Sunday, August 14, 2022

Possums’ genetics may seal fate

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A better understanding of the genetic technology that could eradicate possums from New Zealand’s landscape does not necessarily mean the pest will undergo gene-editing to get rid of it.

Predator Free 2050 science director Professor Dan Tompkins says New Zealand has a very good chance of eradicating possums by 2050.

A better understanding of the genetic technology that could eradicate possums from New Zealand’s landscape does not necessarily mean the pest will undergo gene-editing to get rid of it. As Richard Rennie discovered, greater genetic understanding may, however, mean researchers have more options for dealing with the pest.

Latest data indicates the Government is spending a million dollars a week controlling possums, on top of a similar amount by regional councils, in addition to the $40 million the pest is costing farmers a year, largely in Tb control and management.

A research partnership between Predator Free 2050 (PF2050) and the University of Otago has the university’s genetic research team receiving an injection of $300,000 to boost research into genetic control solutions. 

Ultimately PF2050’s aim is to eliminate all possums, but the genetic focus does not necessarily involve controversial gene editing tools.

Predator Free 2050 science director Professor Dan Tompkins acknowledges the subject of gene editing in any shape or sense is a politically a sensitive one.

More than three years ago the Royal Society ran a roadshow highlighting the potential benefits gene editing could offer, including in areas of pest control and enhanced crop production. However, debate has moved little since then.

“But the actual state of play for gene editing technology is well behind what many try to sell it as. It is something that gets kicked around politically, both nationally and internationally.

“People do tend to fixate on a few uses, but it is a tool to help give a richer understanding on how organisms work. It could be we could design a new toxin if we better understand the possum’s genetic make-up, for example.”

While not tasked with unravelling the possum genome, something another research team is already committed to, NZ researchers have already led the way in unravelling the stoat and the Rattus rattus or ship rat genome, in a country where both have far greater impact than in their native habitats.

Under PF2050 and a concerted Tb Free policy, NZ has been faring relatively well in possum elimination over the past decade. 

“The early reports on our PF2050 landscape projects are positive. Taranaki, for example, is reporting large chunks of land now where possums are just not seen, in some cases for more than six months.”

But complete eradication gets tougher as the country gets tougher. Fore example, remote West Coast landscapes are prime areas that will demand more tools to achieve the job.

“The tools and approaches for possum eradication are continuing to improve. But the scale of the PF2050 mission means new solutions and approaches are needed. If we go into an area and leave one pregnant female behind, it’s a failure.”

Putting staff and traps into remote areas is a common strategy but is proving increasingly expensive per trap as those numbers decline.

Possums by their nature lend themselves well to complete eradication, eventually.

“They are relatively long-lived, they have a long home range meaning you can put in relatively dispersed traps. They are also relatively slow breeders – if you miss some, it takes them a while to build back up to critical numbers, you have the time to act.”

Research team leader Dr Tim Hore of University of Otago said while gene editing is going to be a valuable and flexible addition to the possum research toolkit, the techniques to edit the genes have not yet been developed.

He said technologies could be developed that reduce possum fitness, inducing gradual population decline and local eradication.

Tomkins said any researcher will be very wary of gene editing technology that could transfer to the native Australian possum population.

“That would be a breach of the Cartagena Protocol, which aims to ensure the safe handling and use of modified organisms that have an effect upon biological diversity.” 

If it impacted upon a country’s native population, NZ would also be liable under the UN convention on biological weapons.

He suspects it is more likely that in the coming five to 10 years NZ will develop better toxins that only affect possums, thanks in part to the knowledge this project gleans on their makeup.

“Another option is to develop some sort of fertility control that they eat as they do a toxin, which cuts back populations.”

Any gene editing technology that passed on heritable traits to reduce populations could at best be 10-20 years away and very much subject to social and policy conditions before it could be used.

“And a lot of it is theoretical and may not be possible.”

Meantime Professor Tomkins and his colleagues at PF2050 are confident there is still a very high likelihood possums will be eliminated from NZ.

“The big thing for me is that this project has maintained its life beyond the political cycle and there is significant ongoing public support for it to continue.” 

More recent work on carbon sequestration has also added to the incentive of 100% removal of a major Tb vector and vegetative destroyer.

Satellite sensing of offshore pest-free islands including Little Barrier and Motiti has shown removing pests has led to measurable carbon lifts on half the islands. 

The Climate Change Commission has also recommended ongoing pest management to protect the carbon sequestered by native forests.

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