ARE WE MISMEASURING ENVIRONMENTAL SUSTAINABILITY IN AQUACULTURE?
Aquaculture is widely promoted as a more environmentally sustainable solution to meet the growing global demand for animal protein when compared to terrestrial food systems. However, this narrative is often grounded in generalised assumptions and aspirational claims rather than in consistently quantified evidence. Even when sustainability is assessed, current approaches may be fundamentally incomplete. Life Cycle Assessment (LCA) is the dominant approach to environmental sustainability assessment in aquaculture research and industry. It provides quantified indicators of environmental impacts, some of which are understood and accepted by the general public, such as greenhouse gas emissions. Yet, by focusing primarily on environmental burdens per a functional unit, LCA overlooks the ecological processes and biophysical inputs that sustain production systems. In particular, it provides limited visibility into the quality of resource inputs, the distinction between renewable and non-renewable environmental support, and the broader ecological dependencies underlying aquaculture systems.
Emergy (with "m") synthesis offers a complementary perspective to LCA by quantifying the environmental work embodied in both natural and economic inputs, expressed in solar emjoules. This approach explicitly distinguishes between renewable environmental flows, non-renewable local resources, and purchased inputs, thereby revealing system dependency and environmental loading. Emergy synthesis has demonstrated that aquaculture systems vary significantly in their reliance on ecological versus industrial support, a dimension that is not fully captured by impact-based approaches.
Aquaculture systems operate at the interface between natural ecosystems and industrial production, resulting in a wide spectrum of system configurations and resource dependencies. For instance, systems range from extensive pond systems that rely heavily on ecosystem metabolism to intensive recirculating systems dependent on external energy and feed inputs. This variability highlights that sustainability, particularly in aquaculture but certainly not limited to it, cannot be fully understood through a single analytical lens. Despite this, LCA and emergy synthesis are still rarely considered together. As a result, critical resource dependencies, system constraints, and context-specific trade-offs remain hidden, limiting our ability to effectively improve environmental sustainability in aquaculture.
This work argues that sustainability in aquaculture has been systematically misrepresented when assessed solely through impact-based approaches. It examines what current practice overlooks, explores how a more integrative perspective could be articulated, and reflects on the implications of this shift for improving sustainability assessment and decision-making in aquaculture. Rather than proposing a formal methodological framework, we position LCA and emergy as complementary perspectives that can, and should, be applied together, offering a more comprehensive understanding of both environmental impacts and ecological support (Figure 1).
Current practice overlooks the divergence between environmental impact intensity and system dependency, which becomes evident when impact-based metrics are interpreted alongside emergy-derived indicators. Systems characterised by low impacts per functional unit may still exhibit high environmental loading and strong dependence on non-renewable or high-transformity inputs, including compounded contributions from feed production, energy use, and water sourcing. This misalignment suggests that apparent efficiency gains can mask underlying structural dependencies, limiting the ability of current assessments to identify system vulnerabilities and long-term sustainability constraints.
Figure 1. Integrating emergy and LCA to jointly capture ecological support and environmental impacts in aquaculture systems.
A more integrative perspective can be articulated by interpreting LCA and emergy synthesis results in parallel within a consistent system boundary, allowing environmental impacts and ecological inputs to be evaluated simultaneously. This dual-perspective approach enables the identification of mismatches between impact performance and ecological support, particularly in systems where key drivers such as feed and energy act as both major contributors to emissions and dominant sources of embodied environmental work. By linking these dimensions, the integration provides a more refined basis for comparing aquaculture systems, distinguishing between improvements driven by efficiency gains and those aligned with reduced dependency on non-renewable environmental support.
The integration of these methods has important implications for sustainability assessment and decision-making in aquaculture. It enables the identification of systems that may be optimised for impact reduction but remain highly dependent on externalised environmental support, as well as systems that operate with lower ecological loading despite moderate impact profiles. This distinction is critical for guiding system design, informing sustainability certification, and supporting policy decisions that prioritise long-term resilience over short-term efficiency gains. Ultimately, advancing sustainability assessment in aquaculture requires moving beyond partial metrics and adopting approaches that explicitly capture the interaction between environmental impacts and ecological foundations.