The Dutch fleet of some 400 traditional flat bottomed sailing boats, is foundering and must be included in the Unesco world heritage list to ensure its survival, worried provincial authorities have warned.

The ships, which are now mainly rented out to tourists and for day trips, are in dire straits because of the coronavirus crisis and new environmental requirements, the Telegraaf reported on Wednesday.

A place on the Unesco list would protect the ships and make them more popular as a tourist attraction post Covid, Overijssel provincial representative Eddy van Hijum said.

Van Hijum and fellow representatives from Noord-Holland, Flevoland and Friesland are calling on politicians to convince Unesco of the importance of this ‘living heritage’. ‘The Netherlands is the only country in Europe which depends on commercial activities to keep its heritage ships afloat,’ Van Hijum said. ‘Other countries provide subsidies.’

The flat bottomed boats such as tjalks and botters are known as the brown fleet because of their traditionally brown sails. Most boats have been out of service since the beginning of the coronavirus crisis and according to the skippers some €15m in government support promised in August has not materialised yet.

More environmental requirements regarding cleaner motors and waste water are now threatening to sink the sector altogether, the provincial authorities fear.

The economic affairs ministry told the paper that the extra support package for the brown fleet is still being put together and that the first payments will be made around the summer. Skippers can also apply for the support available for all businesses, a spokesman told the paper.