It’s widely agreed that one of our greatest global environmental challenges is the impact of fisheries on the oceans. Aquaculture, practiced at a small scale around the world and especially in Asia for centuries, emerged decades ago as a potential solution. But it soon became clear that aquaculture was using more wild-caught fish as feed (as an input), than it was generating as product. In other words, it was making the situation even worse. However, things have changed in the way that we manage this final frontier of agricultural intensification. And this story is not all about the ocean. Mariculture - marine aquaculture - supplies more than 50% of the world’s seafood, but the freshwater aquaculture is even larger than the mariculture industry. Aquaculture is a big deal.I spoke about this subject with economist Roz Naylor, a professor of earth system science at Stanford University's Center for Food Security and the Environment. She led a seminal review to examine the "Effect of aquaculture on world fish supplies", which was published in the journal, Nature, in 2000. Twenty years later she led the publication of "A 20-year retrospective review of global aquaculture", again in Nature. Both papers took an exhaustive look at all the literature available at the time, to piece together comprehensive narratives that outlined the pros and cons; the advances and obstacles of one of humankind's most important and promising food systems, and its impact on the environment.Time stamps:2:10   What is aquaculture - what does it include?2:57   Where is most aquaculture happening?5:30   The many species used in aquaculture and how they are used.10:16  Roz’s interest in aquaculture, as an economist.12:25  How aquaculture became more sustainable, and related trade-offs20:58   Technology that has improved aquacultural production and sustainability27:53   Aquaculture species’ energy conversion efficiency29:33   The potential and limitations of "extractive species"34:57   Integrated multi-trophic aquaculture37:32   Future promise of aquacultureVisit www.case4conservation.com