Drivers of tropical deforestation and forest regeneration in Tanzania

Forest cover change affects ecosystem services including climate and biodiversity. Global efforts to reduce deforestation, and restore forest cover, depend on understanding the rates and drivers of forest cover change. Knowledge gaps are greatest around rates and drivers of forest regeneration, and drivers of deforestation in Africa. Determinants of the rate of biomass and species accumulation in regenerating forests, are also poorly understood. Although deforestation rates have been well-studied, published rates still vary significantly, particularly in African woodlands.

This thesis investigates rates and drivers of deforestation and natural forest regeneration, with a focus on Tanzania, a country with the fifth highest net deforestation, globally. Using innovative, inter-disciplinary methods, the study presents new empirical evidence on rates and drivers of forest cover change. Linking this to policy, the thesis provides new insights on the challenges of using an energy-transition policy, to reduce deforestation.

New datasets show that deforestation exceeds regeneration by >0.5 Mha y-1. Tanzania’s national gross mean annual deforestation rate is calculated at 1.42% or 0.562 Mha y-1 (0.46 – 0.66 Mha y-1) (2010 – 2017). For village land, a land class that excludes protected areas, the gross mean annual deforestation rate is higher, at 1.9% or 0.608 Mha y-1 (0.46 – 0.78 Mha y-1) for the more recent period of 2011 – 2021. The gross mean annual regeneration rate on village land is far lower at 0.0132 Mha y-1 (0.004 – 0.03 Mha y-1) (1987 – 2021).

New evidence is presented that agriculture causes most deforestation (81% of deforestation events), compared with only 12% attributable to charcoal. In regenerating woodlands, agricultural fallows were the most frequent regeneration driver, while biomass and species accumulation were most affected by regeneration time and precipitation.

While forest and energy policies have sought to curb deforestation through an energy transition away from woodfuel, the policies have been ineffective for two reasons. Firstly, they do not address the main deforestation driver, agriculture. Secondly, they have had limited impact on charcoal consumption, with 88% of Dar es Salaam households still using charcoal in 2018.

Reducing deforestation and amplifying natural regeneration both require closer inter-sectoral coordination. With most deforestation occurring on village-owned land in Tanzania, there is an urgent need for more effective strategies to enable communities to retain forest products and services critical to livelihoods.