A new model estimates that 215 million hectares in tropical regions – an area greater than that of all Mexico – have potential for natural forest regeneration, representing an above-ground carbon sequestration potential of 23.4 Gt C over 30 years.
The research team for this work was led by CBCS alumni Dr Brooke Williams and Dr Hawthorne Beyer, and included many other past and present CBCS members: Dr Renato Crouzeilles, Professor James Watson, Dr Anazélia Tedesco and Professor Jonathan Rhodes. The work was carried out through the Institute for Capacity Exchange in Environmental Decisions (ICEED) and has just been published in the scientific journal Nature.
New model to guide savings
The research team modelled the biophysical conditions that can support natural regeneration in tropical forests. Dr Brooke Williams, lead author from ICEED and the Queensland University of Technology, says, “We need broad- scale forest restoration to mitigate the biodiversity and climate crises –but tree-planting in degraded landscapes can be costly. By leveraging natural regeneration techniques nations can meet their restoration goals cost-effectively. Our model can guide where these savings can best be taken advantage of”.
Natural forest regeneration also results in higher biodiversity benefits than other restoration methods. Dr Renato Crouzellies from ICEED and Mombak says, “Where ecological conditions are such that forests can grow back on their own or with low-cost assistance, natural regeneration can be more effective than full tree planting in terms of biodiversity outcomes”.
The study showed that biophysical conditions can support natural regeneration in over 215 million hectares of tropical forests globally –with 98 million hectares in the Neotropics, 90 million hectares in the Indomalayan tropics, and 25.5 million hectares in the Afrotropics. According to Professor Robin Chazdon from ICEED and the University of the Sunshine Coast, “Identifying suitable biological conditions is the starting point, but soil and socioeconomic factors also determine the quality of naturally regenerating forests. By partnering with nature, we can reach the scale and benefits that are needed to replenish the value of lost forest ecosystems.”
Image credit: Dr Matthew Fagan
Maximising restoration actions
These results built on a dataset that identified historical natural regrowth patches, led by an international team of experts to categorise forest regrowth across tropical Earth. Associate Professor Matthew Fagan of the University of Maryland, Baltimore County, explains the method as follows: “In a previous study, we used satellite images to identify millions of small areas where tree cover increased over time. We then excluded the areas planted by humans with machine learning, focusing on natural regrowth. Those natural patches were the input data for this novel study, the first to predict where future forest regrowth will occur, given observed past regrowth.”
Dr Starry Sprenkle-Hyppolite, a co-author from Conservation International’s Center for Natural Climate Solutions, which helped fund the research, emphasises the importance of the model of the Potential for Natural Forest Regeneration. This model will enable targeted implementation of scalable, cost-effective restoration actions designed to maximise the potential biodiversity and climate mitigation benefits of assisted natural regeneration in forest restoration activities during the UN Decade on Ecological Restoration. “We are already using this dataset to explore and ground-truth ‘hotspots’ for natural climate solutions based on assisted natural regeneration, working with local communities and land managers who may be interested in allowing some of the forest to recover on their land through payment for ecosystem service schemes”.
Image credit: Dr Brooke Williams
A powerful solution for our times
As we are increasingly faced with the impacts of climate change, the team urges governments to recognise the importance of leveraging natural regeneration potential as a powerful nature-based solution for restoring vast areas of important ecosystems such as tropical forests that deliver multiple benefits to nature and people. To facilitate and promote the restoration of tropical forests, the authors have made the dataset publicly available and free to use through the data repository Dryad.
