Demographic impacts of harvesting non-timber forest products from an African mahogany species

Non-timber forest products (NTFPs) are considered to be sustainable alternatives to timber logging in terms of conserving tropical forest. However, given the large number of cases of unsustainable harvest reported in the tropics, assessing the impact of NTFPs extraction on the persistence of harvested populations is key to ensuring sustainability. We assessed the impacts of combined harvest of foliage and bark on the demography of Khaya senegalensis (Meliaceae) in two contrasting ecological regions of Benin, West Africa.  K. senegalensis trees were monitored over three years in three heavily harvested and three no/less harvested populations within each ecological region (Sudanian versus Sudano-Guinean regions). Matrix population models were used to assess the impacts of harvest and ecological variation on the finite rate of growth (λ). Perturbation analysis was used to investigate the contribution of population vital rates to the variation in λ between ecological regions and harvesting intensities. λ values were less than one only in the Sudanian region indicating population decline. In the Sudano-Guinean region, heavily harvested populations had lower λ values than did low harvested populations. Difference in λ values between ecological regions was due to differences in growth of sapling and vegetative life stages. However, differences in adult fecundity and fertility were responsible for the variation in λ values between populations subject to different harvesting intensities in the Sudano-Guinean region. Increasing the survival of adult trees would contribute the most to K. senegalensis persistence. Management policies to promote lower harvesting pressure in the Sudanian region by encouraging community Ðrun plantations and increasing harvesters' education should be promoted.