A/67/299 climate change ranging from 50 to 250 million by the year 2050. 7 The Special Rapporteur remains aware, however, that accurate data on this issue is not readily available. Furthermore, he recognizes that statistical exercises will be controversial, not only in view of the difficulty in predicting the rate of sea level rise and its impact on persons, but also with regard to a key conceptual hurdle: the difficulty of identifying those migrants who can be said to have moved solely for reasons related to climate change. For example, it is difficult to isolate the effects of climate change that may contribute to population movements from other environmental factors, such as land degradation, which may be linked to other stresses on the environment, including the impact of an increasing global population consuming ever more natural resources. 32. In this context, the Special Rapporteur understands that although environmental transformations experienced as a result of climate change may contribute to migratory movements, environmental migration, like every kind of migration, is essentially a complex, multicausal phenomenon which may be driven by a multiplicity of push-and-pull factors. Thus, the question of identifying those who have migrated as a result of climate change might be a challenging, if not impossible, task: the impacts of climate change often contribute to a cluster of causes that lead to migration. 33. Further difficulties in defining the climate-change-induced migrant are compounded by the fact that climate change may induce a range of migration patterns. Climate change may induce temporary, circular and permanent migration movements, which may be multidirectional, or episodic. Persons affected may move internally or internationally, spontaneously or in an organized and planned manner, and may range on a wide continuum between forced and voluntary migrations. Future predictions remain problematic: while research may suggest some ways in which climate change may affect migratory patterns, it is difficult to predict future movements accurately if only because of the decisive role of individual human agency, as migration is always also an individual trajectory and never simply a mass displacement. Moreover, the success, or lack thereof, of future mitigation and adaptation strategies, including the development of new technologies which may or may not ameliorate the situation of those most affected by the effects of climate change, are impossible to know. Furthermore, it is impossible to forecast the impact of future extreme environmental events, including their regularity or force. 34. Notwithstanding, or perhaps in the light of these conceptual difficulties, the Special Rapporteur recognizes the need for more rigorous scientific, empirical, sociological, legal and other research in this field. Only with precise knowledge of the scope and nature of environmental migration will States be able to develop and agree upon common policies in this regard. 1. Identifying people vulnerable to climate-change-induced migration 35. While climate change may be felt across the globe, it is likely that its impacts will affect some individuals and groups more than others. At a global level, the Intergovernmental Panel on Climate Change reflected “sharp differences across __________________ 7 8 Nicholas Stern, Stern Review on the Economics of Climate Change, Cambridge, United Kingdom, Cambridge University Press, 2006, p. 77, describing 250 million as a “conservative” assumption of how climate-induced displacement is to be defined. 12-46071