Changes in the air temperature and rainfall, as well as more frequent floods and droughts will have long-term effects on the viability and productivity of world agro-ecosystems, said Alexander Müller, FAO Assistant Director General. In anticipation of these challenges, agricultural systems need to be adapted to the changed conditions and specific stresses. One way of doing this would be introducing crop varieties that can tolerate heat and water stress, Müller told attendees at a workshop on Adaptation Planning and Strategies, held in Rome today. "While continuing to deal with the causes of climate change - by reducing emissions and increasing greenhouse gas sinks - it is crucial to also take immediate action to cope with its effects. Ways must be found to build up peoples' resilience as well as that of food production systems," he said. According to FAO, agriculture is both the culprit and the victim when it comes to climate change. For example, the livestock sector is thought to account for 18 percent of global greenhouse gas emissions, while deforestation is responsible for 18 percent of carbon dioxide emissions. Rice production is another major source of greenhouse gas emissions. At the same time, however, adverse and extreme weather conditions can jeopardize rice crop production, which feeds more than half of the world's population, said FAO. "Of major benefit would be introducing different and improved rice varieties with greater salinity tolerance. These were successfully used by FAO to expedite the recovery of production in areas damaged by the 2004 Asian tsunami," it said. More hardy varieties, yielding over four tons per hectare, have been developed and tested successfully in Bangladesh, a country repeatedly affected by flooding. Other steps that could be taken include improved livestock management and crop practices, as well as land use practices such as conservation agriculture. According to FAO, climate change is a global phenomenon with local or regional features that needs to be understood and anticipated. "FAO is already actively assisting its members, particularly developing countries, to enhance their capacity to confront the negative impacts of climate change on agriculture, forests and fisheries," said Müller. According to a study published earlier this year in the journal Environmental Research Letters, warming temperatures have caused annual losses of roughly $5bn for major food crops. Researchers at the Carnegie Institution and Lawrence Livermore National Laboratory reported that from 1981 to 2002, warming reduced the combined production of wheat, corn, and barley - cereal grains that form the foundation of much of the world's diet - by 40m metric tons per year. The study claimed to be the first to estimate how much global food production has already been affected by climate change. Researchers compared yield figures from the Food and Agriculture Organization with average temperatures and precipitation in the major growing regions. They found that, on average, global yields for several of the crops responded negatively to warmer temperatures, with yields dropping by about three to five percent for every one degree F increase. Average global temperatures increased by about 0.7 degrees F during the study period, with even larger changes in several regions.