The ongoing battle with weeds in the Wet Tropics region has led to a three-year project across 40 hectares of land that has trialled different methods on the edges of world heritage rainforest.

Terrain NRM has worked with the Cassowary Coast, Douglas and Tablelands regional councils on projects that are buffering world heritage forest from fire and weeds, and restoring woodland habitat. They have also involved revegetation work.

Project coordinator Chelsy Maloney said the goal was to improve the resilience of big patches of native vegetation by managing emerging threats in smaller patches of neighbouring vegetation.

Restoring fire-damaged rainforest near Silkwood

In the Cassowary Coast region, the focus was a fire-damaged section of rainforest on a council reserve along the edges of world heritage rainforest.

“With the likelihood of more rainforest fires given our changing climate, it’s important to learn how to best restore these areas,’’ Terrain project coordinator Chelsy Maloney said.

“Cassowary Coast Regional Council worked with us on a weed management and revegetation project where we trialled low-cost assisted regeneration to support rainforest restoration. We found that by managing the high threat weeds, more space and less competition was created for natural recruitment and pioneer species. In the short term, the forest condition showed a definite improvement.”

Weeds were managed on 3.5 hectares of world heritage rainforest and a strip of revegetated land along the roadside.

Revegetating woodland understorey near Ravenshoe

In the Tablelands region, an infestation of guinea grass and lantana in council reserve land beside South Cedar Creek at Ravenshoe was the focus.

“In woodlands the canopy can often be intact while the understorey is overtaken by weeds. By managing lantana and guinea grass, we’ve started to see lots of different understory species recruiting across 10 hectares, and an increase in native species overall.

“We also trialled high-density understorey revegetation work on 1.5 hectares in an attempt to out-compete exotic pasture grasses such as guinea grass, and there have so far been really good results.”

Revegetation in the Wet Tropics needs to be scaled up quickly to absorb carbon and restore habitat for our plants and animals, particularly in refugia areas in future climate scenarios. However, money is the main barrier because cleared land can be used to generate an income from farming and also because it can be costly to establish and maintain biodiversity plantings, particularly in the Wet Tropics.

So, a project funded by Terrain’s Natural Capital Fund explored whether biodiversity plantings could earn money as carbon farms as a way to incentivise more revegetation.

The basic criteria for carbon sequestration are that projects have to:

• be planted on land that was cleared and then grazed, cropped, pastured or left fallow for at least 5 years (i.e. not recently cleared)
• establish and maintain trees that have the potential to grow to a height of at least 2 metres
• establish a crown cover of at least 20 per cent.

While biodiversity plantings meet these criteria and easily exceed the height and canopy cover requirements, the costs involved in registering a planting as a carbon farming project means that revenue needs to be fairly high to offset the costs. This would be possible if:

• the method used to measure the amount of carbon sequestered in a planting calculated high sequestration from biodiversity plantings, which therefore earned a lot of carbon credits
• the price of carbon credits was high
• the additional biodiversity values of biodiversity plantings attracted a higher price.

Through this project Terrain supported TREAT to run a pilot carbon farming project to analyse the costs and economic outcomes under different scenarios. The Freeman’s Forest project was registered in 2017 and TREAT volunteers planted 5000 native tree seedlings over 1.6 hectares.

A fire that burnt through world-heritage rainforest has made the Wet Tropics a barometer for climate change and a testing ground for rainforest recovery practices.

Rainforest fires are unusual – so the forest near Silkwood has become a learning area for botanists, researchers and natural resource management specialists who want to be prepared for a hotter, less predictable future.

Terrain NRM is working with the Cassowary Coast Regional Council on a revegetation and weed control project in council reserve bordering Japoon National Park, where the wildfire moved up a ridge and continued burning for 10 days in late 2018.

Terrain’s Tony O’Malley said some areas had been taken over by invasive weeds, which could potentially threaten rainforest recovery.

“We are funding the council to replace fire-promoting weeds with fire-retarding rainforest trees at the entrance to the park,’’ Mr O’Malley said. “The goal is to strengthen the park’s resilience to fire and weed invasions.”

The two organisations are also monitoring the rainforest’s regrowth by surveying sites for the next four years as part of the project.

Cassowary Coast Regional Council’s Damon Sydes said guinea grass, Siam weed, lantana and giant bramble had prospered in the five-hectare reserve since the fire.

“We began by selective spraying right across the reserve in early 2020 and then planting native rainforest trees, from Council and Queensland Parks and Wildlife stocks, in strips bordering Nyleta Rd,’’ he said.

“The trees are growing well and there’s a bit of a seed bank from the forest that’s still there so there has been natural regeneration too. This is an experiment to see if we can accelerate the rainforest’s self-repair.”