Press release: 13 September 2021

Trouble for Lisbon airport plan as top legal official backs calls to abandon project

The Portuguese government is under further pressure to abandon plans to build a new airport on one of Europe’s most important wetlands after the country’s top legal official issued guidance confirming its insurmountable legal issues.

Portugal’s Public Prosecutor filed its legal Opinion following a case brought last year by lawyers from ClientEarth and Sociedade Portuguesa para o Estudo das Aves (SPEA, BirdLife Portugal), supported by seven Portuguese NGOs and backed by local and international researchers and organisations.

The Public Prosecutor’s Opinion strongly supports the environmental groups’ legal action against the Portuguese authorities’ failure to properly consider the devastating impacts of the future Montijo Airport on the Tagus Estuary – an internationally protected nature site which acts as crucial shelter and pit stop for migratory birds – before giving the project the green light.

The Public Prosecutor’s supportive intervention in the case is a first major success for the environmental groups.

ClientEarth wildlife lawyer Soledad Gallego said: “At a time when we need to be protecting and restoring our most precious habitats to help tackle both the biodiversity crisis and the climate crisis, the Portuguese authorities are pushing ahead with a project that would irreversibly compromise one of Europe’s most important wetlands – as well as unavoidably generating vast amounts of carbon emissions.

“The Public Prosecutor’s Opinion is extremely positive in our case to protect this iconic wetland.”

The Public Prosecutor drew attention to the major deficiencies, technical errors and inconsistencies in assessing the impact the airport would have on the Special Protected Area in the Tagus Estuary, as already highlighted during the environmental assessment of the project and as required under EU nature laws.

The Opinion also highlighted that the cross-border impacts the project would have on international and European migratory birds and therefore on other protected sites across Europe, were unjustifiably understated by the authorities. Downplaying the airport’s transboundary impact means the authorities avoided consulting other countries who might be affected by the future project.

Gallego added: “The Public Prosecutor stresses not only the importance of recognising the potential impact the project will have on migratory birds and on the integrity of the protected site, but also the potential knock-on effect it would have outside Portugal’s borders. The Opinion goes further still, highlighting further reasons why the airport should not be built, including the failure to assess the risk of major accidents, as required under the Seveso Directive.

“We hope that the Court will follow this Opinion, but more importantly, we hope that the Portuguese authorities will realise their legal duty to protect the Tagus Estuary. Primarily because protected migratory birds and habitats depend on this unique natural area for their survival, but also because of the key role these ecosystems play in ensuring a robust and healthy climate.”

ClientEarth and SPEA’s case is still pending before the Lisbon Administrative Court.


Notes to editors:

A summary of the Portuguese Public Prosecutor’s Opinion is available upon request. Please contact if you would like to receive it.

National environmental groups supporting SPEA and ClientEarth’s legal action are: Liga para a Protecção da Natureza (LPN), Associação Natureza Portugal (ANP), ZERO - Associação Sistema Terrestre Sustentável, Fundo para a Protecção dos Animais (FAPAS), Grupo de Estudos de Ordenamento do Território e Ambiente (GEOTA), Associação de Defesa do Património Cultural e Ambiental do Algarve (Almargem) and Associação Cristã de Estudo e Defesa do Ambiente Cruzinha (A Rocha).

The new airport would be located in the Tagus Estuary, close to Portugal’s capital. It is one of the main estuaries in Western Europe and is Portugal's most important wetland for waterbirds. The area affected by the new airport is protected as a Special Protection Area (SPA) and Site of Community Importance (SCI) under the EU’s Natura 2000 network; a Ramsar wetland; and a Portuguese Nature Reserve.

The Tagus Estuary regularly hosts up to 200,000 wintering birds and is the most important place in the country for wintering ducks, waders, and other waterbirds such as flamingos and gulls. Meanwhile, in any given migration season, the Tagus can play host to in excess of 300,000 birds, as it acts as a crucial pit stop for migratory birds on their long journey.

Protected migratory birds and habitats in the Tagus will be permanently disturbed if the airport is constructed, while the health of people and nature would be affected by higher levels of noise and pollution emitted from increased air, road and river traffic.

If Montijo Airport comes into operation, it is expected to have a capacity of 7.8 million passengers and 46,000 aircraft movements per year. In 2062, this is expected to increase to 17.4 million passengers and 85,000 movements per year.

Basis of the environmental groups’ legal action

In January 2020, the Portuguese Environment Agency approved the Environmental Impact Statement (EIS) for Montijo Airport.

In June 2020, ClientEarth and Sociedade Portuguesa para o Estudo das Aves (SPEA, BirdLife Portugal), supported by seven Portuguese NGOS, filed a court action with the Lisbon Administrative Court. The environmental groups argued that Montijo Airport’s Environmental Impact Statement (EIS), which approves the development of the project based on a series of assessments, goes against EU and national law and should be annulled.

An EIS is a document in which the government sets out its assessment of a project’s impact on the environment. EU law requires a series of assessments to be carried out to determine a project’s impact on a protected site. Only after these assessments have been conducted, and show no harm would be caused to the area, can a project go ahead.

Exceptions can only be made when there are no alternative options. In these cases, the authorities must provide a solution to compensate for the damages caused by the project.

In this case, lawyers consider that the Portuguese authorities have failed to carry out reliable assessments and have instead proposed to ‘relocate’ the birds that would be affected by restoring marginal areas of the protected area to compensate for any negative impacts from the airport.

Failure to fully assess the environmental impact of a project, and jumping to suggesting that birds can and will simply inhabit nearby sites instead, is a clear breach of EU and national laws.

About ClientEarth

ClientEarth is a non-profit organisation that uses the law to create systemic change that protects the Earth for – and with – its inhabitants. We are tackling climate change, protecting nature and stopping pollution, with partners and citizens around the globe. We hold industry and governments to account, and defend everyone’s right to a healthy world. From our offices in Europe, Asia and the USA we shape, implement and enforce the law, to build a future for our planet in which people and nature can thrive together.