The project introduced the concept "Hidden emissions of forest transitions", proposing that forest recovery in the context of industrialization is enabled by processes outside of forests which cause additional emissions. Further, we advanced reflexions on what sustainable forest use actually means. We advocated for a nuanced perspective that does not focus exclusively on either ecological (e.g. restoration) or social (e.g. wood provision) dimensions alone, but instead integrates the conflicting aims of both. HEFT also contributed to better conceptualizing how international trade of biomass affects climate impacts and sustainability more generally, shedding light on coexisting but diverging methodological approaches, and reflecting on those conditions that make international trade in biomass sustainable - and those that don't.
The project developed accounting methods and models to reconstruct regional, national and global-level forest and ecosystem carbon dynamics and greenhouse gas emissions from agriculture in time periods of 100 to 200 years. This allowed to quantify the climate impact of long-term forest recovery, and to assess major factors that drove these changes. A particularly innovative approach developed in the project was the historical counterfactual analysis. This way, we were able to show, for example, that globally since 1990, gross forest recovery resulted from increased average tree growth rates, rather than from forest area expansion.
The project also made major methodological contributions in conntecting biophysical reconstructions of forest and land-use change with assessments of social and political dynamics that shaped them. We found that the reduction of agricultural practices in forests (e.g. forest grazing in temperate regions and shifting cultivation in the tropics) was an important factor accompanying forest transitions across case studies, coinciding with ecological (i.e. enhanced tree growth) and social dynamics (i.e. reduced access to forests). In addition, we found that efficiency gains in land and resource use were important, but overcompensated by increases in consumption (e.g. more energy use, more livestock product consumption), resulting in growing emissions in the long run.
We identified land sharing strategies, e.g. through agroforestry, as potentially viable land-use options that integrate socially just forest use with reduced climate impacts. Furthermore, we found that changes in the entire supply chain, from production to consumption, are required to allow for ecologically sustainable biomass production to meet human needs. Important levers include reductions in livestock production and consumption and a shift in wood use from bioenergy towards long-lived products.
