Diets within Environmental Limits: The Climate Impact of Current and Recommended Australian Diets

Abstract

Planetary boundaries are an important sustainability concept, defining absolute limits for resource use and emissions that need to be respected to avoid major and potentially irreversible earth system change. To remain within the safe operating space for humanity, there is a need for urgent adoption of climate-neutral diets, which make no additional contribution to warming. In the first study of its kind, a new climate metric, the Global Warming Potential Star (GWP*), was used to assess greenhouse gas (GHG) emissions associated with 9341 Australian adult diets obtained from the Australian Health Survey. Dietary climate footprints averaged 3.4 kg CO2-equivelent per person per day, with total energy intake explaining around one quarter of the variation. Energy-dense and nutrient-poor discretionary foods contributed around one third. With lower climate footprint food choices, a diet consistent with current Australian dietary guidelines had a 42% lower climate footprint. Currently, it is not possible to define a climate-neutral dietary strategy in Australia because there are very few climate-neutral foods in the Australian food system. To bring Australian diets into line with the climate stabilization goals of the Paris Agreement, the most important need is for innovation across the agricultural and food processing industries to expand the range of climate-neutral foods available.

Lifetime Climate Impacts of Diet Transitions: A Novel Climate Change Accounting Perspective

“…An important distinction should be made between this study and the recent application of GWP* to dietary emissions by Ridoutt, Baird and Hendrie [ 36 ]. The Ridoutt, Baird and Hendrie [ 36 ] study uses GWP* to provide estimates of relative dietary warming given trends in production between 1990 and 2018 (i.e., setting 1990 as the reference for temperature contribution). This approach assumes that trends between these years are ongoing, or in other words, sectors that are reducing CH 4 emissions per unit of product will continue to reduce CH 4 by this proportion.…”

“…A new metric called GWP* has been designed to address some of these issues by primarily considering the flow dynamics of CH 4 , given its relatively short lifetime in the atmosphere, in addition to stock impacts related to slow climatic response [ 32 – 34 ]. There has been a growing interest to explore climate impacts using the GWP* metric and recently, Ridoutt [ 35 ] has applied GWP* to life cycle assessments of food items and by Ridoutt, et al [ 36 ] to dietary emissions estimates.…”

An Alternative Nutrient Rich Food Index (NRF-ai) Incorporating Prevalence of Inadequate and Excessive Nutrient Intake

“…Additionally, the ecoefficiency of foods that address nutrient gaps was explored by calculating the ratio of NRF-ai score to environmental impact score following ISO 14045 [ 42 ]. In previous research, lifecycle assessment was used to quantify the climate footprints (carbon dioxide equivalents), water-scarcity footprints (litre equivalents), and cropland-scarcity footprints (m 2 year equivalents) of a large number of processed and unprocessed foods in the Australian food system [ 43 , 44 , 45 ]. These data have been used to develop an environmental impact score for each food [ 15 ].…”

Perspectives on Future Protein Production

“…Full life cycle analyses are required to take a whole supply chain perspective on the sustainability of food products and explore different aspects that contribute to overall sustainability of individual components of a diet. 6 Here, we examine how science and technology innovations address the environmental and nutrition impacts of various protein sources and identify further opportunities for traditional and emerging protein ecosystems ( Figure 1 ).…”