ENVIRONMENTAL refugees represented the largest population movement in Asia in recent years, International Labour Organisation (ILO) experts told a conference in Darwin yesterday. Bangkok-based ILO researchers Dr Mando Abdella and Dr Lin Lean Lim said the creation of deserts affected an estimated 860 million hectares of land and 150 million people in Asia. Despite government programmes to stop it, deforestation had risen from an estimated two million hectares a year in 1980 to five million in 1990. ''Occurring almost unnoticed in many parts of Asia is the dislocation of millions of families every year as a consequence of desertification, land degradation and extensive reduction of biodiversity,'' they said. Dr Abdella and Dr Lim reported to the Australian Bureau of Immigration and Population Research conference on Asia-Pacific migration affecting Australia. They said land degradation as a result of logging and over-grazing was a serious problem throughout the region, with soil erosion affecting 1.3 million square kilometres in China and 37 million hectares of hillside in India. ''Distress migration due to environmental degradation is very difficult to measure,'' they said. It could be deduced from statistics on movement between countries and from country to city. For instance, in the past 20 years Nepal and Bangladesh, both severely affected by environmental degradation, had the highest urban growth in the region. Dr Abdella and Dr Lim also said the widening pattern of investment by Japan and Asia's newly industrialised nations, including Hong Kong, had led to the formation of an international labour market. ''Hong Kong and Singapore have increasingly resorted to outward processing, the former in Southern China and the latter in the Rio Islands of Indonesia. ''As these countries internationalise their economies and become key investors in Asia, they have created, knowingly or unknowingly, a transnational space for the circulation of goods, capital and culture, which in turn tends to create conditions for thecirculation of people and, in effect, the formation of international labour markets.'' As legal and illegal migrants flowed into those booming new economies, growing numbers of managers, professionals and other skilled workers accompanied capital out of Hong Kong, Japan, Taiwan and South Korea to the countries in which they were investing.