Ted Lefroy, University of Tasmania; Christopher Johnson, University of Tasmania, and David Bowman, University of Tasmania
Deer were introduced into Australia in the 19th century for hunting. There are now six species roaming wild, and their numbers are increasing dramatically as their population expands and through human action. As they spread, they raise uncomfortable issues for conservation.
Fallow deer (Dama dama) were introduced to Tasmania for hunting by the newly arrived colonists in the 1830s. Now after 180 years, there is growing concern amongst land holders and conservationists that this species is on the move.
From a current population estimated at 25,000, modelling suggests deer could increase by 40% in the next decade. That would mean up to a million animals by mid century without additional management.
This has all the elements of a wicked problem, a stand-off with no right answer due to the uncertainty about the current population size, its rate of growth and the impact deer are having on farms and wilderness areas.
The result is a confusing and unproductive public debate between landholders, conservationist, hunters and government officials tasked with managing the deer population.
At the heart of this dilemma is the fact that fallow deer are protected under Tasmania’s Nature Conservation Act (2002), and can only be taken during a limited season through permits issued to landholders.
The wicked problem
Since the 1970s, Tasmania’s population of fallow deer has more than tripled to at least 20,000 and the area they occupy has increased five-fold to some 2 million hectares.
Fallow deer are a recognised invasive pest and a biosecurity risk, but in Tasmania the species is protected for recreational hunting.
Modelling using a conservative estimate of growth rate suggests that the population could increase by 40% in 10 years (2014–2023) and exceed one million by mid-century.
Livestock production is likely to suffer from competition for grazing and exposure to diseases such as Johnes which deer are known to carry on the mainland.
As deer spread, the Tasmanian Wilderness World Heritage Area is likely to experience more damage from overgrazing, browsing, trampling, ring-barking, antler-rubbing, weed dispersal, creation of trails and damage to wetlands and streams.
Meanwhile landholders are reporting larger and larger herds congregating on their properties, damaging crops and fences, and increased levels of unregulated hunting. The Tasmanian Farmers and Graziers Association is calling for commercialisation of deer harvesting in the face of increased numbers. Tasmania imports a tonne of wild shot venison from the mainland for the restaurant trade every week.
Bushwalkers are returning from the South West Wilderness World Heritage Area on the Central Plateau with photos of browse lines showing up in remote areas of high conservation value, well outside the deer’s tradition range in the agricultural areas of the east and north.
Why not allow more hunting?
Two reasons suggest this is not the solution. Hunters are concerned that uncontrolled harvesting will destroy the population and take away their hunting resource. And officials in the Department of Primary Industries, Parks, Water and Environment responsible for administering the game management regulations report that they are not getting full uptake of the 13,500 permits they are already issuing each year for hunting and crop protection.
One of the major limiting factors is the current management regime. Hunting and crop protection permits are allocated to landholders, requiring hunters to establish a relationship with a landholder to gain access to the deer.
The current permitting system does not allow landholders to respond efficiently to the problems posed by deer. An alternative would be a permit-free management regime in at least some land tenures or some parts of the State.
Two possible options are that landholders manage wild deer as they see fit on their own land (reducing them as much as possible, maintaining them as a resource, or tolerating them), or they could adhere to management targets agreed with government regulators. Targets might have goals such as not eradicating deer but holding populations at levels that do not cause significant conflict with other objectives of land management.
We just don’t know how many deer there are
The major factor limiting clarity in this debate at present is lack of information. There has never been a systematic survey of Tasmania’s fallow deer population.
Published estimates of the current population range from 20,000 to 30,000, but are probably too low. The population growth rate in Tasmania is unknown.
Elsewhere, populations of fallow deer are capable of growing at rates of around 55% per year. Without precise knowledge of the potential growth rate of the Tasmanian population we can’t be sure how long it could be before we have a million or so deer to contend with.
However, our modelling suggested that even if we assume a population growth rate at the low end of the range of estimates made elsewhere, the current rate of removal of deer by hunters will not prevent further growth. The annual increase in the population is likely to accelerate unless management keeps pace, something that is made difficult by the current system.
Growth of the deer population could be especially fast if more good deer habitat became available through processes such as increased wild fires opening up forests, without any change in the current permit system.
Agriculture and tourism are two of the biggest export earners on the island. An exploding deer population has the potential to damage both industries.
Investing in better knowledge would represent a small expense given these risks. Better data will not change everyone’s attitudes to deer or their place in Tasmania, but it would go a long way to shedding light on what is currently an unresolvable debate.
Ted Lefroy, Director, Centre for Environment, University of Tasmania; Christopher Johnson, Professor of Wildlife Conservation and ARC Australian Professorial Fellow, University of Tasmania, and David Bowman, Professor, Environmental Change Biology, University of Tasmania
This article was originally published on The Conversation. Read the original article.