Katrina Candy of the Game Conservancy Trust states the rather obvious effect of removing top predators from an ecosystem - their prey species will tend to have greater breeding success (letters, July 18). However, if the prey populations could be sustainable within a more naturally managed habitat, does this mean that "better" breeding success means anything more than creating a bigger surplus to be predated, whether that surplus be of meadow pipits, golden plover or red grouse?

The key to long-term sustainability of our biodiversity lies in positive ecological management so that all - the diversity part of biodiversity - can thrive. Most of the UK public are more interested in enjoying the sights and sounds of nature, rather than the sight or sound of shotguns blasting game birds out of the sky. The popularity of Glasgow's urban foxes on BBC Springwatch was testimony to that.

The Royal Society for the Protection of Birds does acknowledge the wider conservation benefits delivered by grouse shooting, because on the surface they seem obvious. There is, however, one fact that in my experience most RSPB members are unaware of, and that is that their royal charter prevents the society from taking an ethical stance against "legitimate field sports", or the morality of people who engage in them. Put bluntly, hunters get selfish pleasure out of killing animals in the name of sport. Youths on a council estate who killed cats or pigeons for fun would simply be defined as miscreant hooligans, yet others can get away with similar behaviour towards wild animals, and even be sanctimonious about it. The RSPB can hardly think such a thought without risking losing its "royal" patronage. However, I would say to RSPB members that this is not a resigning issue, and we should all continue to support that organisation's excellent conservation work.

Regarding moorland management, the reality is more complex than the superficial results much hailed by the Game Conservancy Trust. Most scientific research, with some notable exceptions, has focused on simple interspecific effects without examining how the entire ecosystem works in greater detail. There is a whole host of species on grouse moors affected by predator-prey interactions, and a number of these miss out when management is skewed heavily towards creating an extremely high surplus of red grouse. You'd think grouse moors consisted only of heather, maybe a bit of grass, grouse and a few breeding upland waders. But what about the multitude of plants and fungi (some rare), insects, reptiles, and other birds, including predatory species, which inhabit these wild places? Moorland management, especially in the form of heather burning, can devastate natural wildlife communities (not to mention causing carbon release). Even adhering to controlled burning, as recommended by the Muirburn Code, can lead to widespread suppression of tall mature heather, which supports its own suite of lichens, ground flora and insect communities, as well as providing safer nest sites for some of our rarer ground-nesting birds of prey.

Much of the predator-prey balance is influenced by one little furry creature - the field vole. Vole populations on moorland fluctuate over a three-year or four-year cycle which triggers changes in the balance between all predators and their prey, including red grouse. A longer-term cycle leads to vole "plagues" and conversely, vole "crashes". As the voles reach a peak within any given area, predator numbers build up to take advantage of abundant food; then, as they fall, predator numbers decline. However, it is a bit more complicated. During the transitional period after a peak, predators switch to alternative prey which for a time become more vulnerable; then as predator numbers reach a lower level, the predation pressure on the alternative prey decreases. Following that, vole numbers usually start to increase again, and so on. So most species of mammals and birds on a grouse moor are subject to varying levels of food surplus and shortage, and predation pressure. All of the species concerned have evolved to cope with this dynamic predator-prey relationship.

When guns and gunpowder were invented, man started to interfere in the natural process, in the Victorian era by ruthlessly reducing predators on heather moors - foxes, stoats, eagles and so on. To the RSPB, the modern results of killing only selected predators (ie, those which it is legal to kill) might seem attractive because predation is reduced on birds such as waders or hen harriers, but this is a false portrait of the bigger picture. I would suggest that subsequent long-term dramatic declines in grouse bags have partly been as a result of trying to squeeze too much out of the ecosystem, followed by a vicious circle of intensive burning and predator control in an attempt to restore the grouse numbers of the glory days, thereby upsetting the balance of nature and bleeding the system dry. A new, holistic approach to ecological management is required, and our magnificent moorlands and their biodiversity should be regarded as natural heritage to be enjoyed by all, not just killing grounds for the few.

Iain Gibson, 8 Kenmure View, Howwood.