In today’s interconnected world, a decision taken in one country can quickly affect another. A new dam may change water flows downstream; a power plant can affect air quality across borders; a highway can cut through ecosystems that do not follow national lines. This is where the UNECE Convention on Environmental Impact Assessment in a Transboundary Context, known as the Espoo Convention, plays a vital role. Adopted in 1991 in Espoo, Finland, and now bringing together 45 Parties, the Convention helps countries avoid harm before it happens. Its sister agreement, the Protocol on Strategic Environmental Assessment (SEA), goes one step further by ensuring that environmental and health considerations are built into plans and programs, not just individual projects. Together, they help countries make better decisions, reduce risks, and build trust.
Why this matters for people
At its core, the Espoo Convention is a “good neighbor” agreement protecting people’s health, livelihoods and the environment. Imagine a large industrial plant planned near a border. While one country gains jobs and investment, communities across the border may fear pollution, noise or contaminated rivers. Under the Espoo Convention, countries assess impacts together, share information and consult affected communities before decisions are made, helping prevent disputes, impacts on human health and environmental harm.
A motorway or railway crossing several countries can boost trade and tourism but also increase pollution, damage wildlife habitats and affect towns and villages along the route. The Convention helps countries to adjust routes, protect biodiversity corridors, reduce noise and safeguard local communities before construction begins.
These are not isolated examples. The Convention and its Protocol have been applied in more than 1,000 transboundary cases, showing how early dialogue can lead to better outcomes for both people and the environment.
Preventing conflict through cooperation
Its origins go back to early cases of cross-border pollution, such as the Trail Smelter dispute between Canada and the United States, which established a key principle of international law: countries should prevent activities within their jurisdiction from causing serious environmental harm beyond their borders.
Today, that principle is more relevant than ever. As countries invest in energy transition, large infrastructure and new technologies, the need to anticipate and manage possible cross-border impacts is growing.
By requiring countries to notify and consult each other, the Espoo Convention creates a practical framework for dialogue.
Planning ahead in a changing world
While the Convention focuses on projects, the Protocol on SEA starts earlier. It works with plans and programmes, policies and legislation – at both national and transboundary levels – that shape future decisions in areas such as energy, transport, land use and water management.
This matters as many environmental problems begin long before construction starts. Decisions about where to build infrastructure, how to design energy systems, or how land is used can shape environmental outcomes for decades.
By integrating environmental and health considerations at this early stage, the Protocol helps avoid costly mistakes and supports more sustainable development pathways.
This is particularly important today. Climate change, biodiversity loss and rapid technological change are increasing the complexity of decision-making.
From renewable energy expansion to emerging technologies, governments face choices that require careful assessment of risks and alternatives.
Part of a broader global effort
The Espoo Convention does not stand alone. It works alongside other UNECE environmental agreements, complementing the Aarhus Convention on public participation, supporting the Water Convention on shared resources, and reinforcing prevention efforts under the Industrial Accidents Convention.
Beyond the UNECE region, it also contributes to global environmental governance. Its principles support implementation of frameworks such as the Convention on Biological Diversity and the United Nations Convention on the Law of the Sea, helping ensure that environmental considerations are integrated into decisions affecting ecosystems worldwide.
A living framework for cooperation
Behind the scenes, the Convention and its Protocol are supported by a cooperative system that helps countries put these principles into practice. Regular sessions of Meetings of the Parties provide direction, while an Implementation Committee of independent experts assists countries in addressing compliance challenges in a constructive, non-adversarial way. Ongoing exchanges of experience through annual Working Group meetings, help countries learn from each other and strengthen implementation.
Looking ahead
A major milestone is approaching. An amendment adopted in 2001 will allow all United Nations member States to join the Convention, extending its reach worldwide. With only two ratifications remaining, its entry into force could coincide with the Convention’s 35th anniversary in 2026.
At the same time, the work under the Convention and its Protocol continue to evolve. Parties are exploring how environmental assessment can better support climate action, the energy transition, resilient infrastructure and how digital and artificial intelligence tools can be used responsibly in these processes.
Ultimately, the Espoo Convention and its Protocol are about more than procedures. They are about ensuring that development is fair, informed and sustainable, and that decisions taken today do not create problems for neighbors tomorrow.
When decisions made in one country affect communities and nature across the borders, cooperation is not optional. It is essential.