Baseline development
The report analyses global development trajectories using the planetary boundaries framework and the Integrated Model to Assess the Global Environment (IMAGE) up to 2050. Baseline scenarios indicate continued degradation of Earth’s environmental systems, with key planetary boundaries—climate change, biogeochemical flows, land system changes, atmospheric aerosol loading, and biodiversity—already transgressed or nearing critical limits by 2030 and 2050. Ozone depletion is the only boundary improving, reflecting successful global regulatory measures. Business-as-usual (BAU) conditions show intensified pressures, moving climate and nutrient flows into high-risk zones, while freshwater use and ocean acidification approach critical thresholds.
Living within planetary boundaries
To counter worsening environmental impacts under BAU, the report examines the potential effects of ambitious global policy interventions. Implementing the Paris climate agreement (limiting warming to 1.5°C) considerably reduces greenhouse gas (GHG) emissions. However, radiative forcing remains above safe limits in 2050 due to inertia in natural systems and societal change. Climate policy alone is insufficient, though it has synergies with nitrogen management, air pollution reduction, and modest improvements in land use through reforestation.
Further sustainability interventions modelled include a shift towards the EAT–Lancet planetary health diet, halving food loss, enhancing water-use efficiency by about 20% in non-agricultural sectors and 30% in irrigation, and increasing nitrogen-use efficiency by 70–80%. These combined measures substantially reduce environmental pressures, bringing indicators like aerosol loading and land system changes back to or below 2015 levels. Despite these improvements, several planetary boundaries remain transgressed due to existing environmental and societal inertia. The study highlights that such policies, while technically feasible, face considerable social and institutional barriers to implementation and thus require further feasibility studies.
Living well in a dynamic safe operating space
The report underscores that current trajectories pose severe risks to Earth’s systems. Effective management of planetary boundaries requires integrated policies that simultaneously address climate change, biodiversity loss, nutrient pollution, and water use. The authors emphasise the importance of coupling dynamic scenario modelling with planetary boundary indicators to guide policy-making.
To effectively achieve sustainable development, immediate and transformative actions are necessary. These include robust climate action aligned with international agreements, widespread adoption of sustainable dietary practices, significant reductions in food loss, and technological improvements in resource efficiency. The report advocates further development of standardised planetary boundary indicators to enhance policy applicability and clarity.
Furthermore, addressing planetary boundaries must consider equity and justice in implementing these substantial societal transformations, as public support for ambitious measures is strongly influenced by their perceived fairness.
The report notes limitations due to reliance on a single modelling approach and suggests future multi-model comparative studies to enhance robustness. It concludes that without proactive and transformative actions, key Earth systems risk irreversible damage. The integration of ambitious policies presents a clear pathway toward reducing risks and steering global development toward sustainability. However, even these ambitious scenarios highlight the significant inertia in reversing current trends, underscoring urgency and universality in implementing comprehensive global sustainability measures.
