The study shows that while migration is increasingly recognised as an effective way to deal with climate risks, or a form of adaptation, it is far from a silver-bullet solution.

For example, remittances -- which include flows of money, ideas, skills and goods between migrants and their places of origin -- are thought to be key to facilitating adaptation to climate change.

But, drawing on evidence from every continent for the past decades, this research shows that while remittances help improve material well-being for families and households in places where migrants move from, this often comes at a cost to the well-being of migrants themselves.

For example, migrants in Bangladesh are not sufficiently considered in planning and policy and remain excluded from urban structures and services.

This has repercussions for all aspects of their everyday lives in urban destinations such as living conditions, income security, and eventually their ability to keep supporting their families back home.

Dr Lucy Szaboova from the University of Exeter, the study's lead author, said: "The idea of migration as adaptation places the responsibility of predicting and responding to future risks on individuals, and could justify policy inaction.

"This is problematic, because where migration is not met with appropriate policy support, it can reinforce vulnerability and marginality and ultimately jeopardise the success of adaptation."

Tensions in well-being, equity and sustainability

The study found that migration often leads to tensions within and between well-being, equity, and sustainability. These tensions can create winners and losers.

Experiences of migration as adaptation are not equal for everyone involved.

Depending on the context and on people's social characteristics such as age, gender, ethnicity, for instance, migration can have different outcomes for different people.

Some might benefit while others lose out.

For example, the household overall may be financially better off thanks to remittances from the migrant, but female household members whose work burden increases with men's migration, may be struggling to maintain the farm and must make tricky choices that can eventually undermine the success of migration as adaptation.

Dr Mumuni Abu, from the Regional Institute for Population Studies at the University of Ghana, said: "In the absence of equity, migration can exacerbate rather than reduce vulnerability to climate change.

"For example, in rural places of origin, constraints on gender equity between men and women at the household and community level, often result in the unsustainable use and management of natural resources."

Dr Amina Maharjan, of the International Centre for Integrated Mountain Development (ICIMOD), added: "Remittances are often lauded for their potential to support development and adaptation, but experiences point to the need to consider their role along longer time horizons."

Indeed, the implications of migration for the success of adaptation often unfold over extended timescales, including across different generations.

Creating an enabling policy environment

The authors suggest that evaluations of the success of migration as adaptation should, therefore, take into account outcomes for migrants, their households and family members in places of origin, and for the host society.

They should also recognise that some implications might not be immediately obvious but might unfold over longer timeframes.

To address tensions that can stand in the way of success, migration as a plausible adaptation option should be made visible in policy and planning.

Drawing on extensive research with migrants and policy and planning stakeholders in urban migration destinations, Professor Neil Adger from the University of Exeter highlighted potential solutions for creating an enabling policy environment.

"Migrants in cities are disproportionately exposed to social and environmental hazards which negatively affect their health and wellbeing," he said.

"Despite this, they remain largely invisible and voiceless in policy circles.

"Participatory urban planning and deliberative approaches can support the inclusion of diverse perspectives on building safe, sustainable and resilient cities and can support migration as successful adaptation."

The paper, published in the journalOne Earth,is entitled: "Evaluating migration as successful adaptation to climate change: trade-offs in well-being, equity and sustainability."

It is the outcome of collaboration between researchers from the University of Exeter, University of Vienna, University of Ghana, the London School of Economics and Political Science, and the International Centre for Integrated Mountain Development (ICIMOD).

This research was funded by Canada's International Development Research Centre (IDRC).