Biome5 Environment & Biocarbon Specialists

Thiaki Creek: Rainforest Reforestation for Carbon and Biodiversity

ARC Linkage Research and Biodiversity Fund Project

Demand for restoration of landscapes to sequester carbon and improve biodiversity outcomes has recently taken on a new urgency with the growing awareness that reducing emissions alone will not slow down the rate of CO2 entering the atmosphere and changing the world's climate. Sequestering carbon in vegetation and soils is essential to lock up some of the carbon and balance the carbon equation. Climate change is affecting all the world's biomes and biota. In the Wet Tropics, the impacts of climate change will be particularly severe. Extinctions of many endemic species are predicted - a result of the normally equable climate of the tropics being changed outside the usual range. Species currently surviving in small patches of habitat are threatened by changes of average temperature of less than one or two degrees, and reduced annual rainfall. Loss of diversity and resilience in the Great Barrier Reef will be a result of poorer water quality flowing from denuded catchments. Thiaki Creek is a highland tributary of the North Johnstone River which starts at over 1,000 metres and flows into the Great Barrier Reef of Far North Queensland.

On Thiaki Creek, a large-scale natural reforestation experiment is examining the best ways of reforesting a long-cleared grassed landscape to rainforest in the most cost effective way. The project was supported by a 5-year Linkage grant from the Australian Research Council, and by Stanwell Corporation, Terrain NRM Ltd, Greening Australia and Biome5 Pty Ltd. The Queensland Nature Assist program provided part of the funds. The Biodiversity Fund provided additional funds to maintain the reforestation efforts and the research. James Cook University, Uni of Queensland, Adelaide Uni, Charles Darwin Uni, Cambridge Uni and Lancaster Uni are all involved in the research.


While forestry practices using monoculture tree species have been well developed for most of a century in the Wet Tropics, reforestation practices using mixed native species for carbon sequestration and biodiversity benefits are relatively poorly developed and understood. Results of mixed plantings over the past two decades for ecosystem services have been variable, regularly producing less than optimal outcomes. This is due to inadequate background research on the founding conditions required, best species mixes and propagation requirements, uncertain but high establishment and maintenance costs, and poor economic returns. The lack of rigour has resulted in much wasted effort and money, and often poor returns from investment. The study is a multi-disciplinary one, addressing practical afforestation and reforestation methods, and ecological, economic and carbon sequestration aspects. The main research questions are being investigated:
  • What are the optimum methods for revegetating long-cleared rainforest areas?
  • Which methods are optimum for biodiversity habitat enhancement?
  • What are the carbon budgets and sequestration rates for relevant carbon?
  • What are the most cost-effective means of revegetation while achieving the other outcomes?
All questions are of vital contemporary significance, and have been poorly addressed anywhere in the world's tropical biomes.

Goals of Thiaki Creek ARC project include:
  • Maximizing biodiversity recovery
  • Identifying the most cost effective strategy for the greatest biodiversity payoff
  • Measuring the carbon benefits achievable
This is a large scale, long term research project starting with a 5-year research program, establishing experimental rainforest reforestation practices. Of special value, unique in the tropics, the research has started from the baseline of an introduced grassland baseline, a common starting point, and will allow for establishing research procedures based on sound ecological research. Most research on revegetation has started from when the trees are already in the ground. The nature of the soil and the other biota, soil and biomass carbon, soil nutrients and hydrology, and soil characteristics have rarely been studied prior to planting - the Thiaki Creek project is examining all these and more. The microclimates before and after planting are being studied and followed through the revegetation phases , using permanent data loggers so that we can start collecting air temp, humidity, soil moisture, soil temp and solar radiation measurements. Direct comparisons with standing old forests immediately adjacent to the experimental plots form an integral part of the research.

Key elements of the project include:
  • A landscape scale experiment in a dedicated area, held in private freehold
  • 30 ha for factorial replicated experimental design of 64 plots in 8 blocks, 10 plots examining planting method effects on growth, and 16 plots examining the effects of different grass control treatments
  • Existing grassland used for cattle grazing, providing opportunity to research reforestation from a common starting point of grassland
  • Immediately adjacent remnant rainforest as reference and study areas
  • GIS including DEM modelling
  • Economic analysis of the various treatments applied
  • Detailed analysis of the successful strategies for ARR, the benefits for biodiversity, and crucially, the carbon sequestration benefits to be derived from the several types of reforestation
Planting of 27,000 seedlings was completed in January 2011, a few days before Cyclone Yasi. A further 11,000 seedlings were planted in 2013, to experiment with other treatments. Species were selected on their attributes, and on the ability of nurseries to grow the species, after consultation with expert botanists, revegetation specialists, nursery people, and people experienced in planting practice in the Wet Tropics and elsewhere. Selected species are shown in the table below.
Treatment Rutaceae Lauraceae Moraceae Myrtaceae Proteaceae Sapindaceae
6 - species Flindersia
24-species Flindersia
a oblata
Acmena resa Lomatia

Carbon Budgets

Reliable models for the sequestration of carbon from grassland to forest need to be developed, as there are few world-wide. The models to date are limited in scope and number, resulting in significant uncertainties in calculating sequestration rates. Under the Land Use, Land-use Change and Forestry protocols and guidebooks as developed for IPCC, there are five carbon pools. These pools, which factor into carbon accounting include:
  • aboveground biomass
  • belowground biomass
  • dead wood
  • litter
  • soil organic matter
The easiest to measure and the one which has most published data is standing live timber. The other five have been less well studied, and some very poorly, such as soil carbon. The research proposed here will investigate and quantify the carbon in each of the pools, to provide a reliable measure for this region of the world.

