Forest Carbon

In light of the urgent need to mitigate climate change, many governments and companies are looking to the natural world for help, most notably through plans to plant forests to remove carbon from the atmosphere. However, the carbon — and social — dynamics of forests are complex.

Restoration of forest cover can curtail the climate crisis and provide many co-benefits, or waste limited resources. To use restoration of forest cover to its highest potential, global dynamic monitoring is needed that combines existing restoration projects with control plots and remote-sensing technologies.

Initiatives to protect carbon sinks are crucial to mitigate climate change and avert its worst effects. Advancing the rights of women and forest-dependent communities will strengthen these initiatives and enable them to have greater impact.

Forests play a key role in plans to mitigate climate change and reach carbon neutrality by sequestering and offsetting anthropogenic emissions. Nature Climate Change spoke to representatives from Tribal Carbon and If Not Us Then Who about the role that Indigenous peoples living in forest communities play in climate mitigation.

Across the globe, increasing tree cover is a popular solution to offset carbon emissions. Replenishing trees is only part of the answer, and scientists seek an increased role as part of a multi-layered policy approach.

The Global Stocktake of the Paris Agreement measures progress towards a net-zero emissions goal. Now, research provides a way to improve representation of land-based contributions to greenhouse gas emissions and removals to properly assess collective progress.

The current narrow focus on afforestation in climate policy runs the risk of compromising long-term carbon storage, human adaptation and efforts to preserve biodiversity. An emphasis on diverse, intact natural ecosystems — as opposed to fast-growing tree plantations — will help nations to deliver Paris Agreement goals and much more.

Plans to triple the area of plantations will not meet 1.5 °C climate goals. New natural forests can, argue Simon L. Lewis, Charlotte E. Wheeler and colleagues.

In this Perspective, private company supply-chain initiatives designed to reduce deforestation are assessed. Public–private policy mixes are advocated to increase their efficacy.

Changes in forest disturbance are likely to be greatest in coniferous forests and the boreal biome, according to a review of global climate change effects on biotic and abiotic forest disturbance agents and their interactions.

Nature-based climate solutions can help meet climate mitigation goals, but estimates of their carbon storage potential vary. This Review discusses the constraints and potential contributions of increasing carbon storage in the terrestrial biosphere, suggesting a conservative estimate of 100–200 GtCO₂ in negative emissions to 2100.

Deforestation and reforestation cause dramatic changes to tropical ecosystems, including underlying soil properties and their corresponding ecosystem services. In this Review, the impacts of this land-use change on soils and their functions are discussed.

There is a mismatch between emission estimates from global land use calculated from IAMs and countries’ greenhouse gas inventories. This study presents a method for reconciling these estimates by reallocating part of the land-use sink, facilitating progress assessment towards climate goals.

Disturbance regimes from fire, drought, harvest and insects will probably intensify in the future and under climate change. Despite partial offsets from regrowth, disturbance from fire and harvest reduces carbon uptake and storage in boreal forests, impacting the strength of this carbon sink.

Carbon loss from forests occurs through deforestation or the degradation of existing forest. The loss of forest area in the Brazilian Amazon was higher in 2019 than following drought and an El Niño event in 2015, yet degradation drove three times more biomass loss than deforestation from 2010 to 2019.

The amount of carbon stored in African ecosystems and how climate change will affect this is uncertain. Projections indicate that carbon storage will increase in East Africa, climate change will have an overall negative impact on woody biomass and that other human pressures will amplify the trend.

Forest management for climate mitigation plans requires accurate data on carbon fluxes to monitor policy impacts. Between 2001 and 2019, forests were a net sink of carbon globally, although emissions from disturbances highlight the need to reduce deforestation in tropical countries.

Avoided deforestation is an important part of many climate mitigation strategies, yet monitoring is needed for enforcement. Subscriptions to deforestation alerts lowered the probability of deforestation in Africa by 18%, generating a value of US$149–696 million based on the social cost of carbon.

