Dazzling, marvellous, sublime – open a thesaurus and you'll find any number of synonyms for "glorious". Cold-blooded, inhumane, and shameful are not among them.

But the latter go hand in bloody hand with the "Glorious Twelfth", the annual red grouse killing spree whose dark curtain is raised today on the upland moors. Before it concludes in December, hundreds of thousands of the shy, iconic birds will be gunned down in an arrogant display of savagery that its moneyed participants would have us believe is "sport". It's worth noting here that "sport" implies a fair contest between evenly matched opponents – and blasting birds, who wish only to live undisturbed, out of the sky is certainly not that. Indeed, if there were a group of people preparing to shoot dogs and cats for fun, we'd be screaming bloody murder – and honestly, what's the difference? Birds have the exact same capacity to experience pain and suffering as dogs and cats do.

The killers pay the owners of the estates where the massacres are staged around £180 for each pair of birds they slaughter; it can cost £50,000 for cliques of eight to indulge their bloodlust for just two days. Some high-end London restaurants then hustle to serve the first grouse killed – and before the first day of killing ends, they'll be decapitated, disembowelled, and on the menu for nearly £90 a plate.

No training or proof of experience is required to go grouse shooting, which means many birds will be left to die lingering, painful deaths after being shot by inexperienced shooters. Two years ago, about 700,000 red grouse were gunned down, a shameful toll of lives lost and families destroyed. And this number doesn't even take into account the environmental price being paid so that a few callous elitists can fool themselves into believing they're brave hunters.

Grouse eat heather shoots, so in order to stimulate their growth (and thereby attract the birds), moor managers systematically burn the peat-rich moors, which encourages fresh shoots. But in burning off vegetation, they expose the peat, which is rich in carbon. These carbon stores then decompose and release carbon dioxide.

The Committee on Climate Change has estimated 350,000 tonnes of carbon dioxide is emitted each year from the upland peat, and the majority of that amount – 260,000 tonnes – is caused by burning on the grouse moors. And it's becoming worse, just as the need to halt climate change is more urgent than ever: A study released last year by the Royal Society for the Protection of Birds (RSPB) found peat burning had jumped more than 100 per cent from 2001 to 2011.

In addition, while lead ammunition has been banned elsewhere because it is toxic to wildlife and humans, it is still in favour on the moors. In good condition, Scotland's spongy deep peat land habitats also provide clean drinking water and help hold back water that would otherwise flood low-lying areas. But large quantities of the poisonous lead shot is discharged on the ground from shotguns, further harming both the environment and human health. These environmental concerns have largely been overlooked so shooters and estate managers can continue in their bloodthirsty ways. Other animals also pay the price for these killers' folly. Hen harriers, golden eagles, and peregrine falcons – protected birds of prey and the grouse's natural predators – are shot, poisoned, and trapped so that hunters will have more grouse to kill. The situation has become so bad in recent years, that the Royal Society for the Protection of Birds wrote to all UK political parties asking them to introduce a licensing system for grouse moors, so licences for grouse shooting could be withdrawn if there was evidence of the illegal killing of wild birds – particularly those species who are being driven to extinction because of this. And it's not just birds of prey, other natural predators, including foxes, crows, and stoats, are also killed by the thousands every year.

Let's hope that one day soon, this pompous and arrogant tradition will be banned alongside other violent pastimes, such as hare coursing, and that the 12th of August will come to represent progress and morality, rather than blood and barbarism. Until then, the "Inglorious Twelfth" will remain an ugly blemish on Scotland.

Yvonne Taylor is Senior Manager of Corporate Projects at Peta UK.