By Duarte, Carlos M Holmer, Marianne; Olsen, Yngvar; Soto, Doris; Marba, Nuria; Guiu, Joana; Black, Kenny; Karakassis, Ioannis

The human population is projected to reach 9200 million by 2050 (UN 2007), which is within estimates of the maximum carrying capacity of the planet (Cohen 1995). A fundamental question for science is whether it is possible to increase food production to meet the demands of a human population of that magnitude. There is little room for optimism.Available water resources appear insufficient for agriculture tomeet the food demands of 9200 million people (Cohen 1995, CAWMA 2007). The present population already experiences water stress (CAWMA 2007), which is exacerbated by the interactive effects of population growth and climate change (Vorosmarty et al. 2000). In addition, global fisheries landings have been declining since the mid-1980s (Pauly et al. 2003), contributing to the current food production crisis. Under this scenario, marine aquaculture (hereafter mariculture), the food- producing sector least dependent on freshwater availability (Verdegem et al. 2006), will be enlisted to help feed humanity in the 21st century (Marra 2005). Global terrestrial production and marine primary production are comparable in magnitude (Field et al. 1998), but marine food now contributes only 2% to the human food supply (FAO2006a), as the development of controlled food production in the ocean lags several millennia behind that on land (Duarte et al. 2007).Aquaculture production currently faces important challenges (Diana 2009) that may hinder its future development. Because large-scale domestication of the ocean should be a mainstay of the response to future food crises (Marra 2005), it is imperative to determine what is required to bring about this domestication. Here we build on recent analyses (Diana 2009) to examine the prospects for mariculture becoming a major force to meet growing human food demands, and we analyze the bottlenecks and challenges mariculture must overcome.

Source: Water World