Tropical rivers emit far more climate gases than lakes, new study finds
Flowing waters in tropical and subtropical regions release roughly 37 times more carbon dioxide than standing waters annually, according to a comprehensive analysis. The finding matters for climate accounting and water infrastructure planning, since hydroclimate and landscape conditions create vast differences in emissions—suggesting one-size-fits-all climate policies will miss the mark.
Originaltitel: Hydroclimate and landscape diversity drive highly variable greenhouse gas emissions from tropical and subtropical inland waters
<p>(Sub)tropical inland waters are important greenhouse gas (GHG) sources, yet limited observations have long hindered broad analyses of GHG variability across this diverse region. Here, through a meta-analysis, we have examined the rates and drivers of GHG emissions from flowing and standing (sub)tropical inland waters. We find considerable spatial variation in fluxes, largely related to differences in hydroclimate, geomorphology, land cover and human disturbance. Flowing waters emit more carbon dioxide (3,387<sub>2,121</sub><sup>5,702</sup> TgCO<sub>2</sub>yr<sup>-1</sup>, expressing median<sub>first quartile</sub><sup>third quartile</sup>), methane (10.6<sub>0.1</sub><sup>28.8</sup> TgCH<sub>4</sub>yr<sup>-1</sup>) and nitrous oxide (0.62<sub>0.35</sub><sup>1.10</sup> TgN<sub>2</sub>Oyr<sup>-1</sup>) than standing waters (114<sub>73</sub><sup>219</sup> TgCO<sub>2</sub>yr<sup>-1</sup>, 5.4<sub>2.1</sub><sup>9.1</sup> TgCH<sub>4</sub>yr<sup>-1</sup> and 0.03<sub>0.02</sub><sup>0.05</sup> TgN<sub>2</sub>Oyr<sup>-1</sup>, respectively). (Sub)tropical inland waters release 4,238<sub>2473</sub><sup>7375</sup> TgCO<sub>2</sub>-equivalents annually, with first- to third-order streams contributing 75% of riverine emissions and lakes larger than 100 km<sup>2</sup> contributing 59% of standing water emissions. Our results suggest emissions from (sub)tropical waters are 29-72% lower than earlier estimates, a downward revision with important implications for global GHG budgets.</p>