Earth at its Limits

How much change can the Earth’s ecosystems cope with? Despite red lines being drawn in the Planetary Boundaries concept, current research in Planetary Ethics shows that thorough discussion is needed on the ethical implications of such boundaries.

What rise in temperature can plants and living beings cope with? What levels of ocean acidification and deforestation are acceptable? In 2009, the Planetary Boundaries project investigated how much pressure the Earth’s ecosystems can tolerate before becoming unbalanced.

Led by scientist Johan Rockström, climate and environmental researchers designed a model for assessing the impact of global environmental changes. Threshold limits were defined for nine natural systems to consider developments such as climate change (measured by the CO2 concentration in the atmosphere), ozone depletion, land use change (measured by the proportion of forest area), water conditions and decline in biodiversity.

If humanity wants to continue to maintain stable ecosystems and an environment worth living in, it should not exceed these limits. “They created a kind of alarm system for the planet,” says ethicist Simon Meisch from the University of Tübingen. The concept of Planetary Boundaries has been much discussed since then. It also influenced debate on the United Nations Sustainable Development Goals. Despite this political relevance, there is hardly any literature that systematically examines the ethical implications of planetary boundaries, as Jeremy Schmidt from Queen Mary University of London reports. Schmidt and Meisch began work on the “Planetary Ethics” project to close this gap.

Dr. Simon Meisch, a political scientist and ethicist, works at the International Center for Ethics in the Sciences and Humanities (IZEW) at the University of Tübingen. Jeremy Schmidt was an associate professor of geography at Durham at the beginning of the project and now teaches environmental geography at Queen Mary University of London. As part of the Planetary Ethics project, Schmidt and Meisch held discussions with researchers from the humanities, natural and social sciences, political consultants and artists worldwide.

Who defines the boundaries?

As Earth gets ever closer to exceeding the Planetary Boundaries – six have already been crossed – we need answers rather urgently. What effort does humanity have to make to meet the targets? What happens when boundaries are crossed? From an ethical perspective, researchers believe that we need to investigate additional questions: Can such boundaries be meaningfully defined, and by whom? Do boundaries apply globally or do they need regional variations? Who is ultimately responsible for political action?

The concept looks like a scientific model, explains Meisch. “However, it is based on normative assumptions that are not transparent.” For example, it has long been contentious that the planetary boundaries were defined by a small group of researchers from Western industrialized countries. Does this mean that Europe and the USA are imposing their views on the rest of the world?

Schmidt suggests that the threat of exceeding boundaries may be perceived differently. Planetary boundaries are designed to be generally applicable and do not take any individual interests into account by nature. For instance, the loss of biological diversity or changes in land use always concern specific areas that people inhabit and cultivate, as Simon Meisch explains.

Agriculture is often seen as a source of problems. But it also serves as a livelihood for significant segments of the human population. “Families who have cultivated their land for generations can be intimately connected to it.” Similarly, policies aimed at preventing the crossing of a Planetary Boundary could interfere with Indigenous ways of life. “Indigenous peoples are particularly important for the protection of biodiversity as many biodiverse reserves can be found on their territories. Western concepts of biodiversity, strongly influenced by the natural sciences, can be at odds with ideas about how Indigenous peoples understand and live their relationships with non-humans.”

How does this influence our decisions?

In the area of biodiversity, seeking a fair balance seems almost impossible: Which species has the privilege of a habitat? Should newly introduced invasive species be slowed down? Schmidt refers to the site of the 2000 Olympic Games in Sydney, which was built on an industrial wasteland. Due to high levels of pollutants, many animals cannot live there – except for a frog species that has found its niche. Should this species be given priority or the land be renatured?

Rarely is there a single strategy to avoid crossing boundaries. The model does not name any polluters and fails to consider all aspects in detail. The “Novel Entities” section covers new substances introduced into nature by humankind that are very different. “This can include nuclear waste, microplastics or drug residues,” says Meisch. “Each of these problems requires a different action plan.” Even in addressing the depletion of the ozone layer, the only field that has so far been considered a success, there is still underlying criticism. Although substances such as CFCs were contained in an international effort, other harmful substances are not even mentioned.

Earth system ethics

There was a great need for discussion on the topic among all researchers, says Meisch. “They are quite alarmed about ecological developments.” Evidently, there is a need for a nuanced debate that is more detailed and focused. Listening to others and accepting that definitions of quality of life can vary widely is a start. “In a world that is becoming increasingly networked, demands for justice should be phrased and justified in such a way that they consider everyone’s needs.”

Academics, artists and practitioners discussed each of the nine planetary boundaries in a series of video conferences. The debates will be documented in a volume published by Cambridge University Press and continued in a podcast series. Meisch and Schmidt hope these educational materials for schools and universities will encourage to deal with the questions raised in the debate. From 2025, it will be accessible free of charge to as many people as possible. The project outcome is intended to establish a foundation for “Earth system ethics”. It raises ethical questions that arise in processes on a planetary dimension that affect the entire Earth system. The project team already consider it a success that through the discussions they were able to provide a space for contributing to the debate. “We are encouraging people to think and reflect – this broadens perspectives and may in turn lead to greater involvement.”

Pushing our planet to its limits

The Planetary Boundaries (PB) concept was designed by 28 Earth system and environmental researchers, led by Swedish scientist and current PIK Director, Johan Rockström. The team defined nine environmental boundaries that represent a safe space for our actions on the planet. Exceeding one or more boundaries can be harmful or even catastrophic by causing abrupt environmental changes in Earth systems.

In 2023, the researchers quantified the status of all nine processes and systems. The sobering result: Six of the nine boundaries have already been crossed.

Text: Stephan Köhnlein