As Lynetteholm takes shape, questions remain over its environmental impact

COPENHAGEN, Denmark — Lynetteholm is a project to both expand the urban bounds of the city and protect Copenhagen from rising sea levels fueled by climate change. The construction of the artificial peninsula involves building a perimeter of stones and sand, which will then be filled with surplus soil from local infrastructure developments to support the city's expansion.  

In June 2026, the project completed a major milestone. The 7-kilometer-long stone embankment ring was officially complete when the King of Denmark, Frederik X, personally laid the last shovelful of stones in place.   

But Lynetteholm has been controversial from day one and marred with political obstacles ranging from numerous formal protests by locals, NGOs and even the Swedish government. Part of these protests include accusations of a lack of consultation, alleged harm to the Baltic Sea and its already struggling fish populations and contamination of the Øresund. 

Although Lynetteholm is realistically too far along to halt, concerns about its long-term environmental consequences remain uncertain and a point of resistance for many.  

Local waters and the Baltic Sea at risk 

One environmental concern raised by NGOs in Denmark and by the other countries around the Baltic Sea is that the artificial peninsula could alter the exchange of water and salt between the North Sea and the Baltic Sea.  

Denmark assessed the overall environmental impacts in 2020 before the construction project began and found that the estimated blockage of water flow and salt transport through Øresund would be around 0.23%. The estimate was set almost twice that level, at 0.5%, when a Dutch research and consultancy company, Deltares, reviewed the original assessment. 

Significant changes in the salinity balance in the Baltic Sea would cause stress to fauna and flora, as well as have larger effects on its ecosystem. However, the long-term effects of Lynetteholm on the region and the Baltic Sea are uncertain. 

Jacob Carstensen, a Professor of the Department of EcoScience at Aarhus University, among other Danish experts, has previously raised concerns about the environmental impact assessment of Lynetteholm that By & Havn conducted. According to Carstensen, the assessment was based on a 40-year-old study and has been misinterpreted from its original context.  

When asked how well the By & Havn’s framework capture the long-term damage to local marine ecosystems, Cartensen declined to analyze it further.

Rambøll, the company who later responded to the claim with a statement that assessment was indeed based on the study, as well as further data and analysis. In the report, the overall impacts on marine environment during the project’s construction and operational phase were estimated to be negligible, and in some respects, moderate with plans of mitigation to meet EU standards. 

Local opinion 

Those close to Lynetteholm, specifically the residents and workers of Refshaleøen, are unenthusiastic about Lynetteholm and the company behind it, By & Havn. 

Minna Emke, who works at the Copenhagen Contemporary said, “They're crazy. I think they have too much power. But that is my personal opinion." When asked why, she said they were causing ecological damage. 

By & Havn is owned by the Municipality of Copenhagen and the Danish Ministry of Transport and is responsible for other large projects such as Ørestad. On their website, By & Havn assures that Lynetteholm’s impacts on marine life are closely monitored.  

Another local, Tonny Petersen, doesn’t take a stand on environmental aspects. Petersen is more worried about how the back-and-forth traffic in Refshaleøen caused by construction work and future residents will disrupt the peaceful atmosphere on the island. 

“Trucks and cars will come and go, making it noisy here for a quiet life.” 

By & Havn didn’t answer a request for comments regarding the concerns of locals and NGOs. 

Coastal cities are expanding globally  

Expansion of coastal areas into the sea is a global trend, though socio-economic factors are still more prominent reasons for seaward expansion than climate protection, says a recent study. Coastal areas in cities such as Shanghai or Lagos are of high value as they provide trade opportunities, recreational benefits and an abundance of natural resources. Not to mention, they serve to increase the prominence of cities and countries that complete these large projects.

As such, this trend has left many coastal cities with the question of whether they can pursue their own similar projects and if they can do so in an ecologically friendly manner. 

Some experts, however, such as Søren Have, raise important questions on alternatives for Copenhagen based on an argument of population density. In a 2022 response to the Lynetteholm project for CONCITO, he states that with better land use in Zealand while building closer to transit infrastructure that the need for Lynetteholm for urban purposes is reduced or outright eliminated.

Søren explained over a phone call that, “More efficient and ecologically sound growth through inland alternatives is possible.”