The challenges of safely navigating the evolution of the food-energy-water nexus demand that fishing in rivers and seas is done without upsetting nature’s checks and balances
The impact of dams on fish diversity is a telling example of unintended consequences and cascades of human activities. It is also true that while aquaculture may complement yield of fisheries, enhance food security and bring in export income, it exacerbates coastal vulnerability by decimating mangrove forests. Combined with all the other global warming impacts, India may be facing a veritable field of landmines full of dammed-if-you-do and dammed-if-you-don’t scenarios in managing its food-energy-water nexus.
An excellent window into some potential pathways for such cascades is offered by a recent study by Ashoka Trust for Research in Ecology and the Environment (ATREE), a Bangalore-based research organisation. The researchers studied the impact of hydrological barriers such as dams on the diversity of fish. This comes on the heels of several reports that agriculture and aquaculture are among the major contributors to the loss of mangrove forests around the world.
India and Bangladesh are obviously a part of this pattern of mangrove forest loss. It is noteworthy that India is second only to China in aquaculture, with yield of over four million tonnes per year. The ecosystem services of mangrove forests are widely quantified and documented in terms of the rich habitats they provide for a large number of species, their role in sequestering carbon while serving as natural defences against storms and coastal erosion.
Land change activities like building dams and other hydrological barriers also affect the mangrove forests by choking off the sediment loading while increasing nutrient pollution. Even well known benefits of a system like the mangrove forests does not mean their protection will be automatic vis-à-vis all other socioeconomic and political or even environmental choices.
The ATREE study focused on the impact of dams on the recovery of fish diversity or the number of species by comparing the species composition upstream and downstream of a dam. Species composition would anyway depend on the location along a river since some fish prefer fast flowing waters while some are more adept at living in more varied environmental conditions. In addition, other activities such as agriculture, deforestation and urbanisation may also affect species distribution.
The study separates all factors to extract the impact of the hydrological barriers alone. It finds that the impact on the number of species is largest immediately downstream of a dam while the recovery further downstream is enhanced by an increase in the amount of dissolved oxygen in the water. On the other hand, the recovery is affected due to an increase in alkalinity of the water.
The main message of the study is that reducing the number of dams, barrages or other barriers increases the potential for species recovery. While this may sound intuitive, it does offer guidance for managing watersheds to sustainably navigate the food-energy-water nexus.
As the old saying goes, nature makes the rules and biology finds the loopholes. One study does not a decision make. More studies are clearly needed to identify the mobile generalist fish species that are more resilient to habitat perturbations and hydrological barriers and to explore whether any novel genetic approaches can be brought to bear on transferring their resilience to the sedentary specialists that are more vulnerable.
Considering the challenges of safely navigating the future evolution of the food-energy-water nexus, our own resilience clearly depends on making the fish more resilient to our actions as well as farming food and fish without destroying the mangroves.
It is impossible to find any discussion on global sea level rise due to climate change without a mention of the Ganga-Brahmaputra Delta and the vulnerability of Bangladesh to sea level rise. The other oft-mentioned trend is the rapid and monotonic warming of the Indian Ocean. However, it is now known that the sea surface temperature warming is more rapid over the western Arabian Sea than elsewhere over the tropical Indian Ocean.
It has also been reported that sea level rise is occurring at around 5 mm every year, nearly twice the global rate, along the east coast of the Bay of Bengal during the past 25 years or so. Another study argued that the warming over the Bay of Bengal is damped since about 1995 by an increase in depressions and cyclones. The caveats are of course that natural variability could be affecting sea level rise while the warming of the Bay of Bengal may in fact require an increase in heat loss due to convection and cyclones because the sea surface temperatures are already near the threshold for atmospheric deep convection.
The debate over the Indian Ocean is also confounded by a downward trend in the seasonal monsoon rainfall with a multi-fold increase in extreme events and complicating influences of aerosols that are likely leading to the failure of climate models in capturing the historic trend in monsoon rainfall or delivering reliable future projections on the fate of the monsoon.
Reducing marine productivity
Worse yet, a reduction in marine primary productivity is observed for several decades over the Indian Ocean and this is also manifest in reduced fish yield. This reduction in fish yield can affect food security of the Indian Ocean rim countries some of which are embroiled in civil conflicts, piracy, etc.
India also faces contradictory issues in terms of a burgeoning middle class seeking more and more protein from meat and fish. The global demand for high-value fisheries products like shrimp is also driving up aquaculture investments in India.
Fisheries in India have grown more than 10 times since independence and have had a robust growth of 10% in parallel with recent economic growth. Fisheries’ contribution to GDP of around 1% may seem low, but it does not account for the overall impact in terms of employment of over 15 million people. Nearly a third of the economic value of fisheries is from exports.
High potential for exploitation
India’s 8,000 km coastline and the extensive river system offer a very high potential for aquaculture and its exponential growth in the last two decades indicates that the potential will be fully exploited in the coming years and decades. Aquaculture now contributes nearly 50% to the total fish production of over 10 million tonnes per year, which can be expected to grow mainly due to fishing effort and aquaculture rather than increased marine and freshwater fish yield.
Contributing factors to increased fish yield include the advances in Potential Fishing Zone forecasting at Indian National Centre For Ocean Information Services (INCOIS), which not only help artisanal and subsistence fishermen with their livelihoods but also assist industrial fisheries. The demand in the domestic market is not as steady as the export market due to affordability and access issued among Indian population as well as due to externalities such as the lack of refrigeration facilities and efficient supply chains which affect availability.
Traditionally, India’s average annual per capita fish consumption of 5-8 kg stands at 50% of the global levels. But the growing consumption patterns are highly correlated with income levels and demand can be expected to continue to grow.
Given these multitudes of issues, it is an opportune time to focus on the unintended and unexpected cascades in the natural-human interactions in the food-energy- water nexus. Climate change effects such as sea level rise, fisheries and aquaculture, as well as water and energy demands interact in unforeseen ways.