Interactions between black, brown, blue and green carbon from terrestrial to marine ecosystems: A critical review

Abstract

Black and brown carbon are byproducts of the incomplete combustion of biomass or fossil fuels. These light-absorbing aerosols influence climate by altering the radiative balance through the absorption and scattering of sunlight, exacerbating global climate change. Their subsequent deposition on terrestrial and marine environments affects surface albedo, snow and ice melt, and biogeochemical processes, leading to further environmental consequences. In contrast, green and blue carbon refer to carbon stored in terrestrial vegetation and marine ecosystems, respectively. These ecosystems play a crucial role in mitigating climate change by sequestering atmospheric carbon; however, they are increasingly threatened by climatic disturbances, anthropogenic activities, and environmental degradation, which can compromise their carbon storage potential. Black and brown carbon interact with green and blue carbon pools through multiple pathways, including wildfire dynamics, atmospheric deposition, and fluvial transport. Additionally, these interactions contribute to climate-driven feedback loops that influence carbon fluxes and storage capacity. While black and brown carbon emissions pose significant threats to green and blue carbon sinks by accelerating climate change and ecosystem destabilization, recent studies estimate that a percentage of BC produced from biomass burning can be stabilized as recalcitrant carbon in soils for centuries to millennia, and BC buried in deep marine sediment may persist for over 20,000 years. This persistence underlies its potential role in long-term carbon sequestration, particularly through biochar application in soils and natural deposition in deep-ocean sediments. Understanding the complex and multifaceted interactions between black, brown, green, and blue carbon is critical for developing comprehensive climate mitigation strategies.