States’ obligation to conduct environmental impact assessment: Lessons from international advisory opinions on climate change, and legislation and regulation around the world

Environmental impact assessment (EIA) is a formal evaluation process to understand the environmental impact of a proposed public or private activity, such as the building of new transport infrastructure, housing development or industrial facilities. Embedded in more than 180 domestic legal regimes, EIA is a nearly ubiquitous tool of environmental governance. However, many domestic legal regimes governing EIA processes are silent on the assessment of climate-related impacts. This lack of clear guidance creates uncertainty and may lead to contestation in courts.

This policy insight, developed in collaboration with the Commission of Small Island States on Climate Change and International Law (COSIS), analyses what the international legal obligation to conduct EIAs entails in the context of climate change. It presents the findings of the recent advisory opinions from the International Tribunal for the Law of the Sea (ITLOS) and the International Court of Justice (ICJ). These opinions reaffirm that EIAs form a core element of states’ due diligence obligations to prevent significant environmental harm, including harm to the climate system and the marine environment.

Drawing on existing state practice, the authors identify legislative and regulatory options for states to strengthen domestic EIA frameworks and better align them with requirements under international law.

Key points for decision-makers:

• Legislators should adopt or amend EIA legislation and regulations to explicitly require the assessment of climate impacts, particularly from high-emitting projects.
• Regulators and relevant public authorities should develop detailed rules, methodologies and technical guidance to integrate climate-related considerations throughout the EIA process.
• Governments should provide sufficient institutional capacity, technical expertise and financial resources to enable the effective implementation and enforcement of EIA requirements.
• Legislators and regulators should ensure that climate adaptation and resilience measures are adequately considered and addressed in EIAs.

DOI: 10.21953/researchonline.lse.ac.uk.00141852