Methane emissions from rice cultivation in West Africa and compensation options from nature reserve forests

Methane (CH$_4$) is a major and potent greenhouse gas (GHG), and its emissions from agricultural
activities, particularly rice cultivation, are a significant concern for climate change. Due to the high
demand for food security, driven by rapid population growth and national initiatives to reduce
dependency on rice imports, rice cultivation is intensified in West Africa. However, its contribution
to atmospheric CH$_4$ remains largely unknown. Here, for the first time, cutting-edge eddy
covariance tower measurements were conducted parallelly in a rice field (Janga) and a reserve
forest (Mole National Park), both located in the Guinea savanna region of West Africa. Using CH$_4$
measurement data from June to October 2023 (rice cultivation period), the dynamic interplay
between methane emissions from rice cultivation and its potential mitigation through forest
methane uptake was assessed. Our results show that the rice field acted as a net source of CH$_4$ at a
rate of 2037 mgCH$_4$m$^{−2}$, whereas the most intense flooded period (August) accounted for 70% of
the total emissions. On the other hand, the forest reserve acted as a sink, with a net uptake of
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−560 mgCH$_4$m$^{−2}$, and the highest uptake observed in October. Accounting for the global
warming potential (GWP) of CH$_4$ over a 20 year period, the forest had a wet season negative GWP
of −47.04 gCO$_2$eq, while the rice field emitted CH$_4$ of 171.36 gCO$_2$eq. This implies that under
similar conditions during the measurement campaigns, the forest per square area needs
approximately a factor of ∼4 to balance the positive radiative effect per square area of rice
cultivated. This work emphasizes the need to integrate forests to compensate for methane released
by rice cultivation in the semi-arid West African savannah region.