This article was originally published in the Journal of International Humanitarian Legal Studies, vol. 1, 2010
It took one of the world’s deadliest disasters, the tsunami of 2004, to bring home to governments and policymakers around the world the need to develop more effective responses to natural disasters and the people uprooted by them. Five million people were displaced and some 250,000 killed in 11 different countries in Asia and Africa. Even today, six years later, reconstruction efforts are ongoing, while the impact on infrastructure, clean water, sanitation, and livelihoods is expected to last for decades.
The tsunami was caused by an earthquake, not climate change, but floods, hurricanes, cyclones, landslides and other ‘sudden-onset’ disasters are expected to become more frequent and severe in the future as a result of climate change. Over the past two decades, the number of recorded disasters has doubled from approximately 200 to over 400 per year; and nine out of 10 disasters have been climate-related. The total number of people affected by natural disasters over the past decade has reportedly tripled to two billion people, an average of more than 200 million people directly affected each year.
The increase in natural disasters is expected to produce massive displacement that will change the world’s perception of forcibly displaced people, currently thought of primarily as refugees and internally displaced people (IDPs) uprooted by persecution and conflict. The vast majority will be displaced inside their countries, although significant numbers will cross internationally recognized borders, especially when island States become submerged. Although estimates of the numbers of those displaced will vary, a 2007 Christian Aid report estimates that between 2007 and 2050, “climate change-related phenomena” (floods, hurricanes, drought) will “permanently” displace 250 million people. The United Nations and the Internal Displacement Monitoring Centre (IDMC) find that while they cannot predict whether the people involved will be permanently or temporarily displaced, in 2008 alone some 36 million people were uprooted by sudden-onset natural disasters, including 20 million displaced by disasters associated with climate change.
If one were to add to these numbers those compelled to leave their homes by longer-term environmental problems (e.g. drought, desertification, rising sea levels, extreme temperatures, deforestation, land degradation), known as ‘slow-onset’ disasters, the total for 2008 would undoubtedly be tens of millions more. The UN/IDMC report cites a figure of 26.5 million drought-affected persons in 2008, but no overall estimate exists of those displaced by slow-onset disasters. Traditionally, migration from such disasters has been perceived as ‘voluntary’, but increasingly such movement is also being seen as ‘forced.’ Indeed, long-standing international definitions of forced migrants and the international systems of protection for them may have to expand to accommodate the many different patterns of migration emerging.
 United Nations Environment Program, GEO Yearbook 2004/2005, http://www.unep.org/geo/pdfs/GEO%20YEARBOOK%202004%20(ENG).pdf (last accessed 17 February 2010).
 J. Holmes, ‘The Need for Collaboration’, 31 Forced Migration Review 4 (2008), at 4.
 IFRC, World Disasters Report 2002: Focus on Reducing Risk, at Introduction, http://www.ifrc.org/publicat/wdr2002/intro.asp (last accessed 17 February 2010).
 The overall estimated total number of IDPs uprooted by conflict is 26 million; the refugee total is 10.5 million plus 4-5 million Palestinian refugees. See Internal Displacement Monitoring Centre, Global Overview of Trends and Developments in 2008 (April 2009), at 9; and UNHCR, 2008 Global Trends: Refugees, Asylum-Seekers, Returnees, Internally Displaced and Stateless Persons (2009), at 2. For varying perspectives on the issue of environmental displacement generally, see R. Black, ‘Environmental Refugees: Myth or Reality’, UNHCR Working Paper 34 (2001); S. Castles, ‘Environmental Change and Forced Migration: Making Sense of the Debate’, UNHCR Working Paper 70 (2002); E. Piguet, ‘Climate Change and Forced Migration’, UNHCR Working Paper 153 (2008).
 See, for example, the debates between ‘alarmists’ and ‘skeptics’ in S. Martin, ‘Managing Environmentally-Induced Migration’, in F. Laczko and C. Aghazarm (eds.), Migration, Environment and Climate Change 353 (2009).
 Christian Aid, Human Tide: The Real Migration Crisis (May 2007), at 6. Other estimates are lower, 150 million, see UNGA, Note by the Secretary-General, Protection and Assistance to Internally Displaced Persons, A/64/214, 3 August 2009, para. 11.
 UN OCHA and IDMC, ‘Monitoring Disaster Displacement in the Context of Climate Change’, 22 September 2009, at 9. For an analysis of the connection between climate change and displacement, see V. Kolmannskog, ‘Climate Change, Disaster, Displacement and Migration: Initial Evidence from Africa’, UNHCR Working Paper 181 (2009), at 6, 10; also Norwegian Refugee Council, ‘Climate Changed: People Displaced’, 8 December 2009, http://www.nrcfadder.no/arch/img.aspx?file_id=9913616 (last accessed 17 February 2010).
 UN OCHA/IDMC report, ibid.