The urban boom in Cambodia's Phnom Penh is literally built on 'blood bricks' – an industry relying on a form of modern slavery, with a multigenerational workforce of adults and children trapped in debt bondage.

It's called one of the most climate-vulnerable countries in the world, with good reason. Cambodia relies heavily on agriculture, which is exposed to and affected by extreme weather events. In 2016, for example, 2.5 million people were affected by drought – the worst in a quarter century.

To cope with the destructive impacts of climate change, farmers take up loans which they struggle to repay. Eventually loans become unsustainable, and they are forced to leave their homes with their families and seek work where business is booming – the capital city of Phnom Penh. Cambodia is one of Asia's fastest growing economies, and the Phnom Penh skyline is rapidly growing with office blocks, housing estates, factories and shopping malls. But for the families arriving from the countryside, a poverty trap awaits.

Research funded through the ESRC-DFID Joint Fund for Poverty Alleviation Research has explored how the urban boom is literally built on 'blood bricks' – an industry relying on a form of modern slavery, with a multigenerational workforce of adults and children trapped in debt bondage. Kiln owners offer to repay farmers' debts and provide a consolidated loan. But in return, farmers and their families are trapped in a debt bond until the loan is repaid.

“The research has strengthened awareness of the connections between climate change and severe forms of labour exploitation,” says Professor Katherine Brickell, lead researcher for the project. “It has contributed to a deepening understanding of how climate change has exacerbated vulnerability in rural areas, in a context where millions of rural farmers across the global South are leaving agriculture and moving to urban work.”

Low brick prices and even lower levels of regulation mean that workers' pay is miniscule, typically at a piece rate of approximately £0.005 per brick for the whole team of workers involved, often up to 20 people or more. Workers are also prevented from leaving kilns to find other work when brick-making dies down in rainy months, forcing them to borrow more from kiln owners for daily spending in this period. As a result, families are forced to keep working at the kiln for years, or even for the rest of their lives.

“We have to work here because of debt; if not we would have decided to leave this place long ago,” says Kosal, a debt-bonded brick worker. “If the owner permitted, all of us would go back home because of our hard work. People prefer to rent land for growing rice or vegetables. But as for us, we're in debt so we can't do these things.”

Researchers from Royal Holloway, University of London and from the Royal University of Phnom Penh interviewed brick kiln workers labouring under conditions of modern slavery and construction industry informants. These qualitative interviews were combined with other data gathering, including a quantitative household survey and interviews in villages were people had emigrated to work on the brick kilns, geographic information system (GIS) mapping of water and topography in villages with high levels of migration to kilns, and analysis of longitudinal secondary data from the National Institute of Statistics.

The research reveals the combination of factors that lead to 'blood bricks' debt bondage – including the impacts of climate change, lack of state support for agriculture, lack of social protection or affordable health services, a largely unregulated microfinance sector, and the lack of accountability or transparency among global corporate companies investing in Cambodian construction.

“The research has offered policy recommendations to a number of actors,” adds Professor Brickall, “including the Royal Government of Cambodia, the United Nations Sustainable Development Goals, and the UK government with regards to strengthening the Modern Slavery Act 2015.”