Terrestrial Carbon Stock Assessment of Guinea Savanna Woodlands in Kwara and Kogi States

Guinea savanna woodlands represent a significant but underestimated carbon stock in West Africa, with carbon sequestration potential that can contribute to Nigeria's nationally determined contribution targets under the Paris Agreement. In Kwara and Kogi States, within Nigeria's North Central geopolitical zone, guinea savanna woodlands face progressive degradation from charcoal production, agricultural expansion, and livestock overgrazing. This study assesses above-ground and below-ground carbon stocks across a gradient of woodland degradation levels in Kwara and Kogi States, using field-based biomass sampling and allometric equations calibrated for West African savanna systems. A total of 120 sample plots were established across four degradation categories from intact woodland to open degraded shrubland. Soil organic carbon was measured from cores at three depths at each plot. Above-ground biomass carbon in intact woodland averaged 78 tonnes per hectare, declining to 12 tonnes per hectare in severely degraded shrubland. Soil organic carbon showed a less pronounced but significant gradient, declining from 45 to 28 tonnes per hectare between intact and degraded categories. Total carbon stocks in intact guinea savanna are substantially higher than previously estimated in regional carbon accounting frameworks. The study recommends the revision of Nigeria's default woodland carbon factors for REDD+ reporting and the prioritization of woodland degradation prevention as a cost-effective climate mitigation strategy. Keywords: carbon stocks, Guinea savanna, Kwara State, Kogi State, North Central Nigeria