Increased Terrestrial Carbon Export and CO₂ Evasion From Global Inland Waters Since the Preindustrial Era

Abstract

Global carbon dioxide (CO2) evasion from inland waters (rivers, lakes, and reservoirs) and carbon (C) export from land to oceans constitute critical terms in the global C budget. However, the magnitudes, spatiotemporal patterns, and underlying mechanisms of these fluxes are poorly constrained. Here, we used a coupled terrestrial–aquatic model to assess how multiple changes in climate, land use, atmospheric CO2 concentration, nitrogen (N) deposition, N fertilizer and manure applications have affected global CO2 evasion and riverine C export along the terrestrial‐aquatic continuum. We estimate that terrestrial C loadings, riverine C export, and CO2 evasion in the preindustrial period (1800s) were 1,820 ± 507 (mean ± standard deviation), 765 ± 132, and 841 ± 190 Tg C yr−1, respectively. During 1800–2019, multifactorial global changes caused an increase of 25% (461 Tg C yr−1) in terrestrial C loadings, reaching 2,281 Tg C yr−1 in the 2010s, with 23% (104 Tg C yr−1) of this increase exported to the ocean and 59% (273 Tg C yr−1) being emitted to the atmosphere. Our results showed that global inland water recycles and exports nearly half of the net land C sink into the atmosphere and oceans, highlighting the important role of inland waters in the global C balance, an amount that should be taken into account in future C budgets. Our analysis supports the view that a major feature of the global C cycle–the transfer from land to ocean–has undergone a dramatic change over the last two centuries as a result of human activities.

An Outsized Contribution of Rivers to Carbon Emissions From Interconnected Urban River‐Lake Networks Within Plains

“…Inland waters are widely recognized as substantial contributors to the global carbon budget, releasing approximately 2.1 Pg carbon dioxide (CO 2 ) and 0.093 Pg methane (CH 4 ) into the atmosphere annually (Bastviken et al, 2011;Lauerwald et al, 2023;Raymond et al, 2013;Yao et al, 2022). As a result, these ecosystems have attracted considerable attention in the estimates of regional and global carbon emissions (Lapierre et al, 2013;Tian et al, 2023;Yvon-Durocher et al, 2017).…”

“…Owing to the lengthy hydraulic residence time, lakes often retain abundant organic compounds for the generation of CO 2 and CH 4 (Kida et al., 2021; Mari et al., 2007; Striegl & Michmerhuizen, 1998). Hence, lakes have received considerable attention during the assessments of carbon emissions (Beaulieu et al., 2019; Holgerson & Raymond, 2016; Tian et al., 2023; Weyhenmeyer et al., 2015). However, organic compounds often possess higher biodegradability over the course of their transport in rivers before they reach downstream lakes (F. Liu & Wang, 2021; Wickland et al., 2012; Z. Xu & Xu, 2018).…”

Structure and Carbon Capture of a Temperate Mixed Forest across Altitudinal Gradients in Northern Mexico

“…Forests, in terms of the number of trees and total biomass, are declining worldwide because of deforestation and degradation; however, many uncertainties remain about the repercussions of these changes on the global C budget and on global climate [7,9,11]. An equivalent unit, CO 2 e expressed in tons, is a mechanism used in the C credit market [12].…”

“…As a result, studies of the various aspects of forest management have multiplied in the past years, in both number and in the broadening of their scope, in a quest to find better Land 2024, 13, 461 2 of 17 and more effective ways to manage and protect forest ecosystems. In many cases, a final product consists of the integration of the data into a model that has capabilities to run diverse scenarios [11,13]. On a global scale, computer models can integrate information about forests collected via forest inventories and/or satellite data [14,15].…”

Underway pCO2 Surveys Unravel CO2 Invasion of Lake Superior From Seasonal Variability

“…In contrast, many inland waters are supersaturated with CO 2 recycled from the terrestrial C sink and emitted to the atmosphere or exported to the coastal ocean (Cole et al, 1994;Raymond et al, 2013). These marine and lacustrine C cycles are linked by C imports and exports along the terrestrialaquatic continuum which form important elements of comprehensive global C budgets, especially in light of their perturbation by anthropogenic global change (Tian et al, 2023). Accurate predictions of climate change and mitigation efforts require an improved understanding of surface waters as sources and sinks of CO 2 and other greenhouse gases (Cavallaro et al, 2018).…”