Tropical mega delta systems

I recently had the opportunity to chair a session on nature-based solutions at the Climate Exp0. It was a highly productive session with diverse ideas on how we might utilise nature and our interactions with nature to offer solutions to some of our most challenging environmental, economic and social issues linked to climate change. Examples include reforestation at a large tropical forest scale and in Kenyan communities, to the role that natural landscapes can play in flood management in the UK.  It got me thinking about addressing some key issues within climate change beyond building a wall for flooding or a reservoir for drought.  Indeed, when the Nutrition Society invited me to speak at the forthcoming Summer Conference 2021 (6-8 July 2021 - online) on the subject of changing the world's food production techniques. I decided to focus on some of the work that myself and colleagues across the globe have been doing for the past 10 years regarding how food production might be conducted in changing landscapes in some of the world's largest deltas, and nature-based solutions might address some of these issues.

Indeed, the University of Southampton currently leads on a series of large interdisciplinary projects on tropical mega delta systems such as the Ganges, Brahmaputra, Meghna Delta (GBMD), spanning Bangladesh, India Vietnamese Mekong Delta (VMD). These deltas are often cited as food production centres with local, regional and international significance, and I hope that in this talk I can highlight specific elements of this work that both elucidate how the transitioning of the delta landscapes to high-intensity production, combined with environmental changes are driving some destructive demographic changes and causing unplanned migration and unsustainable urbanisation. This might then form the basis for some thoughts on what nature-based solutions we might consider to address some of these issues. The following is the abstract I have put together that lays out the content of that talk.

Deltas are sometimes called the breadbaskets of the world, or more appropriately, the rice baskets.  These flat, easily cultivated systems are fed by sizeable international river systems draining the Himalayas, bringing vast quantities of sediments that act as fertiliser for highly productive soils. Mega deltas such as the GBM and VMD face multiple challenges, including urbanisation, industrialisation, and substantial environmental changes, including climate change, salinisation, rising sea levels, increased storminess, and floods' twin challenges droughts along with increased food demand for domestic and export markets. The GBMD, like the VMD, has historically been dominated by the production of rice, often in small to medium farms with relatively low productivity based upon high levels of cheap available labour and a semi-subsistence model of production. Recent environmental, food security and economic policy-based decisions have highlighted the need for investment in the landscape to maintain and protect production as well as diversification to agricultural practices to enhance efficiency.  In areas not lost to salinity or flood and erosion, these investments raise the land value, require higher returns and drive efficiencies that see farm labourers replaced by modern farming practices. In Bangladesh and particularly Vietnam, single cropping is progressively replaced by triple crop rice that, whilst being protected from periodic dangerous flooding behind embankments, also requires expensive irrigation, fertilisers that deplete the soils and pesticides that are ecologically destructive in order to replace flood-based natural ecosystem services. In Bangladesh, there is a substantial and progressive transformation from rice production, nominally in response to increased salinisation, but predominantly to support a highly lucrative shrimp industry that is destructive of the landscape and offers a very low level of local employment.  These processes culminate in the migration of landless poor out of the rural delta and into urban centres where they often compete for opportunities in factory-based production or provide cheap transport such as rickshaw pulling or the building sector.

So how might we react to these economic and environmental forces that drive the poorest sectors of the population out of the rural areas and into the cities? In the simplest sense, we need to recognise that migration to cities can be a highly productive thing. Where there is good quality work, urban environments can efficiently manage ever-growing populations and provide hitherto unavailable access to health and education. However, when that migration is imposed by land-use change and or severe environmental change, the migration can become unplanned with large populations arriving in urban areas poorly equipped to cope.  Currently, the adaptions that have been put in both deltas to arrest the impacts of climate change and the inadvertent impacts of environmental change through such interventions as dams and urbanisation have focused upon embankments, levees and walls. Nature-based solutions would encourage us to consider solutions such as mangrove forest reforestation. These too, can slow the progress of storm surges, sea level rise, as can concrete constructions. However, mangrove forest can also provide habitats for biodiversity and livelihoods for the poorest sectors of the rural communities, including fishing, honey collection, and ecotourism.  Likewise, large scale and short-lived shrimp farms, sometimes suggested as adaptions to increased salinity in deltas, prove to be a maladaptation. They take away rice-based livelihoods and employ very few people and intoxicate the soil before moving on to another area. However, ancient practice merges shrimp farming with rice production and other fish-based aquiculture to produce an agriculturally productive ecology linked to the river systems' natural flooding cycles. This system, which is well established in some areas of Vietnam,  benefits from fish fertilising the rice, keeping pests under control, and sustaining a river and field-based fishery through natural re-stocking. Of course, nature-based solutions' production level and efficiency can rarely compete with the industrial, agricultural process of intensive farming. However, such methods are known to destroy the soil they are practised on and drive out the poor from their ancestral livelihoods. Sustainability is about the longer term, and with as much as 50% of food produced being wasted, can we not find a way to think again and allow at least some partnership with nature. Rightly this broad approach will be a crucial feature of COP26.

Professor Craig Hutton, Professor of Sustainability Science, University of Southampton

Find Out More