In spite of all the debates and controversies, a global consensus has been reached that climate change is a reality and that it will impact on food production systems, among others, in diverse manifestations ranging from increased global temperature, to sea level rise, to more frequent occurrence of extreme weather events, to change in weather patterns such as the monsoonal rain patterns. In this regard, aquaculture is no exception. Aquaculture – farming in the waters – is also characterised by the fact that the organisms cultured, the most diverse of all farming systems, are all poikilotherms. It occurs in fresh-, brackish- and marine waters, and is spread across all climatic regimes from temperate to the tropics. Consequently, there are bound to be many direct impacts on aquatic farming systems brought about by climatic changes. The situation is further exacerbated by the fact that certain aquatic farming systems that also happen to be significant in commodity value, such as salmonid and shrimp farming, as well as those of relatively low commodity value but undergoing increasing intensification, are dependent, to varying degrees, on products, subjected to reduction processes, from the wild. All of the above factors will impact on aquaculture in the decades to come and accordingly, the aquatic farming systems will begin to encounter new challenges to maintain sustainability.

The challenges that aquaculture will face will vary to a significant degree between climatic regimes. In the tropics, the main challenges will be encountered by those farming activities that occur in deltaic regions, which also happen to be hubs of aquaculture activities, such as in the Mekong Delta and the Red River Delta in Viet Nam and the Ganges-Brahamaputra Delta in Bangladesh. Aquaculture activities in tropical, deltaic areas will be mostly impacted by sea level rise, and hence increased saline water intrusion and reduced water flows, among others. Perhaps, as a mitigating measure there could be a need to shift to more salinity-tolerant species or to develop higher salinity-tolerant strains, as the case may be. Elsewhere in the tropics, inland cage culture and other aquaculture activities could be impacted upon by extreme weather conditions, increased upwelling of oxygen poor waters in reservoirs, etc., requiring greater vigilance and monitoring, and even perhaps readiness to move the operations to more conducive areas in a water body.

Other indirect impacts of climate change on tropical aquaculture could be manifold and perhaps largely unknown. The reproductive cycles of a great majority of tropical species are dependent on the monsoonal rain patterns, which are predicted to change. Consequently, irrespective of whether cultured species are artificially propagated or not (the great bulk are), the change in the reproductive cycle will impact on seed production and thereby, the whole grow-out cycle and modus operandi and management of farm activities. Equally, such impacts will be felt on the culture those species that are based on natural spat collections, such as molluscs.

In the temperate region, global warming could raise the culture temperatures of some species to the upper tolerant range and thereby make such culture systems vulnerable to high temperatures, the mitigating measures available being either to shift to other species with high temperature tolerance and/or to develop strains tolerant to higher temperatures. In the temperate regions, there is a high possibility of new or dormant pathogens becoming virulent with increase in water temperature, confronting the sector with the need to combat new or hitherto un-manifested diseases.

Climate change may also cause indirect effects on aquaculture via impacts on production of those fish species that are used for reduction and which, in turn, form the basis for feeds in aquaculture, particularly for cultured carnivorous species. This is likely to have a major impact on some key aquaculture practices, spread across all climatic regimes. Limitations of supplies of fishmeal and fish oil, and the resulting expected exorbitant price hikes of these commodities, will lead to more innovative and pragmatic solutions on ingredient substitution of aquatic feeds, which perhaps will be a positive result arising from a dire need to sustain a major sector.

The sector has to be proactive and start working on adaptive and mitigating measures, sooner rather than later. Adaptive and mitigating measures to sustain the sector in the wake of climate change impacts will entail both technological and socio-economic approaches. The latter will be more applicable to small-scale farmers, the great bulk of producers in developing countries who constitute the backbone of the sector, contributing perhaps in excess of 70 percent of the global aquaculture production. The sociological approaches will entail the challenge of mitigating the potential climate change impacts on small farming communities, in the most vulnerable areas, such as in deltaic regions, and weighing the most feasible adaptive options and bringing about the policy changes required to implement those adaptive measures economically and effectively.

Global food habits have changed over the years. We are currently in an era where food safety and quality, backed up by ecolabelling are paramount; it was not so 20 years back. We will in the very foreseeable future move into an era where consumer consciousness will demand that farm foods of every form, when they reach the table, should have a minimal green house gas (GHG) emission level; the price and demand will be determined by such a factor. Perhaps the greatest challenge faced by aquaculture is to meet these aspirations, and even as it is today, to impress upon the public that the great bulk of aquaculture produce, for example about 70 percent of all finfish and almost 100 percent of all molluscs and seaweeds are minimally GHG emitting, and to continue the trend to drive aquaculture as the most green house gas friendly food source that is before us, and that the sector could still conform to such needs and continue to meet the increasing foodfish supply needs of the globe.