The concept of planetary boundaries has resurfaced the discussion on carrying capacity and target setting for overall environmental impacts. Some authors see the concept as complementary to and compatible with the concept of sustainability. We argue here that the concept of planetary boundaries has a different ethical basis than the concept of sustainability, and that this is parallel to the incompatibility between Distance-To-Target and Damage approaches in life cycle impact assessment (LCIA). The main relevance of the notion of planetary boundaries is that it raises the issue of tipping points. We argue that it is possible to include the concern for a tipping point in the utilitarian damage approach, without the need to introduce targets, and we discuss this with the global warming metric as an example.
The paper distinguishes two ethical approaches to environmental decision-making. Sustainable development is presented as utilitarian: it weighs impacts and needs to identify trade-offs. Planetary boundaries, by setting limits that should not be exceeded, are presented as rule-based. The authors relate this distinction to life cycle impact assessment (LCIA): Distance-to-Target methods compare impacts with target levels, while damage methods assess the consequences of impacts to support trade-offs.
The authors argue that concern about climate tipping points can be included within a damage-based approach as a separate impact category, without setting a planetary boundary target. They discuss temperature metrics including GTP20 and GTP100, and note that the appropriate metric depends on the timing of peak temperature and the gases being assessed. Their conclusion is that tipping-point concerns can be addressed within a damage approach.
