More robust data and stronger legal protections are needed to better understand environmentally induced human migration and to respond to the tens of millions of people around the world who will likely flee their homes as a result of climate change over the coming decades, say several experts.

In the past few years, intense droughts and extreme storms have hit impoverished regions in South Asia, the Horn of Africa, Latin America and the African Sahel, highlighting the twined dilemmas of extreme weather and underdevelopment.

Academics and public policymakers wonder what impact environmental factors will have on peoples' decisions to migrate and how the public sector, nongovernmental organizations and intergovernmental agencies might best prepare for a potentially enormous movement of people.

Climate change-induced migration, experts point out, is already occurring on several scales. Displacement might come from an acute humanitarian crisis, such as a flash floods, or a slowly intensifying drought over many years. Migrants may relocate within a country or flee across national borders.

Koko Warner, head of the Environmental Migration, Social Vulnerability and Adaptation Section of the U.N. University, is exploring changing rainfall patterns, food security and human mobility in eight countries: Peru, Guatemala, Ghana, Tanzania, India, Bangladesh, Thailand and Vietnam.

Outlining preliminary research findings, she said that, up to now, informed policy discussions have been limited by a lack of understanding of what is actually occurring among migrants.

A knowledge void

"There's not very much data on stressors as well as mobility. So one of the contributions that we're trying to make is to start filling in some of the data," she said.

Warner's research aims to discern the conditions under which households migrate in order to manage rainfall extremes and food security.

"Do they migrate more? Do they migrate less? Can you find out something about who's migrating and why?" she said, explaining the report's objectives.

Working in partnership with the international aid organization CARE, Warner hopes the final report, which will be released in December, will help to bring services in a "meaningful way" to those displaced by rainfall extremes.

"Everyone is using migration," she said, "but in very different ways."

Migration might be part of a strategy for adapting to climate extremes, or it might be because of a lack of capacity to adapt, she said. It might be invoked, she added, as a means of improving a household's economic opportunities, following the collapse of a fishery or agricultural crop, for example, or as a means of survival after a catastrophic flood or persistent dry spell.

"As you move down this spectrum from resilience to urgent need, you start seeing migrants are heads of household. They're male. They leave ... to obtain food or to obtain resource to get food."

While those who are seeking economic opportunity often send remittances back to family members, which might improve a household's situation, the more desperate of them, she said, "survive, but they don't thrive."

'A last-ditch effort'

She added, "They survive another day, but over the years, their asset base deteriorates. Migration in some ways is a last-ditch effort."

Most vulnerable to environmental stress, she said, are those who live on the social and economic margins prior to migration, the "most highly precarious situations of any households that we surveyed."

But the picture emerging from the research, she said, provides policymakers and aid organizations with potentially rich insights.

"One of our lessons learned was that adaptation efforts that are meant to build the resilience of people really need good targeting mechanisms," she said. "Adaptation and resiliency happen across levels of society. It's very important to understand the needs of the people who are affected; there's a great need for targeting and more nuanced policy."

While Warner highlights the growing interest in how environmental factors are felt on the household level, other researchers express concern about the lack of legal protections for migrants on the national and international levels, particularly as global cooperation on climate change remains touch-and-go since the failed 2009 U.N. climate talks in Copenhagen, Denmark.

Roger Zetter said environmental stresses occur within the context of other political, economic and social considerations. On the national level, he said, legal protections for migrants are wholly out of sync with the challenges presented by climate change.

Zetter, an emeritus professor of refugee studies at the University of Oxford, surveyed migrants in five "archetypal countries" -- Bangladesh, Vietnam, Kenya, Ghana and Ethiopia -- to see "what's actually happening on the ground."

His primary concern is with "how people read the rights discourse, if you like, how they engage debates on rights, how they invoke issues of rights if they are being resettled by governments or if they can avail themselves to government compensation mechanisms."

In his research, Zetter said, he has found very little evidence at the local level that people are even considering rights protections. Where protections exist, they are often trumped by customary laws around gender or livelihood, for example.

A legal void

Local social norms, in other words, greatly outweigh the juridical heft of national law.

"I think what I found surprising is the fact that the issue of rights-based concerns doesn't appear to mediate [decisions on migration] at all on the local level," he said.

He added that these customary rights often stand in sharp contrast to national legal protections for migrants, setting up a "twin track."

On one hand, national laws might not have any implementation or buy-in from households on the local level, but on the other hand, the local customs that play a central role in decisionmaking on the local level may not adequately anticipate the intensity of environmental threats brought about by climate change.

"In none of these countries does one find a coherent response to internal migration and displacement," he said.

The key to changing this, he said, is a mix of thoughtful policy-setting and advocacy, including ending "turf wars" among national governments and intergovernmental bodies like the United Nations and holding rich countries accountable to agreements on climate change.

Walter Kälin, a former representative of the U.N. secretary-general on the human rights of internally displaced persons, adds another dimension to the problem of legal rights for migrants fleeing environmental stress: cross-border migration.

"Any kind of definition we have on refugees is based on the assumption that someone is turning against the people, and they have to flee. It's the state or non-state actors. It's about persecution in the narrow or broader sense, something we don't have in the broader context of [environmental] disasters," he said.

Human rights agreements, he added, are similarly out of sync with the category of international migration due to environmental stresses.

Several nations, including Norway and Switzerland, he said, are forming an alternative venue for building consensus on how to address climate change-induced migration.