Food systems interact with, and affect, the environment in a great many ways beyond their greenhouse gas emissions.  In order to feed humans, the global food system occupies over a third of the earth’s land surface; extracts large amounts of fish and animals from natural habitats; makes huge claims on natural resources; and dispurses various pollutants into the environment. An appreciation of this wide range of environmental impacts is needed to understand why food systems are central to solving many of our biggest environmental problems, and ultimately to maintaining human well-being. Also useful, is to understand that the causes and solutions to these problems are often interconnected through food systems, resulting in trade-off situations where a course of action can at the same time, make one issue better and another worse.

Today, billions are malnourished: not eating a diet containing energy and nutrients in healthy amounts. Both lack of food and excess of consumption cause huge levels of disease worldwide. To a significant extent, the food systems in which people participate determine what people can and do eat (i.e. their diets); and as a consequence, their health. Food systems are, therefore, central to solving many of the world’s biggest health challenges. But the way in which they affect health in different regions and among different groups of people is complex, and varies greatly. An understanding of these interconnections and their effects is needed, in order for food systems to be changed in ways that promote human wellbeing.

How food gets to our plates and what happens afterwards, connects many issues of concern, including health, biodiversity, climate change, livelihoods, and more. This chapter, and associated resources, provides an entry point into ‘food systems’ thinking and the multifaceted set of issues that are connected through food. It provides a foundation for the wider set of ideas and complexities that are explored in the other chapters of Foodsource.

It is an internationally agreed objective to cut human-caused greenhouse gas emissions to zero this century, to avoid the worst impacts of climate change. Given the major contribution of food system activities to total human-caused emissions, reducing these emissions is of great importance. But how and by how much can emissions be reduced, while also feeding a growing population? There are different perspectives on how food systems emissions can be reduced and it is helpful to explore these since these differences also underpin many other debates around food system sustainability. Understanding these perspectives helps to put specific proposals for reducing food system emissions into a wider food systems context.

Food systems are central to human well-being. We rely on them for nourishment, employment, livelihoods, culture and more. Reliable access to sufficient food is a foundation of human health, and of social and political stability. While the impacts of food systems on the environment are great, changes to the climate and the wider environment — to which food systems contribute — also have major implications for the functioning of food systems and all that they support. Understanding this matters, because sustainable food systems in the future must not only maintain human well-being with fewer environmental impacts, but must also be able to cope to different environmental conditions to those experienced today.

Emissions resulting from the many activities involved in food systems, account for a substantial portion of all human-caused greenhouse gas (GHG) emissions and, as such, contribute to climate change. A major challenge for the sustainability of food systems is, therefore to figure out how its contribution to GHGs can be reduced. If we are to be able to address and mitigate food systems’ contributions to climate change, it is important to understand where and how the greenhouse gas emissions arise across the whole food system. Also important, is to understand how different ways of organising parts of the food system, can result in differing levels of greenhouse gas emissions.

Eating patterns (or diets) are an important point of interconnection in food systems between human health and wider environmental impacts. Shifts in how people consume towards sustainable health eating patterns can bring multiple benefits. And when they are undertaken by whole populations, their overall effects can be considerable. Although there is much we still don’t know, the broad trends of what sustainable health eating patterns look like are known well enough to take action today. However, this presents another difficult challenge: how can eating patterns (at the individual and population scale) be shifted towards those that are healthier and more sustainable? Understanding this problem and its potential solutions provides a useful primer on the way in which consumption in food systems takes place through a combination of human choices (whether conscious or not), and is influenced by the wider contextual environment that actively constrains and influences these choices.

The environmental and nutritional attributes of different food types can vary greatly. Consequently, diets composed of different sets of food types, will differ in their environmental footprints, and in their nutritional quality; so affecting human health. When such differences are multiplied by many millions of people, the overall effect is considerable. Human diets are, therefore, an important point of interconnection in food systems via which change is driven – for better or worse – by shifts how people consume. At least in theory, diets might provide a means by which to achieve both health and environmental goals simultaneously. But the reality is not so simple. Understanding these complexities, helps provide a window on both the opportunities and difficulties of taking a food systems approach, and on the important role that diets play.

Food systems use large amounts of natural resources and have significant environmental impacts; so what can we do to make them more sustainable? This chapter provides an accessible primer on the life cycle assessment (LCA) methodology