Rising sea temperatures could be a particular problem for navies in the South Pacific. Hull corrosion and biofouling could worsen, pushing up maintenance and fuel costs, weakening ships structurally and decreasing their availability.

While such effects are increasingly documented in scientific literature, they appear to be overlooked in defence planning—particularly in the South Pacific, where they are intensifying more rapidly due to regional climate dynamics. In fact, in the Southwest Pacific, ocean temperatures reached unprecedented levels in 2024. This is making the ocean more acidic, with a 30 percent decrease in the pH level since the early 19th century.

Biofouling is likely to become increasingly problematic as marine heatwaves cause more frequent algal blooms. Growth of algae contributes directly to the process of fouling hulls, which occurs when ships are immobile. The accumulation of organisms on a hull increases its roughness and therefore its resistance to moving through the water. Engines must work harder and fuel consumption rises. Removing the organisms is costly and puts the ship temporarily out of action.

Biofouling also clogs and corrodes internal seawater pipes, which are essential for cooling and safety but difficult to maintain

There are few specific studies on the effects of biofouling and hull roughness on operational efficiency, with even fewer focused on the South Pacific. Nevertheless, US computer simulations of the hydrodynamic behaviour of a hull shape under various biofouling and hull roughness conditions showed, for example, that frictional resistance at 30 knots increased by 85.7 percent, speed penalties for given engine power ranged between 4.33 percent and 6.667 percent (depending on the fouling type), and propeller performance was reduced due to the effect of fouling on the ship’s wake.

A report by the Australian Centre of Excellence for Biosecurity Risk Analysis even reveals that biofouling on hulls reduces manoeuvrability, diminishes top speed by up to 50 percent and increases fuel costs and atmospheric emissions. Additionally, maintenance may become more frequent due to the need for cleaning and renewal of anti-fouling coatings. In the case of heavy biofouling, the internal piping network could degrade.

A separate phenomenon, acidification, accelerates the corrosion of metal hulls and other maritime structures. Corrosion is already among the leading drivers of the US Navy’s maintenance expenses.

Civilian ships are affected less than naval ships because they spend more of their time moving.

While the effect of rising sea temperatures on hulls is well documented globally, the specific situation in the South Pacific remains largely under-researched and underestimated. One complication that particularly needs investigation in the rapidly warming South Pacific: anti-fouling coatings are themselves sensitive to temperature and pH level, so scientists think the materials’ effectiveness will decrease.

Government-funded climate security research in the South Pacific often overlooks these phenomena. As a result, navies operating there can’t really know what complications in ship operation they’re heading for.