Reducing deforestation can generate multiple economic, social and ecological benefits by safeguarding the climate and other ecosystem services provided by forests. Understanding the relative contribution of different drivers of deforestation is needed to guide policies seeking to maintain natural forest cover. We assessed 119 randomly selected plots from areas deforested between 2010 and 2017, in Tanzania. Through ground surveys and stakeholder interviews we assessed the proximate deforestation drivers at each point. Crop cultivation was the most commonly observed driver occurring in 89% of plots, compared to livestock grazing (69%) and charcoal (35%). There was evidence of fire in 77% of plots. Most deforestation events involved multiple drivers, with 83% of plots showing signs of two or more drivers. Stakeholder interviews identified agriculture as the primary deforestation driver in 81% of plots, substantially more than charcoal production (12%), timber harvesting (1%) and livestock (1%). Policy-makers in Tanzania have sought to reduce deforestation by reducing demand for charcoal. However, our work demonstrates that agriculture, not charcoal, is the main driver of deforestation in Tanzania. Beyond protected areas, there is no clear policy limiting the conversion of forests to agricultural land. Reducing deforestation in Tanzania requires greater inter-sectoral coordination between the agriculture, livestock, land, energy and forest sectors.

Scientific understanding of the role of development in conservation has been hindered by the quality of evaluations of integrated conservation and development projects. We used a quasi-experimental design to quantitatively assess a conservation and development project involving commercial butterfly farming in the East Usambara Mountains of Tanzania. Using a survey of conservation attitudes, beliefs, knowledge, and behavior, we compared 150 butterfly farmers with a control group of 170 fellow community members. Due to the nonrandom assignment of individuals to the two groups, we used propensity-score matching and weighting in our analyses to control for observed bias. Eighty percent of the farmers believed butterfly farming would be impossible if local forests were cleared, and butterfly farmers reported significantly more participation in forest conservation behaviors and were more likely to believe that conservation behaviors were effective. The two groups did not differ in terms of their general conservation attitudes, attitudes toward conservation officials, or knowledge of conservation-friendly building techniques. The relationship between butterfly farming and conservation behavior was mediated by dependency on butterfly farming income. Assuming unobserved bias played a limited role, our findings suggest that participation in butterfly farming increased participation in conservation behaviors among project participants because farmers perceive a link between earnings from butterfly farming and forest conservation.

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Rates and drivers of natural forest regeneration are areas of uncertainty for policy, forest management and climate change mitigation. In this study, the rate of deforestation and the rate and drivers of natural regeneration are described for 56 million hectares of village land in Tanzania, a country undergoing rapid deforestation. To determine the regeneration and deforestation rates, remote sensing (RS) data for 500 randomly selected points were reviewed for a 34 year period from 1987 to 2021 using Google Earth Engine. Over this period, regeneration, involving a transition from forest to non-forest and back to forest was detected on 4.8% of village land (95% CI: 3.1%–7.1%), while 0.8% of land transitioned from non-forest to forest (95% CI: 0.2%–2.04%). 22% of village land was deforested (95% CI: 18.6%–26.1%), equivalent to a mean annual net loss of 0.35 million hectares of forest. Using a combination of RS data, field plots and structured interviews, the land cover change trajectories of 180 regenerating plots, in 10 sampling clusters, were assessed to identify regeneration drivers and assess biomass and tree species accumulation rates. Agricultural fallows are the regeneration driver in 47% of plots (95% CI: 39.8%–54.8%). Other common regeneration drivers include abandonment of cultivated areas for reasons apart from fallowing, conservation and post wood-extraction abandonment in 19% (95% CI: 13.9%–26%), 18.3% (95% CI: 13%–24.8%) and 12.8% (95% CI: 8.3%–18.6%) of plots, respectively. The mean carbon sequestration rate was 1.4 Mg C ha−1 y−1, equivalent to 4.3 Tg C y−1 (95% CI: 3.9–4.7 Tg C y−1) across the 3.15 million hectares of regenerating village land forest. The mean species accumulation rate was 1.08 species y−1 (95% CI: 1.0–1.2). Regeneration time, location and precipitation have the greatest influence on biomass and species richness. The study highlights the potential for natural regeneration to contribute to global and national climate and biodiversity goals and to sustainable, productive forest management. The importance of cooperation and policy-alignment between the forest, agriculture and land sectors are under-scored.