Forests may lose their carbon-storing ability due to global warming, study finds

Forests are considered the most effective and abundantly available carbon sinks, capable of storing and sequestering millions of tonnes of carbon dioxide from the atmosphere. However, a new study from India shows that global warming may be affecting and reducing the carbon uptake potential of forests, challenging the notion that forests can help mitigate climate change.

How global warming impacts the carbon uptake of forests

The study, conducted by researchers from the Indian Institute of Technology, Bombay, and published in Nature in December 2023, analysed satellite data of vegetation greenness and carbon dioxide concentration from 2000 to 2019, and found that even though greening in India has increased over the last two decades, carbon uptake by forests has reduced. The study also used climate models to project the future scenarios of carbon uptake by forests under different levels of warming.

The study found that global warming could have reduced the carbon uptake potential in forests by around 6% over the last two decades, and that this trend may continue in the future. The study estimated that by 2100, the carbon uptake potential of forests could decline by 14-23% under a moderate warming scenario, and by 29-44% under a high warming scenario.

The study attributed this decline to the physiological and ecological responses of trees to the rising temperatures and water stress. The study explained that as the climate gets warmer and drier, trees reduce their photosynthesis and respiration rates, and also face increased risks of mortality due to drought, fire, pests, and diseases. These factors reduce the ability of trees to absorb and store carbon dioxide from the atmosphere, and also release more carbon dioxide through decomposition.

Why the study is significant and relevant for India

The study is significant and relevant for India, as it has implications for the country’s climate mitigation and adaptation strategies, especially in the context of its net-zero emissions target by 2070. The study highlights the need for more scientific research and monitoring of the carbon cycle and the forest ecosystem in India, as well as the need for more effective and sustainable forest management and conservation practices.

The study also challenges the assumption that forests can act as reliable and stable carbon sinks in the face of global warming, and cautions against relying too much on afforestation and reforestation as climate solutions. The study suggests that while enhancing the forest and tree cover is important, it may not be sufficient to achieve the desired carbon sequestration goals, and that other measures, such as reducing fossil fuel emissions and enhancing energy efficiency, are also essential.

The study also points out the potential co-benefits and trade-offs of forest-based climate actions, such as the impacts on biodiversity, water resources, soil quality, and livelihoods. The study recommends that these aspects should be taken into account while designing and implementing forest policies and programs, and that the local and indigenous communities should be involved and empowered in the process.

What are the limitations and challenges of the study

The study, while being novel and insightful, also has some limitations and challenges, which the researchers acknowledge and address in their paper. The study relies on satellite data and climate models, which have some uncertainties and errors, and may not capture the full complexity and variability of the forest carbon cycle and the climate system. The study also does not consider the effects of other factors, such as land use change, fire, and human interventions, on the carbon uptake of forests.

The study also faces some challenges in terms of data availability and accessibility, as India does not have a robust and comprehensive greenhouse gas monitoring network, and the existing data is often scattered and inconsistent. The study calls for more investment and collaboration in developing and maintaining a national carbon observation system, which can provide accurate and timely data on the carbon fluxes and stocks of forests and other ecosystems.

The study also emphasizes the need for more interdisciplinary and transdisciplinary research on the interactions and feedbacks between forests, climate, and society, and the development of integrated assessment models that can support policy-making and planning. The study also urges for more communication and engagement with the stakeholders and the public, to raise awareness and understanding of the role and value of forests in mitigating and adapting to climate change.