Forest & Bird has released drone footage of once-in-a-decade heavy flowering of northern rata, Northland conservation advocate Dean Baigent-Mercer saying the species had "dodged a bullet."

They weren't out of the woods yet though.

"Ancient rata giants used to tower alongside rimu over much of Aotearoa. Together they dominated the rainforest skyline," Mr Baigent-Mercer said.

"The ancient northern rata standing today began growing before possums were introduced, and even without the new threat of myrtle rust, they are now reliant on us for their survival because they are such a favourite food of possums."

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Drone footage taken over an area of Otangaroa Forest that had benefited from multi-species pest control that targeted possums, rats, stoats, weasels and feral cats for seven years showed rata in full bloom, contrasting with the greyness of possums' damage on other northern rata and the trees surrounding them.

"They have dodged a bullet, and are clearly coming back to life," he said, "but in northern native forests, like Russell State Forest, without comprehensive pest control they are dying.

"Russell State Forest is in active collapse without pest control. The northern rata there are probably over 500 years old, and are dying on our watch. Russell State Forest urgently needs comprehensive pest control that will turn around the collapse."

Scientific research had shown possum-wrecked native rainforest canopies took 20 years to recover, once possum numbers were reduced to as close to zero as possible.

"Native rainforest canopies should be lush greens, but the greyness you see in the drone footage is from decades of possum attack," he added.

"Pest control targeting all the introduced animals builds the natural resilience of the forest for the challenges ahead."

Meanwhile rata and pohutukawa species now faced an even more uncertain future, as myrtle rust was being found to be increasingly widespread areas.

"It's important to make the most of this year's very heavy flowering of northern rata, because the trees will soon be producing an abundance of seed," Mr Baigent-Mercer said.

"Forest & Bird has made a short video showing how to collect seed and grow northern rata. If the seed doesn't find a place to germinate within weeks, the seed is dead."

Forest & Bird encourages members of the public who find myrtle rust not to touch it but to report it to the MPI (www.mpi.govt.nz/protection-and-response/responding/alerts/myrtle-rust).