Estimating Aboveground Biomass Changes in the Semi-Deciduous Forest Zone of Togo over the Last 30 Years

Aboveground biomass changes estimated at the landscape level are necessary for estimating carbon pools in forest and provide baseline data for future studies. The objective of this study is to combine national forest inventory and remote sensing data to: (1) generate aboveground biomass maps for time-series between 1991 and 2018 and (2) analyze changes in aboveground biomass during the following years 1991, 2003 and 2018. AGB maps across semi-deciduous forest zone of Togo were produced using time-series from freely available Landsat images in combination with a data set of field measurement from national forest inventory (NFI). The results showed a strong positive relationship between AGB change map aggregated in classes of 75 Mg/ha and forest cover map. These comparisons provide strong evidence to validate the approach and associated map. The net annual rate of aboveground biomass loss is estimated to be 0.45% between 1991 and 2003 and 0.31% between 2003 and 2018. More than 48% of forest loss occurred in land with AGB <75 Mg/ha, being particularly prevalent in already fragmented agricultural landscapes. Moreover, result showed that in 2018, nearly 69% of forest’s area are distributed in savanna woodlands, woodland and young secondary forests that contain low biomass (AGB < 150 Mg ha−1) compared to 67% in 1991. This study is a reliable, cost-effective and reproducible approach to map AGB changes in complex and dynamic forest landscapes and can support policy approaches towards reducing emissions from deforestation and forest degradation (REDD+).