Climate Change

Writing team: Gordana Kranjac-Berisavljevic (Ghana), Balgis Osman-Elasha (Sudan), Wahida Patwa Shah (Kenya), John M.R. Stone (Canada)

Why is climate change important to achieving development and sustainability goals? The threat of climate change con­tains the potential for irreversible damage to the natural re­source base on which agriculture depends and hence poses a grave threat to development. In addition, climate changes are taking place simultaneously with increasing demands for food, feed, fiber and fuel [ESAP Chapter 4; NAE Chap­ter 3]. Addressing these issues will require a wide range of adaptation and emission reduction measures.
     The climate change issue presents decision makers with a set of formidable challenges not the least of these is the in­herent complexity of the climate system [CWANA Chapter 1; ESAP Chapter 4; LAC Chapter 3; NAE Chapter 3]. These complexities include the long time lags between greenhouse gas11 emissions and effects, the global scope of the problem but wide regional variations, the need to consider multiple greenhouse gases and aerosols, and the carbon cycle, which is important for converting emissions into atmospheric con­centrations. Another significant challenge is the rapidity of the changes in the climate that have occurred or will occur [NAE Chapter 3].

Dependency of agriculture on climate. Agricultural produc­tion depends on the provision of essential natural ecosys­tems inputs such as adequate water quantity and quality, soil nutrients, biodiversity and atmospheric carbon dioxide to deliver food, fiber, fuel and commodities for human use and consumption. The ecosystem services that provide these inputs are affected, both directly and indirectly, by climate change [CWANA Chapter 1; ESAP Chapters 2, 4; Global Chapter 1; SSA Chapter 4]. Climate change, for example, can affect the agrobiodiversity necessary for crop, tree and livestock improvement, pest control and soil nutrient cy­cling.
     Agricultural production has always been affected by

11  Greenhouse gases and clouds in the atmosphere absorb the majority of the long-wave radiation emitted by the Earth's sur­face, modifying the radiation balance and, hence, the climate of the Earth. The primary greenhouse gases are of both, natural and anthropogenic origin, including water vapour, carbon dioxide [CO2], methane [CH4] nitrous oxide [N2O] and ozone [O3], while halocarbons and other chlorine- and bromine-containing sub­stances are entirely anthropogenic.

natural climate variability and extreme climate events have caused significant damage to agriculture and livelihoods re­sulting in food insecurity and poverty among rural commu­nities [CWANA Chapter 3; ESAP Chapter 4; LAC Chapter 3; NAE Chapters 2,3; SSA Chapter 1]. Throughout human history people all over the world have learned to adapt to such climate variability and extreme events. However, ex­perience with adaptive measures differs widely among re­gions, countries and continents, as do the risks involved [NAE Chapter 3]. This Assessment provides many exam­ple of climate change's effects on food production, agro-forestry, animal production systems, fisheries and forestry [CWANA Chapter 1; ESAP Chapters 2, 4; LAC Chapter 3; NAE Chapters 1,3; SSA Chapter 4]. Poor, forest depen­dent people and small-scale fishers who lack mobility and livelihood alternatives suffer disproportionately from cli­matic variability. The El Nino-Southern Oscillation (ENSO) phenomenon, associated with massive fluctuations in the marine ecosystems of the western coast of South America, adversely affects fishing and has led to devastating socioeco-nomic tolls on the communities that depend on this activity [LAC Chapter 1] Access to training, education, credit, tech­nologies and other agricultural resources affects the ability of women in particular to cope with climate change-induced stresses.

Dependency of climate on agriculture. The relationship be­tween climate change and agriculture (crops, livestock and forestry) is not a one-way street. [Global Chapter 1; NAE Chapter 2]. Agriculture contributes to climate change in several major ways including:
•   Land conversion and plowing releases large amounts of stored carbon as CO2 from vegetation and soils. About 50% of the world's surface land area has been converted to land for grazing and crop cultivation resulting in a loss of more than half of the world's forests. Deforesta­tion and forest degradation releases carbon through the decomposition of aboveground biomass and peat fires and decay of drained peat soils.
•   Carbon dioxide (CO2) and particulate matter are emit­ted from fossil fuels used to power farm machinery, ir­rigation pumps, and for drying grain, etc., as well as fertilizer and pesticide production [NAE Chapter 2].
•   Nitrogen fertilizer applications and manure applica­tions as well as decomposition of agricultural wastes results in emissions of nitrous oxide (N2O).
•   Methane (CH4) is released through livestock digestive processes and rice production.