Deer: 50% cull 'necessary to protect countryside'
Around half of the UK's growing deer population needs to be shot each year to stop devastation of woodlands and birdlife, a group of scientists says.
A study published in the Journal of Wildlife Management says this would keep numbers stable.
The deer population is currently estimated at around 1.5 million.
The researchers from the University of East Anglia suggest harvesting the animals for meat to make a cull ethically and economically acceptable.
The Royal Society for the Prevention of Cruelty to Animals (RSPCA) commented that any cull must be carried out in a humane and controlled way and be supported by "strong science".
There are now more deer in the UK than at any time since the last Ice Age.
In the absence of natural predators deer populations are continuing to expand, threatening biodiversity and causing road traffic accidents and crop damage, say researchers.
Britain has a total of six deer species, four of which were introduced since Norman times. The most recent newcomer is the Chinese water deer, which became established in the wild in the 1920s.
Dr Paul Dolman, ecologist at the University of East Anglia and lead author, said: "We know deer are eating out the... vegetation of important woodlands, including ancient woodlands.
"Deer are implicated as the major cause of unfavourable conditions in terms of woodland structure and regeneration.
"There is evidence that deer reduce the number of woodland birds - especially some of our much loved migrant birds species like Blackcap and Nightingale, and resident species like Willow Tit. We have a problem."
Dr Dolman led a census of roe and muntjac deer populations across 234 sq km (90 sq miles) of woods and heathland in Breckland, East Anglia.
The researchers drove more than 1,140 miles at night using thermal imaging cameras to spot deer and provide an accurate estimate of their true numbers.
The results indicate that existing management strategies are failing. Although deer numbers appeared stable in the area, this was only because thousands of the animals were being pushed out into the surrounding countryside each year.
The new research suggested that only by killing 50% to 60% of deer can their numbers be kept under reasonable control.
Such a cull would be on a far greater scale than the 20% to 30% rates recommended previously.
With total deer numbers conservatively estimated at about 1.5 million, it could result in more than 750,000 animals being shot every year.
In a statement, the RSPCA said it was "opposed in principle to the killing or taking of all wild animals unless there is strong science to support it, or evidence that alternatives are not appropriate.
"Even if a cull is supported by science, it is very important that it is carried out in a humane and controlled way.
"Any decision to carry out a cull must be taken on a case by case basis based on the specific issues which impact a specific area. We don't believe this should be rolled out in a uniform way across the whole country. It is certainly not a case of one size fits all."
The Deer Initiative (DI), which is dedicated to a sustainable, managed deer population in England and Wales, has carried out research into how a cull might be carried out. They say that data on deer numbers and those culled need to be continually reviewed to assess whether culling levels need to be adjusted.
But its says that one off, heavy culls, followed by little or no culling, never achieve a sustained drop in numbers. Reduction culls need to be substantial and usually need to run over a number of years to be effective. They must then be consolidated by following with a realistic maintenance cull.
Dr Dolman said: "We are not killing something and then incinerating the carcass - what we are talking about is harvesting a wild animal to supply wild free-ranging venison for our tables - for farm shops, for gastro pubs.
"What we are advocating isn't removing deer from the countryside - what we are advocating is trying to get on top of the deer population explosion and try to control the problems that are being caused.
"And in a way, [venison] provides a sustainable food source where you know where it comes from, you know it is ethically sourced, you know it is safe to eat, and that puts food on people's tables. As much as I love deer, to be a meat eater but then to object to the culling and harvesting of deer seems to be inconsistent."
Previous culling estimates have been lower. The Deer Initiative had previously said that maintaining a static population will require a cull of at least 20% of the population for the larger species (red, fallow, sika), and a cull of around 30% of the population for roe, muntjac and Chinese water deer.
Peter Watson, director of the DI, commented: "The DI welcomes any research that gives us a better understanding of wild deer populations and their impacts.
"We were happy to support this work by UEA and will look at the evidence to see how it should affect our Best Practice Guidance. Our aim is promote a sustainable wild deer population that is in balance with the habitat. It is for local landowners to examine the evidence and decide how best to respond to the UAE report."
But he added that this was a single study on two species (out of six) that could not be extrapolated to the whole of the UK, therefore suggesting a cull of 750,000 was not valid. He also said deer had to be managed at a landscape-scale that reflected the ecology of the deer and not man made ownership boundaries.