Environmental Ranking 2025: How harmful are cruise ships?

For many people, a cruise is the fulfillment of a vacation dream: multiple destinations in a short time, luxurious ships, and the feeling of exploring the world's oceans. But behind the romantic facade lies a dark side. Cruise ships are among the most climate-damaging modes of transport; their engines emit enormous amounts of greenhouse gases, particulate matter, and nitrogen oxides. Furthermore, waste and wastewater exacerbate the strain on marine ecosystems.

At the same time, the industry is growing inexorably. Around 35 million travelers worldwide boarded cruise ships in 2024, and industry associations expect this to rise to over 40 million annually by 2040. This boom not only presents ports with logistical challenges but also forces shipping companies to find answers to the pressing question: How can cruises be made more climate-friendly without jeopardizing their economic success?

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To show which shipping companies are already taking action and those who are still struggling, the German Nature and Biodiversity Conservation Union (NABU) publishes a cruise ranking every year. The results for 2025 are also mixed: progress has been made, but the truly significant levers remain unused.

The Norwegian shipping companies Havila and Hurtigruten lead this year's ranking, each scoring 7.5 out of a possible 15 points. The French luxury cruise line Ponant follows in third place (seven points). Among the German companies, Tui Cruises , with its Mein Schiff brand, performed best, scoring six points and taking fourth place, followed by Aida Cruises with 5.5 points in fifth place.

At the bottom of the list is an international industry heavyweight, Royal Caribbean (3.5 points). The last two places are occupied by Phoenix Reisen and Viking Ocean Cruises, both of which received zero points because, as in previous years, they didn't even respond to NABU's questions.

NABU notes positively that all assessed shipping companies are now committed to the goal of "net zero by 2050." This means that by 2050, the shipping companies aim to capture as many greenhouse gases as they emit, thus reducing their emissions to zero. In addition, many shipping companies have made their ships more energy-efficient, for example, through optimized routes, reduced speed, or technical modifications such as air bubble carpets on the hull, which reduce friction and thus reduce fuel consumption.

A growing portion of fleets can also use shore power in port. Pioneers include Havila, Hurtigruten, and Mein Schiff, while other operators are still lagging behind. In cities like Hamburg, Kiel, and Rostock, connections for the cruise giants are already available throughout the port, and ships docking there can cover their entire energy needs with shore power while at the dock. However, in practice, many ships continue to run their own diesel generators despite this option.

The cruise industry's real weakness, however, remains propulsion at sea. The majority of shipping companies continue to rely on cheap heavy fuel oil, even though switching to less environmentally harmful marine diesel is technically straightforward, explains the German Nature Conservation Union (NABU). Instead, on many ships, heavy fuel oil is often combined with exhaust gas scrubbers that filter the sulfur content from the smokestacks but discharge the residues into the sea. Toxic heavy metals and other toxic substances thus enter the water and pollute ecosystems.

Truly sustainable solutions such as synthetic e-fuels or green methanol have so far been largely ignored. Instead, the focus is primarily on fossil LNG (liquefied natural gas). However, the gas neither saves greenhouse gases in the short nor the long term and is more of a fake solution for shipping companies, according to the NABU. Meanwhile, hardly anyone is investing in truly green fuels, and even the propulsion systems of the current new cruise ships aren't showing any glimmer of hope.

There are, however, some small advances in the industry, for example, in the use of batteries and fuel cells, which can at least save fuel in ports or during maneuvering. The use of sails or rotors for wind assistance is also being tested by a few pioneers such as Ponant or Hurtigruten . Overall, however, these technologies remain the exception, and comprehensive decarbonization strategies are not in sight.

The conclusion of the NABU cruise ranking is accordingly sobering. While individual cruise lines are certainly taking steps to operate more sustainably and reduce their emissions, the industry as a whole remains far behind. Despite small efficiency gains, the industry continues to grow, and with it, the overall emissions of cruise tourism. Therefore, the most sustainable cruise is still the one that doesn't take place at all, according to NABU's sobering summary of the current situation in the cruise industry.

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