Far North forest mega-mast good news and bad news for native species

A looming multi-mast in Northland’s forests could be good news for the kereru or native wood pigeon, as forest fruit increases, but it could also lead to an explosion of pests.

A looming multi-mast event in Northland’s forests could be good news for the kereru or native wood pigeon, as forest fruit increases, but it could also lead to an explosion of pests, conservationists warn.

Community conservation group Bay Bush Action warns that a rare phenomenon is underway in Northland’s native forests — a massive multi-mast that could either boost native wildlife populations of birds and bats … or cause a plague of rats.

Brad Windust, Bay Bush Action Trust founder and volunteer, said there was a double-edged sword of the mast season and this one was going to be a big event.

A mast occurs when plants, predominantly trees, flower together en masse every few years, producing large amounts of seeds. Most plants in New Zealand flower and seed each year, but these are mostly small flowering events. Some years there are larger-than-normal flower and seeding events. In New Zealand, masting refers to the intermittent heavy flowering of populations of trees and other long-living plants.

Mast events pose big challenges for conservationists working to protect our native flora and fauna because as well as increasing forest fruit for native species, they mean more breeding for pests such as rats, possums and stoats.

An impending massive multi-mast for Northland could lead to more predators such as possums and rats.

“Some of our native trees have a bumper crop of fruit every third year, others only every seven years. It’s called masting. This spring, the masting periods of these trees is coinciding to create what we call a multi-mast. Many native trees — including tawa, tōtara, kahikatea, porokaiwhiri, taraire, karaka and more — are all in heavy flower at the same time,” Windust said.

“It’s good news for hungry birds. More food will allow birds like kukupa/wood pigeons to have double, possibly triple, clutches of eggs so they keep nesting and raising young right into winter. But it’s also a worry. If we aren’t on top of the rat and possum populations, these pests will reap the benefit of the bounty of kai.

“Behind Paihia, in the Ōpua State Forest, we have just knocked down 10,000 possums and probably three times that number of rats since the start of the year. Here, all the abundance of fruit and seed will go to feeding our native birds, bats, and reptiles.’’

A massive multi-mast in Northland’s forests will lead to an abundance of food for native birds, but could also create a boom in pest numbers.

However, he said, most of the large northern forests were still getting little to no pest control, so it will be the possum and rats that take advantage of the fruit surplus. An explosion in rat numbers means a bumper amount of prey for stoat and feral cats, driving their numbers up, too.

“If you’re not on top of the pests, this is a perfect storm,” Windust said.

Rats can breed incredibly fast and, in the right conditions with food and shelter, two rats can multiply to over a thousand in a single year, and it’s the availability of food that drives population growth.

“Urgent action is essential. The next two months are critical. For every rat knocked down now we have potentially prevented that single rat multiplying into the hundreds by the end of summer.”

Windust is urging every bait station in Northland to be full and every trap set. “The regional council, iwi, hapū, local landcare groups, and the Department of Conservation need to pull out all the stops and fast-track as much pest control as possible.”