Anthropogenic land use substantially increases riverine CO₂ emissions.

Area of Science:

• Environmental Science
• Ecology
• Biogeochemistry

Background:

• Inland waters are a critical, yet often overlooked, component of the global carbon budget through carbon dioxide (CO2) emissions.
• The influence of anthropogenic land use on riverine CO2 emissions is significant but requires more empirical investigation.
• Understanding these cause-effect relationships is vital for accurate global carbon accounting.

Purpose of the Study:

• To investigate the partial pressures of CO2 (pCO2) and degassing rates in a monsoonal river system (Yue River, China).
• To explore the correlation between land use patterns and riverine CO2 emissions.
• To identify key drivers of elevated pCO2 in river systems affected by human activities.

Main Methods:

• Field measurements of CO2 partial pressures (pCO2) in river water.
• Calculation of CO2 degassing rates based on measured pCO2 and environmental parameters.
• Statistical analysis, including stepwise multiple regression, to determine relationships between pCO2, land use, and nutrient concentrations.

Main Results:

• Nearly 90% of river samples exhibited supersaturation in CO2, with a mean pCO2 of 1474 ± 1614 µatm.
• Estimated annual CO2 emissions ranged from 557–971 mmol/m2/day, significantly exceeding longitudinal carbon exports.
• pCO2 showed a positive correlation with urban and farmland land use and negative correlation with forest cover, alongside positive relationships with total dissolved nitrogen and phosphorus.

Conclusions:

• Anthropogenic land use, particularly urban and agricultural development, is a primary driver of elevated riverine CO2 emissions.
• Nutrient and organic matter input from farmland and urban areas enhances riverine respiration, leading to increased pCO2.
• Land use management, including reforestation, can modify the carbon balance of river systems and mitigate CO2 emissions.