Land degradation due to climatic variations and human activities is likely to pose a severe threat to sustainable agriculture, said experts at a seminar in Dhaka on the occasion of World Day to Combat Desertification and Drought on Tuesday. About 6 million hectares of the total geographical area of Bangladesh are degraded every year to varying degrees because of natural and manmade hazards such as river erosion, soil salinity, water logging and drought which are likely to hamper sustainable production for an increased population, they said at the national seminar on