They are where the highest rainfalls occur both in volume and intensity. This combination of natural instability and location makes them extremely susceptible to massive erosion during major rainfall events.
The only natural condition limiting this risk is the quality of the native vegetation that holds the surface together. For these reasons alone it is essential that the ranges are maintained in the best possible condition.
By the 1950s the destruction of the forest by deer, and the increasing areas of erosion and waves of gravels down the rivers were recognised as potential regional disasters waiting to happen. The NZ Forest Service (NZFS) employed full-time deer cullers. Re-vegetation studies, based around the Makahu Field Station in the Kawekas, were undertaken and erosion control programmes were initiated. By the 1980s all this work was beginning to have a positive effect.
The combination of the demise of the NZFS in the late 1980s and its replacement by the grossly underfunded Department of Conservation, the Catchment Boards replacement by Regional Councils, and the changing attitudes of Central Government resulted in a long-term resurgence in deer numbers.
There is now no systematic programme to control feral deer. Professional deer cullers disappeared with the Ministry of Forestry. Control is now the domain of recreational deer shooters. Surprisingly, the Department of Conservation has no effective national control programme. The Game Animal Council Act of 2013 introduced the concept of Herds of Special Interest, further reducing the desire to remove feral deer.
The organisation responsible for pest management in Hawke's Bay is the Regional Council (HBRC). Their policy is set through Pest Management Plans.
The current plan states, "Over the duration of the Plan, support sustainable control of population levels of feral cats, feral deer, feral goats, feral pigs, hedgehogs, mustelids, possums and rats at sites of ecological importance to levels appropriate for the protection of ecological values, recreational values and economic wellbeing within the Hawke's Bay region."
But the Council will only "assist willing land occupiers by undertaking or arranging suitable control programmes". So, the Council has no effective policy to eliminate feral deer.
Since its inception, HBRC has had no involvement with the management of the ranges, yet the health of these is critical to the future wellbeing of the region. This is a change from the former Catchment Board, which recognised the importance of the ranges and worked with the NZFS to reduce the erosion risk.
Currently, there is no organisation working to (or actively responsible for) the control of erosion in the ranges.
This lack of any effective control programmes has resulted in the uncontrolled population explosion of deer numbers. As a consequence, deer have been moving from the ranges down the gorges retired by farmers for biodiversity enhancement, into the hill country.
The absence of effective deer control for the past 40 years has meant a reduction in the quality of the vegetation on the mountain ranges. Consequently, the risk of catastrophic damage is increasing.
At a time of climate change when rainfall intensities are meant to increase, it is ludicrous that the administrations have allowed the potential erosion risk of the ranges to increase.
All that is needed is a cyclone hitting the ranges and waves of gravel will once again come down the rivers because the vegetative cover has been destroyed. Even with no major events since the 1980s the movement of gravels down the rivers can be seen upstream of Highway 50 where farmers are complaining of rising riverbed levels, which is leading to a situation similar to that in Canterbury before last year's storm event that caused such devastation.
This is happening at the same time as central and local government and local people are spending millions of dollars planting native vegetation. It could be said that all this is doing is providing ice cream for the deer. Deer numbers in the hill country have got to the stage where the Queen Elizabeth Trust is having to build deer-proof fences around its covenants.
The lack of action by the HBRC (and government) is resulting in a loss of biodiversity and an increasing risk of damage from cyclonic events for Hawke's Bay.
The effects of deer in the ranges are long term and insidious. It took many years to get deer numbers under control and forest regeneration to happen. It will take many years to return the forests to their former state.
Change requires a desire and commitment by governing bodies to undertake the change. It is relatively easy to control pests which are not protected by lobby groups, but it takes courage to do the same for feral deer, which have a strong lobby group defending them.
Without this courage to create long-term change, the risk of future calamitous events in our region can only increase.
Garth Eyles is a soil conservation consultant.
