Thanks to Sue Gubbay for giving me the key words ‘Anti-trawling reefs’ and pointing me in the right direction.

Greenpeace hasn’t doesn’t done anything new in dropping the boulders in the Dogger Bank SAC.

If you type ‘Anti-trawling Reefs’ into your favourite search engine you will see lots of scientific reports on this and their effectiveness going back 30 years or more. It is a widely used tool for MPA management in the Mediterranean in particular.

Two papers:

https://www.tandfonline.com/doi/pdf/10.1080/11250000802365290

https://www.researchgate.net/publication/233487561_Antitrawling_Reefs_and_the_Protection_of_Posidonia_Oceanica_L_Delile_Meadows_in_the_Western_Mediterranean_Sea_Demand_and_Aims

This subject also merges smoothly with the idea for using artificial reefs in general which have a huge literature in terms of the multi-purpose benefits they provide – not least to fishing interests