Carbon Emissions From Chinese Inland Waters: Current Progress and Future Challenges

Abstract

Inland waters are significant emitters of greenhouse gases for the atmosphere and play an important role in the global carbon cycle. With a vast land area in East Asia spanning a broad range of climatic conditions, China has a large number of natural and human‐made water bodies. These inland water systems are of global importance because of their high carbon emission fluxes. Over the past decades, China has experienced unprecedented environmental changes driven by rapid economic development, which have profoundly modified its inland water carbon biogeochemistry and associated emissions. This review focuses on carbon dioxide (CO ₂) and methane (CH ₄) emission dynamics from China's inland waters in response to global change. Major drivers of CO ₂ and CH ₄ emissions, including aquatic metabolism, hydrological and climatic factors, and prevailing human impacts, are examined. To advance our understanding of carbon emissions from China's inland waters, we further identify several critical knowledge gaps, such as inadequate research in headwater streams and the climate‐sensitive Tibetan Plateau aquatic ecosystems. Furthermore, insufficient understanding of carbon emissions from inland waters undergoing extensive human interventions (e.g., damming, flow regulation, pollution, and farming practices in aquaculture ponds) is highlighted. We suggest that future efforts should be made to better capture the spatiotemporal heterogeneity in dissolved CO ₂ and CH ₄ concentrations and fluxes across China as well as their long‐term trends. To overcome uncertainties in carbon sources and current flux estimates, future research to mechanistically understand carbon transport and transformation in Chinese inland waters and their underlying processes is particularly needed.

Plain Language Summary

Inland waters (e.g., streams, rivers, lakes, reservoirs, and ponds) are important sources of greenhouse gases (i.e., CO ₂ and CH ₄) for the atmosphere, affecting the earth's carbon balance. With a vast land area (∼9.6 million km ²) and diverse climate regions, China contains numerous natural and man‐made water bodies. Dissolved carbon dioxide (CO ₂) and methane (CH ₄) emissions from these inland water systems have been significantly disturbed by global climate change and human activities. This review focuses on the current research progress of CO ₂ and CH ₄ emissions from China's inland waters. Major factors controlling dissolved CO ₂ and CH ₄ emission dynamics are examined. Furthermore, we discuss the shortcomings of current research on inland water carbon emissions in climate‐sensitive regions and anthropogenically disturbed regions of China. There is a pressing need to strengthen the monitoring of aquatic CO ₂ and CH ₄ emissions over space and time and to gain a deeper understanding of the underlying mechanisms.

Key Points

• Chinese inland waters have significantly higher water‐to‐air carbon emission fluxes than lateral transport of carbon to the coastal ocean

• Aquatic metabolism, hydrological and climatic factors, and human disturbance are main drivers regulating the aquatic carbon emissions

• Dynamics of CO ₂ and CH ₄ evasion from inland waters in China's climate‐sensitive and anthropogenically disturbed regions are understudied