Wilding conifers and Bovine Tb – spend now to save later
Date: 18th December 2025
History shows that large scale, long term national biosecurity programmes need to be adequately and consistently resourced over the full extent of their lives. Failure to complete these programmes in the most cost effective and timely way can result in large, long term economic and environmental costs to New Zealand. Richard Bowman, past WPN chair who experienced the Tb crisis firsthand has written the following op-ed.
Currently we are facing a major national biosecurity threat from wilding conifers. These are self-sown introduced pine species which have spread out from shelterbelts, wood lots, soil conservation plantings and commercial forests. They now affect over 2 million hectares of the country. Potentially they could affect up to 6 million hectares or 25% of our land area. Their impacts are greatest in the hill and high country of the South Island and central North Island. Here they reduce farm production, displace native biodiversity, reduce water yield (at the expense of irrigation and hydro generation) and increase wildfire risk. It has been shown by a cost benefit analysis commissioned by MPI in 2022 that these impacts could cost New Zealand $3.8 billion over the next 50 years.
Image sourced from NZ Geographic.
Since 2016 over $150 million has been spent nationally on wilding conifer control. This has achieved initial containment of spread in most areas. However, another decade of maintenance is required to remove seed sources and exhaust seed banks in the soil. Currently the national programme is funded at a little over $10 million per annum. This is inadequate, and the gains made in many areas are now being lost which is effectively writing off the initial investments made.
Realistically the national programme needs at least an additional $15million a year just to hold the progress made to date. To achieve effective long-term control of wilding conifers nationally could require up to $50M a year for the next 10 years. At present repeated requests for additional funding required to complete the national wilding conifer control programme have not been met either by the Government or by all of those who benefit from the programme or those who contribute to the need for it. Failure to find this funding will result in significant long-term impacts on New Zealand’s economy and environment as well as on a range of important social and cultural values.
There are important lessons to be learned about this lack of funding problem from the history of other national biosecurity response programmes. One especially relevant example is the national Bovine Tb Programme. This is regarded as a major success story in animal disease management both here and internationally. Since 1997 over $1.5 billion has been invested in the control of the disease which has reduced the number of infected cattle and deer herds from a peak of 1700 in 1994 down to 15 in 2025. This has greatly reduced the risk of serious potential economic losses to agricultural production and trade. In addition, reducing the populations of possums, which act as carriers of the disease that infect livestock, has provided major benefits for native biodiversity across many parts of New Zealand.
The national Bovine Tb Programme has been a long running and hard-fought battle against a range of biological, ecological as well as political and social factors. Its history can be seen in the graph below showing the relationship between the numbers of infected cattle and deer herds and annual programme expenditure.
Graph showing numbers of Tb infected herds vs annual expenditure
Source: TB Plan Governance Group, Andrew Bevin | Newsroom Pro September 2025
One of the most important messages from this graph is that it shows when a programme is not funded adequately funded or funding is stopped then the problem can expand at an exponential rate. This greatly increases the costs of solving the problem. Prior to 1977 there was a sudden surge in Tb infected farmed cattle. This was due to wild possums which had become infected with the disease. It meant that when herds were tested and infected animals culled the clean herds soon became infected again by Tb possums living on an around farms. To counter this Government started investing a few millions of dollars a year on possum control in the affected areas. Correspondingly herd infection rates fell rapidly. Based on this initial success, it was decided to stop possum control funding in 1978. Unfortunately, after this the number of infected herds rose dramatically to a reach a peak of 1700 by 1994. Funding of disease and possum control finally started again after a 10-year gap around 1988. Following this a long period of steadily increasing expenditure was required until finally the number of infected herds started to decrease significantly around 1999. The point to be made here is that if the modest programme funding had continued beyond 1978 then this may have avoided the massive increase in infected herds in the mid-1990s. It could have potentially saved hundreds of millions of dollars of taxpayer and industry money.
It would be most unfortunate to see history repeated in the case of the national wilding conifer control programme. When you are dealing with national biosecurity threats that can increase at exponential rates the sooner you invest in an effective response the greater the return on your investment. Any delays will vastly increase the costs of getting on top of the problem. The case for early and consistent year on year levels of funding of wilding conifer control is powerfully supported by the MPI cost benefit analysis which gives a benefit to cost ratio of 32:1. This means that a dollar spent today will prevent $32 of cost over a 50 year period. It should be noted that this is several times greater that the benefit cost ratios calculated for the national Bovine Tb programme.
Richard Bowman – 22 November 2025
Posted in: News