Synthesis Report - Question 8

Land Degradation and Desertification and Climate Change

8.18

Projected levels of climate change would exacerbate the continuation of land degradation and desertification that has occurred over the past few centuries in many areas. Land-use conversion and the intensive use of land, particularly in the world's arid and semi-arid regions, has resulted in decreased soil fertility and increased land degradation and desertification. The changes have been large enough to be apparent from satellite images. Land degradation already affects more than 900 million people in 100 countries, and one quarter of the world soil resources, most of them in the developing countries. The annual recorded losses of millions of hectares significantly undermine economies and create some irreversible situations. The TAR projections using the SRES scenarios indicate increased droughts, higher intensity of rainfall, more irregular rainfall patterns, and more frequent tropical summer drought in the mid-latitude continental interiors. The systems that likely would be impacted include those with scarce water resources, rangelands, and land subsidence (see Table 8-2).

WGI TAR Sections 2.7.3.3, 9.3, & 10.3, WGII TAR Section 5.5, & WGII TAR Table SPM-1

Table 8-1: Examples for observed and projected regional implications of climate change on natural ecosystems, biodiversity, and food supply.
Region	Impacts	Reference Section in WGII TAR
Africa	Irreversible losses of biodiversity could be accelerated with climate change. Significant extinctions of plant and animal species are projected and would impact rural livelihoods, tourism, and genetic resources (medium confidence).	TS 5.1.3 & Section 10.2.3.2
Asia	Decreases in agricultural productivity and aquaculture due to thermal and water stress, sea-level rise, floods and droughts, and tropical cyclones would diminish food security in many countries of arid, tropical, and temperate Asia; agriculture would expand and increase in productivity in northern areas (medium confidence). Climate change would exacerbate threat to biodiversity due to land-use and land-cover change and population pressure (medium confidence). Sea-level rise would put ecological security at risk including mangroves and coral reefs (high confidence).	TS 5.2.1-2 & Sections 11.2.1 2
Australia and New Zealand	A warming of 1ºC would threaten the survival of species currently near the upper limit of their temperature range, notably in marginal alpine regions. Some species with restricted climatic niches and that are unable to migrate due to fragmentation of the landscape soil differences or topography could become endangered or extinct (high confidence). Australian ecosystems that are particularly vulnerable to climate change include coral reefs, arid and semi-arid habitats in southwest and inland Australia, and Australian alpine systems. Freshwater wetlands in coastal zones in both Australia and New Zealand are vulnerable, and some New Zealand ecosystems are vulnerable to accelerated invasion by weeds.	TS 5.3.2 & Sections 12.4.2, 12.4.4-5, & 12.4.7
Europe	Natural ecosystems will change due to increasing temperature and atmospheric concentration of CO₂. Diversity in nature reserves is under threat of rapid change. Loss of important habitats (wetlands, tundra, and isolated habitats) would threaten some species, including rare/endemic species and migratory birds. There will be some broadly positive effects on agriculture in northern Europe (medium confidence); productivity will decrease in southern and eastern Europe (medium confidence).	TS 5.4.2-3 & Sections 13.2.1.4, 13.2.2.1, 13.2.2.3-5, & 13.2.3.1
Latin America	It is well-established that Latin America accounts for one of the Earth's largest concentrations of biodiversity and the impacts of climate change can be expected to increase the risk of biodiversity loss (high confidence). Yields of important crops are projected to decrease in many locations even when the effects of CO₂ are taken into account; subsistence farming in some regions could be threatened (high confidence).	TS 5.5.2 & 5.5.4, & Sections 14.2.1-2
North America	There is strong evidence that climate change can lead to the loss of specific ecosystem types (e.g., high alpine areas and specific coastal (salt marshes and inland prairie "potholes") wetlands) (high confidence). Some crops would benefit from modest warming accompanied by increasing CO₂, but effect would vary among crops and regions (high confidence), including declines due to drought in some areas of Canada's Prairies and the U.S. Great Plains, potential increased food production in areas of Canada north of current production areas, and increased warm temperate mixed forest production (medium confidence). However, benefits for crops would decline at an increasing rate and possibly become a net loss with further warming (medium confidence). Unique natural ecosystems such as prairie wetlands, alpine tundra, and coldwater ecosystems will be at risk and effective adaptation is unlikely (medium confidence).	TS 5.6.4-5 & Sections 15.2.2-3
Arctic	The Arctic is extremely vulnerable to climate change, and major physical, ecological, and economic impacts are expected to appear rapidly.	TS 5.7 & Sections 16.2.7-8
Antarctic	In the Antarctic projected climate change will generate impacts that will be realized slowly (high confidence). Warmer temperatures and reduced ice extent are likely to produce long-term changes in the physical oceanography and ecology of the Southern Ocean, with intensified biological activity and increased growth rate of fish.	TS 5.7 & Sections 16.2.3 & 16.2.4.2
Small Islands	Projected future climate change and sea-level rise will affect shifts in species composition and competition. It is estimated that one out of every three (30%) known threatened plants are island endemics, while 23% of bird species are threatened. Coral reefs, mangroves, and seagrass beds that often rely on stable environmental conditions will be adversely affected by rising air and sea temperatures and sea-level rise (medium confidence). Declines in coastal ecosystems would negatively impact reef fish and threaten reef fisheries (medium confidence).	TS 5.8 & Sections 17.2.4-5 & 17.2.8.2

Figure 8-2: This figure shows linkages between climate change and other environmental factors in food supply and demand. Increasing food demand by a growing world population calls for larger food production. This, in turn, brings a series of implications in the use of land, such as converting wildlands to croplands (extensification), and using chemical fertilizers and/or using irrigation to increase yield (intensification) or enabling cultivation in otherwise non-usable land. Expanding the land under cultivation results in loss of biodiversity, as ecosystems are converted to fields growing only a few species (usually exotics). Change of forests to agriculture brings a net loss of carbon to the atmosphere, as forests are replaced by grassland or cropland. This clearing also increases flooding probability, as the agricultural systems retain less precipitation than forests. Intensification of crop production can involve a variety of chemical treatments, most of them being nitrogen fertilizers bringing the side effect of release of nitrogen gas compounds (some of which are strong greenhouse gases) to the atmosphere and nitrogen runoff into watersheds, with many environmental and health implications. The expansion of irrigation affects the supply of freshwater for other uses, leading to shortages and conflicts over water-use rights. Meeting the needs for increased agricultural production has the potential to increase global rates of biodiversity loss, climate change, and desertification. There are interrelations, particularly to water, that underly all these issues, but for simplicity are not shown in the figure.

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