The modern world has long thought of refugees in strictly political terms, victims in a world riven by competing ideologies. But as climate change continues unabated, there is a growing population of displaced men, women and children whose homes have been rendered unliveable thanks to a wide spectrum of environmental disasters.
Despite their numbers, and their need, most nations refuse to recognise their status. The 1951 UN Convention relating to the Status of Refugees defines a refugee as a person with a genuine fear of being persecuted for membership in a particular social group or class. The environmental refugee - not necessarily persecuted, yet forced to flee - falls outside this definition.
Where the forest used to be, torrential rains bring barren hills of mud down on villages. Crops wither in the parched earth. Animals die. Melting glaciers and a rising sea swallow islands and low-lying nations, flooding rice fields with salt water. Factories spew toxic chemicals into rivers and oceans, killing fish and the livelihood of generations. So people flee. Many become internally displaced, others cross any and all borders in order to survive.
Experts at last year's annual meeting of the American Association for the Advancement of Science estimated that their numbers would reach 50million by 2020, due to factors such as agricultural disruption, deforestation, coastal flooding, shoreline erosion, industrial accidents and pollution. Today, it is believed that the population of the environmentally displaced has already far outstripped the number of political refugees worldwide, which according to the UN High Commissioner for Refugees is currently around 10.5million.
Still, accurate statistics are hard to come by. Because the term "environmental refugee" has not been officially recognised, many countries have not bothered to count them, especially if the population is internally displaced. Other countries consider them migrants, and therefore beyond the protection granted refugees.
Another factor obscuring the true scope of the population is that their numbers can rise quite suddenly - such as after the Fukushima nuclear disaster last year, or Haiti's 2010 earthquake, which displaced some 1.5million people - which makes accounting for their number difficult if not impossible.
In 1999, the International Red Cross put the number of those displaced by environmental disasters at 25million. In 2009, the UN estimated that number to be 36million, 20million of whom were listed as victims of climate change-related issues.
Two decades ago, ecologist Norman Myers predicted that humanity was slowly heading towards a "hidden crisis" in which ecosystems would fail to sustain their inhabitants, forcing people off the land to seek shelter elsewhere. Hurricanes Katrina and Rita that hit the US proved that, no matter how wealthy or powerful, no country is impervious.
Indeed, being displaced by natural disasters may very well become the central epic of the 21st century. Kiribati, the Maldives and Tuvalu are disappearing as the sea level continues to rise. The World Bank estimates that, with a one-metre rise in sea level, nearly a fifth of Bangladesh - with a population of 152million - would be under water, resulting in millions of environmental refugees. Some have already fled to neighbouring India, where they face lives of misery and discrimination.
China, in particular, is a hot spot of environmental disasters as it buckles under unsustainable development, giving rise to rapid air pollution and toxic rivers. Alongside desertification, these man-made catastrophes have already left millions displaced.
John Liu, director of the Environmental Education Media Project, spent 25 years in China and witnessed the disasters there. He sounded this warning some years ago: "Every ecosystem on the planet is under threat of catastrophic collapse, and if we don't begin to acknowledge and solve them, then we will go down."
Yet, as the number of environmental refugees increases, the work for their protection is falling behind. While a political refugee is given some modicum of protection, often those who flee their environmentally devastated homeland are seen as mere migrants. When US President Barack Obama granted temporary protected status to undocumented Haitians living in the US in the aftermath of the earthquake in Haiti, it was a baby step in the right direction for human rights.
Policies should also include addressing the issue of reforestation and rehabilitating degraded land and soils, as well as addressing the desalination of coastal areas. Those involved in man-made environmental devastations - illegal mining, toxic dumping and oil exploration - should be held fully accountable in international court and be held responsible for the resettlement and compensation of those they displaced.
"One of the marks of a global civilisation is the extent to which we begin to conceive of whole-system problems and whole-system responses to those problems," political scientist Walt Anderson wrote in his book All Connected Now. "Events occurring in one part of the world are viewed as a matter of concern for the whole world in general and lead to an attempt at collective solutions."
Whether humanity can move towards a global civilisation will depend by and large on how it can act collectively to deal with climate change and the resulting human displacement.
There's an old saying that "a rising tide lifts all boats". In the age of melting glaciers, that tide is an ominous threat. The global age will not be as golden as some had predicted unless this dire challenge is met. For, rising tides will not just send more refugees fleeing but, if ignored, could swallow humanity itself.
Andrew Lam is an editor with New America Media and the author of Perfume Dreams: Reflections on the Vietnamese Diaspora, and East Eats West: Writing in Two Hemispheres. His next book, Birds of Paradise Lost, is due out in 2013