Climate change impacts
Observed evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increase. Current knowledge about future impacts provides more specific information across a wide range of natural systems and sectors. Although the word "impact" has a negative connotation, it is likely that impacts will not only be negative, depending on scale (e.g. plant, field, ecosystem), country, climate, etc.
Poor countries and communities are especially vulnerable
Several potentially positive effects have been identified, for instance reduced plant water use and "CO2 fertilisation". Cold climates would benefit from higher temperatures, increased frost free periods. New agricultural land may become available at high latitudes and high elevations. However, poor countries and communities are especially vulnerable to climate change due to their concentration in high-risk areas, their limited adaptive capacity and high dependence on climate-sensitive resources such as local water and food supplies.
Climate change impacts vary regionally
Impacts of climate change will vary regionally but, aggregated and discounted to the present, they are very likely to impose net annual costs which will increase over time as global temperature increase. In general, however, complex studies taking into account physiological effects, shifting climatic zones, effects of global warming on soils and socio-economic variables such as adaptive capacity, generally conclude to neutral or positive impacts in some temperate countries, and mostly negative impacts in the developing world. Overall impacts of climate change (including extreme weather events) on agriculture and a regional breakdown of impacts are summarized in Table 1 and 2, respectively.
FAO maintains global databases for indicators of climate change impacts under GTOS and other programmes. FAO also conducts climate change impact assessments on agriculture in a number of countries.
| Phenomenon and direction of trend in extreme weather and climate events | Likelihood of future trends based on projections for 21st century | Possible impacts on agriculture, forestry and ecosystems |
|---|---|---|
| Over most land areas, warmer and fewer cold days and nights, warmer and more frequent hot days and nights | Virtually certain | Increased yields in colder environments; decreased yields in warmer environments; increased insect outbreaks |
| Warm spells/heat waves. Frequency increased over most land areas | Very likely | Reduced yields in warmer regions due to heat stress; increased danger of wildfire |
| Heavy precipitation events. Frequency increases over most areas | Very likely | Damage to crops; soil erosion, inability to cultivate land due to water logging of soils |
| Area affected by drought increases | Likely | Land degradation; lower yields/crop damage and failure; increased livestock deaths; increased risk of wildfire |
| Intense tropical cyclone activity increases | Likely | Damage to crops; windthrow (uprooting) of trees; damage to coral reefs |
| Increased incidence of extreme high sea level (excludes tsunamis) | Likely | Salinisation of irrigation water, estuaries and freshwater systems |
| Region | Possible impacts on agriculture, forestry and ecosystems |
|---|---|
| Africa | By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%. Agricultural production, including access to food, in many African countries is projected to be severely compromised. This would further adversely affect food security and exacerbate malnutrition. |
| Asia | By the 2050s, freshwater availability in Central, South, East and South-East Asia, particularly in large river basins, is projected to decrease. |
| Latin America | By mid century, increases in temperature and associated decreases in soil water are projected to lead to gradual replacement of tropical forest by savanna in eastern Amazonia. Semi-arid vegetation will tend to be replaced by arid-land vegetation. Productivity of some important crops is projected to decrease and livestock productivity to decline, with adverse consequences for food security. In temperate zones soybean yields are projected to increase. Overall, the number of people at risk of hunger is projected to increase. |
| Small Islands | Sea-level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening vital infrastructure, settlements and facilities that support the livelihood of island communities. |
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last updated: Wednesday, March 18, 2009