More than 50 million game birds a year are being released for shooting, putting increasing strain on native wild birds and the ecology of the UK’s countryside, landowners will be warned on Friday.

As management of driven grouse moors intensifies, the shooting industry must take responsibility for the impact their industry has on biodiversity and the natural environment, RSPB chief executive Dr Mike Clarke will say.

In a speech to the Country Land and Business Association (CLA) ahead of the so-called “Glorious Twelfth” – the annual 12 August official opening of the grouse shooting season – Clarke will highlight shooting management practices “of real concern”, and tell the industry it must take more responsibility for these issues.

“There are two key trends in particular. First, is the continuing increase in game birds released into the environment, now well over 50 million birds a year.

“It is ecologically naive (at best) to think that you can introduce this amount of biomass – of a similar magnitude to the biomass of all the wild birds in the countryside – without any impact on native species populations and food webs,” he will say.

“Secondly, there is a marked increase in the intensity of management on some driven grouse moors in the uplands, especially in England. As many of us know, our uplands are some of the most iconic landscapes, both for services they give people – such as water and as a carbon store – and for wildlife.”

Clarke highlights the extent of the practice of rotational heather burning on grouse moors, widely used to increase the number of red grouse available for recreational shooting.

He also draws attention to the plight of the hen harrier, a species now absent from vast swathes of English uplands. The disappearance of five male hen harriers in unusual circumstances earlier this year has led to investigations by several police authorities.

While the RSPB does not support current calls for a ban on driven grouse shooting, “the longer it takes any industry to address its problems, the stronger those calls will become,” Clarke will say.