnes from 1980 to 2003, (almost the equivalent of annual carbon dioxide emissions from the European Union) and emissions from the loss of soil carbon are likely to have been many times greater77. Despite more than 12 per cent of land now being covered by protected areas, nearly half (44%) of terrestrial eco-regions fall below 10 per cent protection, and many of the most critical sites for biodiversity lie outside protected areas. Of those protected areas where effectiveness of management has been assessed, 13% were judged to be clearly inadequate, while more than one fifth demonstrated sound management, and the remainder were classed as “basic”. An increasing proportion of global land surface has been designated as protected areas [See Box 7 and Figure 8]. In total, some 12.2% enjoys legal protection, made up of more than 120,000 protected areas78. However, the target of protecting at least 10% of each the world’s ecological regions – aimed at conserving a representative sample of biodiversity – is very far from being met. Of the 825 terrestrial ecoregions, areas containing a large proportion of shared species and distinct habitat types, only 56% have 10% or more of their area protected79,80. [See Figure 10]
The existing protected area network also excludes many locations of special importance to biodiversity. For example, complete legal protection is given to only 26% of Important Bird Areas (IBAs), sites with significant populations of species that are threatened, have restricted geographical ranges, are confined to a single biome, or congregate in large numbers to feed or breed85. Of nearly 11,000 IBAs in 218 countries, on average some 39% of their area is included in protected areas. Similarly, only 35% of sites holding the entire population of one or more highly threatened species are fully covered by protected areas [See Box 8 and Figure 9] 86. However, the proportion of both of these categories of sites under legal protection has increased significantly in recent years.
Clearly, the benefit to biodiversity from protected areas depends critically on how well they are managed. A recent global assessment of management effectiveness has found that of 3,080 protected areas surveyed, only 22% were judged “sound”, 13% “clearly inadequate”, and 65% demonstrated “basic” management. Common weaknesses identified in the assessment were lack of staff and resources, inadequate community engagement and programmes for research, monitoring and evaluation. Aspects relating to basic establishment of the reserves and maintaining the values of the protected area were found to be quite strong88,89. Indigenous and local communities play a significant role in conserving very substantial areas of high biodiversity and cultural value. In addition to officially-designated protected areas, there are many thousand Community Conserved Areas (CCAs) across the world, including sacred forests, wetlands, and landscapes, village lakes, catchment forests, river and coastal stretches and marine areas [See Box 9]. These are natural and/or modified ecosystems of significant value in terms of their biodiversity, cultural significance and ecological services. They are voluntarily conserved by indigenous and local communities, through customary laws or other effective means, and are not usually included in official protected area statistics90. Globally, four to eight million square kilometres (the larger estimate is an area bigger than Australia) are owned or administered by communities91. In 18 developing countries with the largest forest cover, over 22% of forests are owned by or reserved for communities92. In some of these countries (for example Mexico and Papua New Guinea) the community forests cover 80% of the total93,94. By no means all areas under community control effectively conserved, but a substantial portion are. In fact, some studies show that levels of protection are actually higher under community or indigenous management than under government management alone95.
Inland waters ecosystems Inland water ecosystems have been dramatically altered in recent decades. Wetlands throughout the world have been and continue to be lost at a rapid rate. Rivers and their floodplains, lakes and wetlands have undergone more dramatic changes than any other type of ecosystem, due to a combination of human activities including drainage for agriculture, abstraction of water for irrigation, industrial and household use, the input of nutrients and other pollutants, introduction of alien species and the damming of rivers107. Verifiable global data for loss of inland water habitats as a whole are not available, but it is known that shallow-water wetlands such as marshes, swamps and shallow lakes have declined significantly in many parts of the world. Documented examples of loss include:
Water quality shows variable trends, with improvements in some regions and river basins being offset by serious pollution in many densely-populated areas. Water quality in freshwater ecosystems, an important biodiversity indicator, shows variable trends, and global data are very incomplete113. Relevant information about pollution loads and changes in water quality is lacking precisely where water use is most intense – in densely populated developing countries. As a result, the serious impacts of polluting activities on the health of people and ecosystems remain largely unreported. In some areas, depletion and pollution of economically important water resources have gone beyond the point of no return, and coping with a future without reliable water resources systems is now a real prospect in parts of the world. UNESCO’s Third World Water Development Report predicts that nearly half of humanity will be living in areas of high water stress by 2030114. Pollution control through sewage treatment and regulation of industrial effluent has had significant success in improving water quality in many inland water ecosystems [See Figure 11], although such progress has so far been very limited in developing countries. Pollution originating from diffuse or non-point sources (particularly from agriculture) remains a significant and growing problem in many parts of the world115. Of 292 large river systems, two-thirds have become moderately or highly fragmented by dams and reservoirs. Rivers are becoming increasingly fragmented, often with severe disruption to their flows. The most fragmented rivers are in industrialized regions like much of the United States and Europe, and in heavily-populated countries such as China and India. Rivers in arid regions also tend to be highly fragmented, as scarce water supplies have often been managed through the use of dams and reservoirs. Rivers flow most freely in the less-populated areas of Alaska, Canada and Russia, and in small coastal basins in Africa and Asia116. This fragmentation is important because so much of the variety of freshwater life is determined by the connections formed between different parts of a river basin, as water, sediments and nutrients flow in dynamic rhythms of flood and interaction with tidal zones on the coast. More than 40% of the global river discharge is now intercepted by large dams and one-third of sediment destined for the coastal zones no longer arrives117. These large-scale disruptions have had a major impact on fish migration, freshwater biodiversity more generally and the services it provides. They also have a significant influence on biodiversity in terrestrial, coastal and marine ecosystems. Inland water ecosystems are often poorly served by the terrestrial protected areas network, which rarely takes account of upstream and downstream impacts. Governments are reporting increased concern about the ecological condition of wetland sites of international importance (Ramsar sites). Assessing the proportion of inland water biodiversity covered effectively by the existing network of protected areas is difficult. The Millennium Ecosystem Assessment estimated that 12% of the area of the world’s inland waters was included within protected areas118. This does not, however, give an accurate indication of the proportion of the world’s river basins that enjoy protection, since the state of freshwater biodiversity at a particular location will often depend on activities far upstream or downstream – such as pollution, abstraction of water, the building of dams and deforestation. Governments of 159 countries have ratified the Ramsar Convention on Wetlands, currently committed to conserving 1,880 wetlands of international importance, covering over 1.8 million square kilometres, and to the sustainable use of wetland resources generally. The condition of these wetland protected areas continues to deteriorate, with the majority of governments reporting an increased need to address adverse ecological changes in 2005-8, compared with the previous three-year period. The countries reporting the greatest concern about the condition of wetlands were in the Americas and Africa119. In many countries, steps are being taken to restore wetlands, often involving reversals in land-use policies by re-wetting areas that were drained in the relatively recent past. A single freshwater ecosystem can often provide multiple benefits such as purification of water, protection from natural disasters, food and materials for local livelihoods and income from tourism. There is a growing recognition that restoring or maintaining the natural functions of freshwater systems can be a cost-effective alternative to building physical infrastructure for flood defenses or costly water treatment facilities.
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