Aboveground Biomass and CO2 Emissions from Land Use and Land Cover Change in Sudan Savannah Ecological Zone of Ghana

Abstract

Stabilising the global temperature within the predicted 2°C rise, it is necessary to provide accurate information to policymakers on the current state, temporal and spatial changes of CO2 emission from land use and land cover changes which is the main cause of climate change. Above ground biomass (AGB) and land use and land cover (LULC) dynamics are important parameters for carbon stock and CO2 emissions, their accurate assessment is indispensable. This study was carried out in the Sudan savannah ecological zone of Ghana using field inventory and remote sensing to assess and map changes in aboveground biomass, carbon stock and CO2 emissions from land use and land cover change. Land use and land cover changes were analysed using Landsat images (1986, 1999, 2006 and 2016) and random forest classifier. Forest inventory was carried out for trees species at diameter at breast height (dbh) greater or equal to 5 cm and less than 5 cm. Six allometric models were developed for trees with a diameter less than 5 cm (saplings) using diameter, wood density, and height. For biomass mapping, Landsat OLI (2017) was classified and the corresponding biomass value was attributed to the corresponding LULC class. The net CO2 emission from land use and land cover changes was estimated and mapped using IPCC Tiers 3 emission factor and activity data choice. The results generated from land use and land cover analysis from 1986 to 2016 showed a reduction in forest land, shrubs/grassland, and water. Whereas, cropland and settlement exhibited a rise in the entire area. However, the substantial decrease in forest cover, as well as the greatest increase in cropland and settlement, was observed in Bawku and Pusiga. In addition, based on Cellular automata projection, cropland will still be the major land use and land cover class in Bawku, Binduri, Garu, and Pusiga. On the other hand, forest, shrubs/grassland, and water will still be decreasing in 2036. The total aboveground biomass recorded was 48.51 Mg ha-1 which translates into 22.80 Mg C ha-1 v of carbon content and 75.14 Mg CO2 ha-1 of CO2 equivalent. The greatest value of aboveground biomass was recorded in cropland (48%), next to forest land (33%) and shrubs/grassland (19%). At the District level, the highest amount of AGB was observed in Bawku Municipality (45%), followed by Garu (25%), Binduri (18%) and Pusiga (12%). An overall amount of 383,306 t CO2 or 67% could be released to the atmosphere. An estimated -186,304 t CO2 or 33% was sequestered during the past three decades. The inter-annual statistics (1986 - 1999 and 1999 to 2006), as well as the past decade (2006- 2016), exhibited a reduction in CO2 emissions contrary to the removals. In the future, the amount of CO2 released to the atmosphere as well as the removals will be increased by 2036 using the business-as-usual scenario. Through the land use/land cover maps, it was noticed that carbon was sequestered in areas where forest and/or shrubs/grassland has been converted to cropland. The outcome of this work could contribute to carbon accounting and efficient environmental management in the Sudan savannah zone of Ghana.