World populated countries and food security: At present China is the most populated country followed by India. Among the top ten populated countries in the world, six belongs to Asia i.e. China (rank 1), India (rank 2), Indonesia (rank 4), Pakistan (rank 6), Bangladesh (rank 8) and Japan is in rank 10 position. In the populated countries basic agricultural challenges are identified as food security, productivity, climate change & vulnerability and primary source of livelihood. It was observed that Asian populated countries Global Food Security Index (GFSI) is comparatively lower than that of USA (GSFI 89.5, rank 1) and European countries. The other top populated Asian countries’ are Indonesia GFSI, 46.8, 64 position, Pakistan GFSI 38.5, 75 position and Bangladesh GFSI 34.6, 81 position. Among the Asian countries first and second position are Japan (GFSI 80.7, 16 positions) and South Korea (GFSI 77.8, 21 positions). In Asian countries only seven percent of the world’s organic agricultural land is used. In the largest domestic markets for organic foods, only one Asian country Japan occupied 8th position. The largest number of organic producers lists only India is held the position number one in the top ten countries. 89% of Asian countries organic agricultural land is below 1% (organic.net. 2012). Considering the above facts, the organic production of Asia is not successful like USA and European states. Agriculture in Asia is characterized by small holders of farmland having average size of less than 2 hectares (80% of total farms). The agricultural production of these small farms is presently meeting the food need of one-third of total world population. Asian smallholders are facing several challenges arising from a range of economic, demographic, structural, technological and institutional factors including industrialization and urbanization. Shrinking size of farms, rural urban migration, environmental degradation, evolution and adoption of genetically modified crops, climate change and its impact may emerge as a future threat for Asian countries. Bangladesh food security related to population: Food security exists when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life (World Food Summit – 1996). Food security is given the topmost priority in Bangladesh. Side by side with domestic food production, greater importance is given to ensure access to adequate and safe food for all people to maintain an active and healthy life. Agriculture sector contributes about 21% of total GDP in Bangladesh, out of which crop sector shares 73%, fisheries 10%, livestock 10% and forestry 7%. Bangladesh has made a steady progress in the expansion of food production. Because of the increasing population pressure there has been an extensive use of land to meet the growing demand for food. In Bangladesh area of cultivable lands were 8.85, 8.18, 7.746, 8.44 and 9.098 m ha in 1990, 1995, 2000, 2006 and 2010 respectively. Food production during 1990, 2006 and 2010 were 14.55, 24.569 and 26.59 mMT against the requirements of 16.28, 23.029 and 24.52 mMT respectively (1) As per Global Food Security Index, Bangladesh position is lowest in the South Asian countries. 26% people are facing malnutrition and per day 290 cal is taken (where in rich country 1200 cal/per person/ per day. Decreasing arable land in Bangladesh, together with increasing population and changing climatic conditions, make this challenge more acute. Most of the agriculture production is carried out on small pieces of lands. Bangladesh's population is increasing at a rate of two million every year. Beside that, in order to feed the ever increasing population, the government of Bangladesh emphasized cereal crops production with the introduction of high-yielding varieties of rice and wheat since independence. In the last two decades, frequent floods, droughts and cyclones have caused extensive economic damage and have impaired livelihoods in Bangladesh. Adapting to and mitigating the effects of climate change is a key to sustainable development and food security issue in Bangladesh. Overall, agricultural GDP in Bangladesh is projected to be 3.1 per cent less each year as a result of climate change. Bangladesh is a disaster-prone country, and, is often at the mercy of natural calamities.