Table 2 Global CH4 emissions, carbon burial rates, and offsets in mangroves.

Global emission and carbon burial rates are upscaled to the global mangrove forest area of 137,760 km2 (25). n refers to the number of study site locations (see tables S2, S3, and S5).

CH4 flux rate
(μmol
m−2 day−1)
Global CH4
emission
(Tg CH4
year−1)
Global CH4
emission
(Tg C year−1)
CH4 (CO2 eq.)
emission,
GWP20
(Tg C year−1)
CH4 (CO2 eq.)
emission,
GWP100
(Tg C year−1)
Sequestration
rate (g C m−2
year−1)
Global
carbon burial
(Tg C year−1)
Offset
(%)*
Sensitivity
analysis
offset range
(%)
Water-air
CH4 flux
(n = 9)(n = 9)(n = 9)(n = 9)(n = 9)(n = 27)(n = 27)
Min35.100.0280.0210.660.2656.607.80
Max659.80.5310.39812.454.92651.089.68
Average ± SE288.0 ± 73.20.232 ± 0.0590.174 ± 0.0445.43 ± 1.382.15 ± 0.55227.2 ± 30.6731.30 ± 4.2217.3(15.7–18.5)
Sediment-air
CH4 flux
(n = 14)(n = 14)(n = 14)(n = 14)(n = 14)(n = 27)(n = 27)
Min0000056.607.80
Max2,127.21.711.2840.1415.87651.089.68
Average ± SE391.2 ± 153.40.315 ± 0.1230.236 ± 0.0937.38 ± 2.902.92 ± 1.14227.2 ± 30.6731.30 ± 4.2223.6(22.0–25.8)
Global total(n = 23)(n = 23)(n = 23)(n = 23)(n = 23)(n = 27)(n = 27)
Average ±
scaled error
339.6 ± 106.20.273 ± 0.0530.205 ± 0.0406.41 ± 1.242.53 ± 0.49227.2 ± 30.6731.30 ± 4.2220.5(19.8–21.0)

*Offset is calculated from carbon burial (Tg C year−1) and the CH4 flux using the GWP20 (Tg C year−1).

†Carbon burial (Tg C year−1) and CH4 emissions (GWP20; Tg C year−1) are adjusted up and down by their errors.

‡Accounting for mangrove ecosystems being inundated 50% of the time (water-atmosphere flux) and exposed 50% of the time (sediment-atmosphere flux).