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When we talk about high-impact travel, often we think about billionaires flying private jets, or the increasing number of private cars on our roads.

But what we don’t really consider is the impacts of cruise ships – and the detrimental impact they’re having on the ocean and climate.

Today, there’s a rising trend in cruise ship holidays, hitting a record high of 2.4million UK holidaymakers in 2024 , and the average passenger is getting younger, too.

While numbers of people heading out to sea grow, there’s still little in the media about the issues this kind of travel brings for the environment.

Here, we’ve broken down some of the key factors.

Air pollution

Did you know the carbon intensity of cruises is often higher per passenger than many forms of travel? To power a cruise ship across the ocean, it must burn tonnes of heavy fuel oil (HFO) – the dirtiest of marine fuels – with a single ship’s carbon footprint surpassing that of 12,000 cars over the same distance.

On average, that’s about 250g of CO2 per passenger kilometre travelled (much more carbon intensity than a short-haul flight).

On top of this, in 2022, it’s estimated Europe’s 214 cruise ships emitted more sulphur than one billion cars (over four times more than all European cars combined). When mixed with nitrogen dioxide, another harmful chemical released by these ships into our atmosphere, it turns to acid rain. The result? Harm to marine and fresh-water organisms, as well as soil acidification and nutrient depletion – all of which are vital to the increasingly fragile ecosystem on Earth.

While many cruise operators have begun investing in liquefied natural gas (LNG) as an alternative to traditional marine fuels (mostly diesel) – in line with international standards and regulations regulating emissions from ships – the reality is it remains a highly polluting source of fuel. In truth, it’s now being billed a greenwashing tool for ‘eco-friendly’ businesses to push sales.

But what’s so bad about it? Well, LNG is made up of methane, a greenhouse gas 80 times more potent than CO2 in the short term, and 30 times worse in the long term.  Essentially, it brings new – and potentially worse – climate problems.

Water pollution

Another major issue in cruise ship travel is water pollution. With so many people on board any one ship, they independently generate large volumes of water, including blackwater (sewage), greywater (from sinks, showers, laundry), ballast water (used to help maintain a ship’s stability) and bilge water (a mix of toxic liquids that collects at the bottom of a ship).

While regulations sometimes require on-board treatment, enforcement can be weak, and even treated water can still carry pollutants harmful to marine life.

To put it into context, the US Environmental Protection Agency has estimated that a 3,000-person cruise ship generates 176,400 gallons of sewage per week (adding up to over one billion gallons of sewage a year for the industry). Poor treatment can result in contaminated water washing up on our coastlines, impacting ecosystems to the point of creating ‘dead zones’, and causing sickness in people who swim or use the waters for leisure purposes.

But sewage isn’t the only problem; ballast water discharges can introduce invasive species into fragile ecosystems, disrupting local biodiversity and introducing diseases that can spread like wildfire, due to water being collected in one location and being emptied in another.

And bilge water isn’t any better. It collects at the lowest point of a ship’s hull and is made up of a mix of liquids, including potentially toxic substances such as lubricants, cleaning solvents, and metals (such as lead and arsenic). But dealing with this oily wastewater is expensive, leading to some ships dumping it straight into the ocean – like Carnival’s Princess Cruises, who were fined $40m in 2016 after pleading guilty to bilge dumping along the British coast. That leads to an oily slick that causes biological damage to sea birds (usually the first evidence an illegal dumping has occurred), as well as our coastlines and marine environments.

Even when caught, the likelihood of polluters being charged a large amount is often minimal, with enforcement sporadic, resulting in less impactful deterrence.

Noise pollution

Underwater noise pollution is also a major problem associated with the industry. Why? Because ocean noise is a threat to marine life, affecting marine animals in different ways – and can sometimes even be fatal.

Mostly, it can affect communication and orientation, degrading their acoustic habitat and affecting their ability to detect predators or find their mates. Paired with the fact that sound travels four times faster in water, it can also spread considerably further distances than by air – impacting more marine life over a further distance.

This is a particular concern with growing noise pollution doubling in just seven years in the Arctic, largely from commercial shipping. However, with the rise of ‘last chance’ tourism bringing ‘eco-friendly’ cruise ships deeper into these remote regions, marine mammals who use sound to navigate the dark waters face even greater risk than ever before.

Waste management

Though cruise ships represent less than 1% of the global merchant fleet, it’s estimated they are responsible for 25% of all waste generated by merchant vessels (including sewage, food waste, and toxic by-products from manufacturing).

In fact, cruise ships generate up to 1,000 tonnes of waste per week, with plastics from packaging, food containers, and single-use items making up a large portion. Inevitably, poor management can result in this waste making its way into the ocean, harming marine life and, over time, adding to the colossal amounts of microplastics already in our environment.

You can read more about the impacts of plastics on our marine environment, here.

The future of cruise ship travel

Globally, the cruise industry is growing, with 37.7million passengers estimated to have travelled in this way in 2025, while 68% of international holidaymakers were thought to be considering their first cruise.

That said, communities worldwide are actively fighting the industry in a bid to combat overtourism, air and water pollution, as well as the economic strain these issues put on residents living in these vulnerable environments.

As the industry grows and the environments on our own doorstep are increasingly threatened, now is the time to look at the issues and realities. And how we can have impact through our individual choices. There feels so much we can’t impact right now, but the daily choices we make can – and do – ripple out.

Keep following us on Facebook and Instagram to keep up with our latest articles and news – and don’t forget to share…

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