Biodiversity and Ecological Studies

Research into reforestation across the world has focused on the growth rates, responses to different treatments and a range of other aspects, most of which has commenced at the time of planting. The Thiaki project is different, in that research commenced more than a year before planting. Some studies of invertebrates, soil and flora have commenced, and other studies are scheduled or proposed. They include:
  • Plant functional responses to soil nutrients
  • Soil carbon sequestration rates
  • Exotic grasses as barriers to recruitment
  • Above ground carbon
  • Plant diversity
  • Bee diversity
  • Dung beetle diversity and ecosystem services
  • Reptile and small to medium mammal diversity & abundance
  • Plant functional traits
  • Review of restoration literature
  • Economics
  • Ant diversity
  • Competitive effects of tree mixtures (inter- and intra-specific)
  • Diversity vs. productivity
  • Diversity vs. resilience
  • Relationship of spacing’s and species mixes to canopy closure rates and natural suppression of grasses
  • Mycorrhiza and other soil microbiota studies
  • Soil hydrology
  • Micro-climatology
Successful outcomes from this project will benefit landholders, industry and government by providing sound research on which to base reforestation projects for biodiversity and carbon sequestration.

The research outcomes will provide guidelines on best practice for landholders planning projects, remove the uncertainties and risks which can be avoided by using best practice, and provide better assessments of the costs and benefits from reforestation projects at small scales. Benefits to industry will include reduced risks associated with investment in carbon and ecosystem services offsetting projects, and increased certainty of outcomes. Government will benefit from carbon offsetting and biodiversity conservation being funded and managed by the private sector, reducing the need to provide funding for these offsets.

Project Partners

  • Biodiversity Fund
  • Australian Research Council
  • University of Queensland
  • Adelaide University
  • Charles Darwin University
  • Cambridge University
  • Lancaster University
  • James Cook University
  • Biome5 Pty Ltd
  • Terrain NRM Ltd
  • Greening Australia
  • Stanwell Corporation


Thiaki Creek Rainforest is located in the southern Atherton Tablelands of Far North Queensland, about 22 kms south of Atherton, at approximately 145o 51'E 17o 43'S, at elevations between 900 m and 1000 m ASL. It lies about 50 km inland from the coast on the Great Dividing Range, and is part of the Wet Tropics Region of north Queensland. The land is freehold, and covers around 181 ha, including about 130 ha of remnant rainforest Regional Ecosystem 7.8.4 (RE 7.8.4) and 50 ha of cleared land which is currently used for grazing beef cattle. Most of the cleared areas were cleared over 50 years ago, although some were cleared as recently as 1978-9. 
Aerial view of the area
This ecosystem type is largely cleared (as little as 10% remains) and the remnants are very fragmented and lie within intensive agricultural landscapes on freehold land in isolated patches across the Atherton Tablelands. The property is part of RE 7.8.4 Upper Barron complex notophyll vine rainforest complex, on cloudy wet basalt uplands and highlands. It is separated by a distance of 1.3 km from Mt Hypipamee National Park section of Wet Tropics World Heritage Area. Habitat on the land has very high conservation significance. It is habitat of the endangered Southern Cassowary Casuarius casuarius, and has core breeding populations of the rare Lumholtz Tree-kangaroo Dendrolagus lumholtzi, Lemuroid Ringtail-possum Hemibelideus lemuroides, Herbert River Ringtail-possum Pseudocheirulus herbertensis, Green Ringtail-Possum Pseudocheirops archeri and the Rare Grey Goshawk Accipiter novaehollandiae. All 13 bird species that are endemic to North Queensland rainforests (including the Cassowary) occur on the property. The remnant vegetation has previously been lightly logged using snigging practices, but retains a generally intact structure and is contiguous with the surrounding similar forest remnant.

Biodiversity Reforestation

The Biodiversity Fund, set up through the Carbon Farming Initiative, financed the revegetation of another 12 hectares on Thiaki Creek in 2013. Planted in March, the 11,000 trees filled in the spaces between the ARC plots, and the total area to revegetation is now around 30 hectares of plantings. Not missing an opportunity, we have planted some of the area to further experiments. These are investigating the differences between full or blanket spraying and strip spraying to enable planting the rainforest seedlings. So far, we have had around a 90% survival, which is very high considering the very dry winter we experienced in 2013. The experimental plots are spilt-plot designs, replicated 8 times across Thiaki. The 16 plots are monitored regularly.
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