The Anthropocene Epoch offers both unprecedented challenges and opportunities for humanity. Which of those prevails will depend on decisions made at all levels, from global to individual, over coming years. There have been many warnings of the risks arising from our current myopic development pathways but the prospect of serious, and even catastrophic, effects may not motivate action on the scale and pace required; indeed it can result in feelings of impotence and resignation.

The industrial revolution, the rise of nation states, and the emergence of market societies represented a turning point in the history of human civilization – a Great Transformation, as memorably characterized by economic historian Karl Polanyi (1). Indeed, there are echoes of Polanyi’s phrase in the Great Acceleration, the vast upscaling of the human enterprise that has brought us up against planetary boundaries (2). We can assert, without hyperbole, that another civilizational transformation is now needed – a transformation in how energy and materials are used, in how humans co-exist with the natural world, and in the accompanying social and economic underpinnings of modern societies (3, 4).

The story has to begin during the long (in human but not geological terms) period of the last nearly 12,000 years forming the Holocene Epoch, when humanity emerged from hunter-gatherer to agrarian communities and later into growing urban settlements founded on trade, and increasingly manufacturing. The Holocene was notable for its relative climatic stability, which allowed civilization as we know it to emerge. It was interrupted only by little ice ages – significant on human scale but minimally so on a geological scale. Much can be learned from the impacts of relatively modest fluctuations in climate on human society over this period (3). These lessons help us assess the likely effects of rapid climate and other changes on health and development in the future (see Chapter 2).

The Sustainable Development Goals (SDGs) were adopted in 2015 by all UN member states and represent an ambitious, far-reaching programme of action. If implemented, they would set nations on a course that significantly enhances the prospects for sustaining human progress with a lower level of environmental impacts than today’s development pathway. The SDGs are the latest manifestation of a process than can be traced at least as far back as the Earth Summit in Rio de Janeiro in 1992. There, over 170 countries adopted Agenda 21, a comprehensive action plan to catalyse a global partnership for sustainable development aimed at improving human lives and protecting the environment. The Earth Summit was a significant milestone; it established the fundamental principle that the attainment of healthy and productive lives in harmony with nature should be at the heart of the sustainable development agenda. It led to a number of crucial international conventions including the UN Framework Convention on Climate Change and the UN Convention on Biological Diversity. Nevertheless, subsequent progress was disappointing in several respects. The creation of a fair and just trading system which would foster the development of least developed countries proceeded slowly, with many wealthy nations maintaining subsidies favouring their own interests. Growth in development assistance proceeded at a slower rate than agreed and inequities between and within nations were pervasive, offsetting many of the potential benefits of economic growth. Environmental degradation continued apace, as we have seen, and the opportunity to capitalize on the momentum of the Earth Summit largely dissipated (1).

Providing equitable access to nutritious and affordable food for a growing world population in the face of multiple environmental changes is one of the greatest challenges facing humanity. Despite steep increases in agricultural yields beginning in the mid-twentieth century, the global food system is failing to provide nutritious food for much of the world’s population. The food system also imposes a heavy burden on Earth systems; it is a major driver of land use change, biodiversity loss, freshwater depletion, air and water pollution and climate change, as outlined in Chapters 1–3. Current food systems are also grossly inefficient, with, for example, overuse of nitrogen and phosphorus in some regions and underuse in others, together with high levels of food loss and waste, such that about 30% of food produced is never eaten (1). This chapter focuses on potential strategies to improve nutrition and health while reducing the environmental footprint of food systems, with the aim of staying within planetary boundaries.

Many of the dramatic changes across the planet during the Anthropocene Epoch cannot be reversed within our lifespans, so it becomes imperative to adapt to change as far as possible. According to the IPCC, adaptation is ‘the process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects’ (1, p. SPM 5). While this definition refers only to climate, the context in which adaptation has been most thoroughly considered, the concept of adaptation is applicable to the full range of planetary changes. As implied by the IPCC definition, an adaptation action might be taken proactively, to reduce harm in advance of an impact, or reactively, in response to a perceived or real health risk.

Environmental change will pose numerous challenges to health systems, as described in earlier chapters. They will need to become more resilient to shocks, including extreme events, and be able to detect and respond to changing patterns of disease (see Chapter 5). This chapter describes four major ways in which health professionals can catalyse rapid decarbonization of the economy and support moves to live within planetary boundaries while protecting health: reducing the burden of preventable ill-health; reducing the environmental impact of health care; contributing to slowing population growth; and providing broader societal leadership.

The Anthropocene Epoch confronts humanity with unprecedented challenges. Meeting these challenges demands fundamentally different modes of thought, institutions, technologies, policies, values, and governance systems than those that propelled the Great Acceleration. Humanity is at a crossroads. With environmental stressors intensifying, and with the world population growing, we need integrated solutions across sectors to address today’s challenges and to reduce future risks to a minimum. The scale of change required is dramatic.

Throughout human history, communities and individuals have adapted more or less successfully to changes in their local environments. The Anthropocene Epoch poses adaptation challenges that are new and different, both quantitatively and qualitatively, from those experienced during human history, because of both the scale and pace of the changes and the sheer numbers of humans who will need to adapt. At the same time, humanity has access – albeit inequitably – to the fruits of scientific and technological progress unavailable to previous generations, which facilitate at least some successful adaptation.

While climate change is a vitally important environmental change confronting humanity, the planet is changing in other unprecedented ways. Many of these changes – pollution, biodiversity loss, land use changes, and others – correspond to the planetary boundaries introduced in Chapter 1. Like climate change, these planetary changes also have implications for human health and well-being – the subject of this chapter. We turn first to pollution, a broad category that includes air and water pollution by substances including metals, pesticides, plastics, and pharmaceuticals. Next we consider land use and biodiversity loss – two closely intertwined processes. After land we turn to freshwater – exploring the many ways in which humans have altered the planet’s hydrology. Finally, we explore how these many changes interact with each other in complex ways.

Urban living is becoming increasingly predominant, with 55% of the world’s population currently living in cities and 68% projected to do so by 2050 (1). While megacities with more than 10 million inhabitants command much attention, they account for less than 10% of the world’s urban population. In contrast, nearly half of all urban residents – over 2 billion people – live in cities with populations under 500,000 (Table 9.1). It is in these smaller cities where population growth rates tend to be highest. The USA, Latin America, and Japan are very highly urbanized but both Africa as a whole and India remain well below 50% urbanized (Figure 9.1). Many low- and lower-middle-income countries in particular are projected to urbanize rapidly in coming decades, with a projected increase of 2.5 billion people in urban areas by 2050 – accounting for essentially all projected human population growth through mid-century.

Environmental changes, and the driving forces that dominate the Anthropocene outlined in Chapter 1, can have wide-ranging and pervasive effects on health through a range of direct and indirect pathways. One of the best recognized of these pathways is climate change – a relatively anodyne term that, thanks to growing awareness and alarm in recent years, is often now replaced by ‘global heating’, the ‘climate crisis’, or even the ‘climate emergency’.