Reforestation has been recently identified as a promising climate mitigation option. In Southeast Asia, 120 million ha of land are biophysically suitable for reforestation. However, financial, land-use and operational factors constrain mitigation potential to a fraction of its total possible value.

Predicting mortality in forests is challenging because its underlying causes are spatially varied and not well known. Reduced resilience detected from remotely sensed time series of vegetation dynamics can serve as an effective early warning signal to indicate the potential for forest mortality.

There is a growing need to find cost-effective options for greenhouse gas abatement. In this study, spatially disaggregated marginal abatement cost curves are developed to facilitate economic appraisal of tropical reforestation.

European forest disturbance—due to wind, bark beetles and wildfires—has increased in association with climate changes, but future disturbance-response remains highly uncertain. Now, research based on an ensemble of climate change scenarios indicates that an increase in forest disturbance is probable in the coming decades, with implications for forest carbon storage.

The timing of life-history events has a strong impact on ecosystems. Now, analysis of the phenology of temperate forests in the eastern US indicates that in the case of an earlier spring and a later autumn, carbon uptake (photosynthesis) increases considerably more than carbon release (respiration).

Indonesia accounts for a large proportion of the oil palm plantation expansion occurring globally. However, Indonesia’s mixed forests (and associated carbon stocks) complicate estimation of the contribution of oil palm agriculture to global carbon budgets. Remotely sensed land-cover classification combined with carbon flux estimates are now used to develop high-resolution estimates of carbon flux from Kalimantan plantations for the period 1990–2010.

The authors use economic input–output modelling to reveal how consumption patterns contribute to deforestation domestically and internationally across nations.

Investing in forest protection is a way to generate tradable carbon credits to support biodiversity conservation and climate change mitigation. Here the authors assess and map the global supply of tropical forest carbon credits with the goal of informing climate policy and investments.

Unlike Amazonian forests, African forests have maintained their carbon sink until recently but by 2030 the African carbon sink will have shrunk by 14 per cent and the Amazonian sink will reach almost zero.

Combining Earth observation data and dynamic global vegetation models, the authors show that anthropogenic land use and land cover change has caused a reduction in the contribution to the terrestrial carbon sink for tropical forests but an increase for boreal forests between 1992 and 2015.

An analysis of the overlap between tropical forest restoration, human populations, development and national policies for community forest ownership shows that 294.5 million people live within forest restoration opportunity land in the Global South.

Forest management may play an important role in climate change mitigation. Here, Tong et al. combine remote sensing and machine learning modelling to map forest cover dynamics in southern China during 2002–2017, showing effects on carbon sequestration that are extensive but of uncertain longevity and possible negative impact on soil water.

The universality of the trade-off between early growth and lifespan in trees and its implications are disputed. Analysing a global tree ring dataset and performing data-driven simulations, the authors demonstrate the pervasiveness of the trade-off and challenge current earth system models that predict a continuation of the carbon sink into mature forests under warming and increasing CO₂.

Forests are critical for stabilizing our climate, but costs of mitigation remain uncertain. Here the authors show the global forest sector could reduce emissions by 6.0 GtCO₂ yr⁻¹ in 2055, or roughly 10% of the mitigation needed to limit warming to 1.5 °C by mid-century, at a cost of 393 billion USD yr⁻¹, or $281/tCO₂.

Loss and fragmentation of contiguous tracts of primary forest enhances the susceptibility of tropical peatland and forest to fires triggered by frequent droughts, according to satellite-based remote sensing of Sumatra and Kalimantan from the past two decades

Forest stand-replacing disturbances significantly affect the biomass stocks in about a half of forested area globally, according to analyses of global forest loss from satellite data, together with a dynamic vegetation model.

Simulations of commonly proposed forest-management portfolios for Europe show that no single portfolio would meet all the requirements of the Paris Agreement, and climate benefits from forest management would be modest and local.