Carbon Stock Potential of Agroforestry Systems in Savannah West Africa: A Case Study of Agroforestry Parkland in Burkina Faso.

Abstract

Agroforestry plays an important role in food security and farmer‘s resilience to climate change and variability in West Africa. However, the link between agroforestry parkland profiles and the capability of these parklands to sequester carbon are not well known. Therefore, agroforestry parkland profiles in three climatic zones of Burkina Faso were studied. Thirty (30) farmlands in each of the climatic zones representing about 35 ha were randomly selected and systematic woody species inventory and dendrometry data were collected. Diameter classes‘ distribution and agroforestry parkland typologies using Importance Value Index analysis were done for agroforestry parkland profiling purpose. The mean tree canopy cover and tree cover in the farms were calculated and three principal crops (millet, red sorghum and white sorghum) yield were used to estimate the trade-off using the mean tree canopy cover as the potential for no cropping area. Non-destructive method of fitted allometrics equations were used to compute carbon stock and to estimate equivalent dioxide carbon. Sustainability analysis of carbon sequestration potential was done using ]0-10], ] 10-40] and ]40-110 cm] diameter classes as long , medium and short term capability of agroforestry parklands to sequester the carbon respectively. The balance between marketable carbon value and the trade-off resulting from tree conservation and the major crops (millet, red sorghum and white sorghum) value were also analysed. The results showed 42 woody species in Sudanian, 31 Sudan-Sahel and 34 Sahel strict zones with corresponding density of 37, 30 and 35 trees/ha respectively. Agroforestry parklands in Sudan-Sahel zone appeared to be unstable compared to the two others climatic zones. Mono-woody species parkland of Vitellaria paradoxa was observed in the Sudanian zone while multi-woody species parklands were observed in the Sudan-Sahel and Sahel strict zones. Moreover, mean tree canopy cover observed was 66.25 m2 in Bouroum-Bourom, 59.92 m2 in Sapouy and 42.1 m2 in Ouahigouya . The average tree cover was 23.99% in Bouroum-Bouroum, 18.23% in Sapouy and 14.88% ix in Ouahigouya. This represents a loss in grain production of 109.5 kg/ha in Bouroum-Bouroum, 247.6 kg/ha in Sapouy and 252.8kg/ha in Ouahigouya. Carbon stock analysis revealed 24.71± 5.84 tCO2ha-1, 28.35± 5.84 tCO2ha-1 and 33.86±5.84 tCO2ha-1 in Ouahigouya, Sapouy and Bouroum-Bouroum respectively. Ouahigouya earned the first place for long term carbon sequestration potential with 1.82% of total amount of carbon. The medium term analysis gave the first place to Sapouy with 71.71% of total amount of carbon and the short-term analysis gave the first place to Ouahigouya with 68.03%. The marketable carbon value was less than the trade-off value resulting from tree keeping and crop production value. The balance analysis revealed that carbon payment system promoted by REDD+ initiative will be profitable and compensable to smallholder farmers effort to keep tree when the tCO2 ha-1 price will be around US$ 4. Both the density of tree (trees/ha) and the number of species constituting the agroforestry parklands have a direct impact of carbon stock potential. A higher tree cover implies a higher trade-off in the agroforestry parkland and suggests reduction in tree density. When considering farmers‘, interest, profitability on carbon market will be the most relevant incentive method to enhance carbon sequestration in agroforestry parkland in order to meet Paris agreement (2015) goals.