This paper considers two current challenges in the governance of maritime transport, specifically container shipping. The first is the oligopolistic market structure of container shipping, the downsides of which became evident during the COVID-19 pandemic. The second challenge is climate change, both the need to reduce emissions to zero by 2050 and to adapt to effects that are already locked in. The paper reviews the academic and policy literature and unveils a link between these market and environmental challenges which result from a focus on efficiency without considering negative effects such as diseconomies of scale and induced traffic, leading to a continued rise in total industry carbon emissions. The review likewise identifies links in how policy-makers react to the two challenges. Regulators could remove anti-trust exemptions from carriers, and policy-makers are being pushed to provide strict decarbonisation targets with a coherent timeline for ending the use of fossil fuels. Recent thinking on ecological economics, degrowth and steady-state economics is introduced as the paradigm shift that could link these two policy evolutions.