BLOG | What have we learned about climate change, migration and adaptation in deltas?

By Robert Nicholls, Principal Investigator, DECCMA

Back in 2013 a multi-disciplinary consortium came together, comprising economists, engineers, hydrologists, modellers, demographers, economists, lawyers and social scientists from 11 countries. Our interest was the future of deltas under climate change. 

As dynamic systems that are highly sensitive to changes in the catchment and the marine environment, we know that sea-level rise will play a key role in shaping the future of deltas.  Deltas are home to 500 million people worldwide, concentrated in mid and low latitudes in the global South, and with significant numbers of poor residents. The capacity to adapt to those changes is unknown, and there are potential implications of sea-level rise for migration which are widely discussed, but little studied. Our motivation with DECCMA was to analyse the impacts of climate change, migration and adaptation in four major deltas: the Ganges-Brahmaputra-Meghna delta, with the bulk in Bangladesh and part in India (where it is termed the Indian Bengal delta), the Mahanadi delta in India and the Volta delta in Ghana.

Just over five years later, we have many insights into deltas that constitute new knowledge. This comes from multiple sources of evidence: we have conducted biophysical analysis and risk mapping, developed macro-economic models and scenarios to analyse how environmental shocks and change affect economic output and employment, compiled inventories of documented adaptations, reviewed governance and policy, undertaken surveys with men and women in over 5000 households and investigated multiple dimensions of well-being and the lived experience of migrants in cities of the deltas.

Climate change and sea-level rise are providing additional stresses to deltas, which are already experiencing coastal erosion, flooding and salinization due to climate variability, subsidence (deltas sink) and the consequences of upstream changes such as dams.  The amount of sea-level rise depends on how rapidly the earth warms, and by how much.  Based on current trends, we may see an increase in global average temperature of 2oC by 2033, which will bring an increase in sea level of between 5 and 14cm.This may seem a small amount, but it enhances the likelihood of flooding. In Bangladesh, the centre and northeast of the country will be most adversely affected due to the absence of structural adaptations in the form of polders. However, where livelihoods are concerned it is not just too much water that poses a risk to delta residents and salinization in the dry season is a big problem in India and especially Bangladesh, and this is enhanced by sea-level rise. In Ghana the challenge of drought arose as a key concern – one that is not typically associated with the delta and thus not necessarily targeted with agricultural adaptations.

Analysis has also provided more nuanced insights into the economic structure of deltas. Traditional reasoning is that deltas are densely populated due to high fertility enabled by sedimentation, which leads to high levels of agricultural production. Whilst agriculture is the major contributor to employment within all the deltas that we studied, it is not the sector that contributes most significantly to GDP. Instead the biggest economic contributions come from services and trade and transport. Further, all the delta economies are transforming and by 2050 will almost certainly be much larger than today. Agriculture will remain vital to food security and livelihoods but will be a smaller part of the economy and employment.

Recognising the nature of the economy raises questions around the nature of adaptations that will be required to reduce adverse effects of climate change. Agricultural adaptations are commonly observed at household level across all deltas. However, cumulative loss of GDP by 2050 is as high, or higher, in infrastructure than agriculture. Whilst agricultural adaptations therefore may be important to maintain socio-economic well-being among residents, infrastructural adaptation also needs to be considered by government to prevent economic losses and not hinder the large economic growth that is occurring.

People have typically adapted to the dynamic delta environment through mobility – moving to new areas when required to follow their aspiration for a better life - including both seasonal and permanent migration.  In particular a trend for movement from rural to urban areas exists and there are large growing cities in or near all the deltas. Climate and environmental change places additional stresses on people – but will likely perturb the existing migration system, rather than creating significantly new migration flows. Contrary to the “climate migrant” discourse, climate and environment are proximate causes of migration – altering the ability to earn a living and creating additional economic reasons to move.

Our analysis shows that migration patterns are strongly gendered. Although men move than women, the difference is decreasing over time. The places to which they go also differ, reflecting the gendered nature of the job market. In the Indian Bengal delta, for example, men tend to move to peri-urban areas, where they find employment in the construction industry; whilst women move to the centre of the cities for jobs as domestic workers and child carers.

We have observed a “blind spot” around migration in the countries in which we have worked. Failure to recognise the current and likely future nature of the phenomenon means that policy frameworks are often inadequate to support both voluntary migrants and displaced persons.

In short, the deltas of the future will look very different to the deltas of today. DECCMA’s research has added significant nuances to our understanding of the nature of environmental stresses and how they will change and the consequences for migration patterns, and adaptation needs under climate change. Through relationships built with policy-makers in Bangladesh, India and Ghana, we have already had the opportunity for our research to inform policy. The recently-released Odisha State Action Plan on Climate Change 2018-23, for example, has a chapter on gender for the first time; and Ghana’s new Coastal Development Authority is now guaranteed to have two representatives of the scientific community on the board.

What do these findings mean more broadly for delta management? Our research reiterates the importance of adaptive delta planning. This has been adopted in several developed countries, especially the Netherlands, and is enshrined in the Bangladesh Delta Plan 2100, in which the DECCMA Bangladesh leaders provided useful feedback from the project during the formulation process. Adaptive planning enables integration of planning across sectors and provides scope for flexibility and learning, which is essential to a sustainable future for these dynamic environments. 

For outputs from the DECCMA project, please visit An accessible summary is available in the publication “Climate change, migration and adaptation in deltas: Key findings from the DECCMA project” and a book will be forthcoming in 2019.