Tackling societal and environmental challenges requires new approaches that connect top-down global oversight with
bottom-up subnational knowledge. We present a novel framework for participatory development of spatially explicit scenarios at
national scale that model socioeconomic and environmental dynamics by reconciling local stakeholder perspectives and national spatial
data. We illustrate results generated by this approach and evaluate its potential to contribute to a greater understanding of the relationship
between development pathways and sustainability. Using the lens of land use and land cover changes, and engaging 240 stakeholders
representing subnational (seven forest management zones) and the national level, we applied the framework to assess alternative
development strategies in the Tanzania mainland to the year 2025, under either a business as usual or a green development scenario.
In the business as usual scenario, no productivity gain is expected, cultivated land expands by ~ 2% per year (up to 88,808 km²), with
large impacts on woodlands and wetlands. Despite legal protection, encroachment of natural forest occurs along reserve borders.
Additional wood demand leads to degradation, i.e., loss of tree cover and biomass, up to 80,426 km² of wooded land. The alternative
green economy scenario envisages decreasing degradation and deforestation with increasing productivity (+10%) and implementation
of payment for ecosystem service schemes. In this scenario, cropland expands by 44,132 km² and the additional degradation is limited
to 35,778 km². This scenario development framework captures perspectives and knowledge across a diverse range of stakeholders and
regions. Although further effort is required to extend its applicability, improve users’ equity, and reduce costs the resulting spatial
outputs can be used to inform national level planning and policy implementation associated with sustainable development, especially
the REDD+ climate mitigation strategy.