Tracking carbon and biodiversity in shifting cultivations systems in the Eastern Arc Mountains, Tanzania: Six years later

Background/Question/Methods

Shifting cultivation systems are still an important component of tropical montane landscapes but their contribution to providing and maintaining important ecosystem services is little understood. This study looks specifically at the role of fallows within shifting cultivation systems in providing carbon sequestration, carbon storage, and biodiversity conservation services in the long-term and the effect of landuse history and time on the these services.  It also explores the potential to introduce incentive-based mechanisms to improve landuse practices that most threaten the fast recovery of fallows and the maintenance of corridors between forest fragments to maintain biological diversity. Using a chronosequence approach, biomass and biodiversity surveys were conducted between 2007 and 2008 in more than 130 plots (0.1 ha size) consisting of fallows ranging from 1 to 52 years of age along a 1300 altitudinal range in the South Nguru Mountain block of the Eastern Arc Mountains, Tanzania. Six years later (in 2013), the same plots were visited to monitor biomass and biodiversity and determine net ecosystem service changes in that time. 

Results/Conclusions

Preliminary results indicate a drastic drop in carbon storage capacity of the agricultural landscape due to high incidence of fallow conversion to productive land. More than 50% of 2007/2008 fallows were being cultivated in 2013, while very few plots could be found that had been abandoned or left to fallow in the same time period. Plant diversity across the fallows had dropped substantially, mostly due to removal of older fallows. The results indicate a tendency towards reduced fallow periods and increased cultivation duration suggesting a shift towards permanent agricultural systems. Given the fragmented landscapes, such a shift heralds decreased capacity of the landscape to provide the habitat necessary to maintain high levels of biodiversity outside forest reserve areas and increases the opportunity costs for implementing incentive-based mechanisms such as payments for ecosystem services. The results are being used to explore appropriate intervention options for conservation and local development.