The carbon and climate impacts of forestation in Australia

Forestation is a feasible and cost-effective strategy to remove CO2 from the atmosphere and store it in natural reservoirs. However, it is highly uncertain how much carbon new forests can remove, how those changes will affect the climate at the local to global scales, and how a changing climate might affect the effectiveness of forestation. Here, we use the ACCESS-ESM1-5 earth system model to perform idealised global experiments of forestation to investigate the effects of additional forest cover on the Australian climate at a range of different global warming levels. Experiments include sensitivity tests that replace various fractions of existing croplands with up to 19.3 × 106 km2 of forests globally (0.58 × 106 km2 in Australia or ~8.5 times the area of Tasmania). We find that forestation on these lands can remove 40 to 80 teragrams (Tg) of carbon per year over 100 years for Australia alone compared to a scenario without forestation. For comparison, anthropogenic greenhouse gas emissions in Australia were 121.8 Tg C-CO2e in 2024. Depending on whether these forests are harvested for long-lived wood products, forestation could achieve a cumulative carbon sequestration of 5–14 petagrams (Pg) of carbon. A coordinated global forestation effort could cool Australia’s mean climate by up to 0.1–0.4°C with respect to the investigated global warming levels. However, ACCESS-ESM1-5 also projects some regional warming due to the associated decreased albedo of forested areas. With careful consideration of land cover changes to account for potential regional warming, forestation has considerable biophysical potential to remove CO2 and contribute to meeting net-zero targets in Australia and globally.