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Sedentary extensive small ruminant farming systems are highly important for the preservation of High Nature Value (HNV) farmland. Both the abandonment of grazing and overgrazing have led to environmental degradation in many Mediterranean regions. On the Greek island of Samothrace, decades of overgrazing by sheep and goats has caused severe degradation of local ecosystems. The present study highlights the importance of regional contexts for national and EU agricultural policies in regard to sustainable development of sedentary extensive livestock systems. By utilizing the conceptual framework of socio-ecological systems research, we analyze the interdependencies of environmental, economic and social factors on a local island level. Results show that between 1929 and 2016, the livestock and land-use system of Samothrace transformed from a diverse system towards a simplified system, solely used for small ruminant production. Total livestock units increased from 2200 in 1929 to 7850 in 2002, declining to 5100 thereafter. The metabolic analysis conducted for the years 1993&ndash, 2016 shows that 80&ndash, 90% of the feed demand of small ruminants was covered by grazing, exceeding available grazing resources for at least a decade. The regional implementation of CAP (Common Agricultural Policy) continues to support excessively high animal numbers, while farmers are highly dependent on subsidies and find themselves in an economic deadlock.

Second generation biofuels (2G biofuels) produced from lignocellulosic biomass are often considered as integral part of a future sustainable transport system. Provided that substantial areas of agricultural land can be diverted from food and feed production without impairing food security, energy plantations managed in short rotation appear as a promising option for supplying large amounts of biomass feedstock. However, instead of using agricultural land for energy plantations, it could also be reforested, thereby acting as a long-term carbon (C) sink that also results in climate benefits. This paper provides a systematic comparison of the long-term C benefits from 2G biofuels produced from plantation biomass with the C sink strength of natural succession on arable land (i.e. renaturation). C benefits of the two options are calculated on a per-km2 basis. The dynamics of C accumu-lation in natural vegetation as well as plantations (i.e. biomass yields) strongly depend on site-specific natural conditions. We apply a global perspective and assume that the considered area is distributed among ecological zones and climate zones exactly like actual global cropland areas. To this end, global raster data (5 arc minutes resolution) on cropland distribution, ecosystem and climate zones are merged, and representative C accumulation curves for renaturation in 11 world regions and on global scale are derived. Due to uncertainties with regard to biomass yields of energy plantations, harvest losses and future conversion efficiencies of 2G biofuel processes, a Monte Carlo simulation is carried out with these parameters being varied in ranges derived from literature data. Results show that natural succession is highly likely to be superior (i.e. to result in higher C benefits) for timeframes up to 50 years. Hence, it takes more than 50 years of continuous land use as short rotation plantation and substitution of fossil fuels with 2G biofuels until this alternative results in higher cumulated C benefits than renaturation. This finding is robust to uncertainties related to yields and technological progress in 2G biofuel production. We conclude that allowing agricultural land to revert to its natural state must seriously be considered as low-cost climate mitigation strategy and alternative to biofuel production.

Short rotation plantations are often considered as holding vast potentials for future global bioenergy supply. In contrast to raising biomass harvests in forests, purpose‐grown biomass does not interfere with forest carbon (C) stocks. Provided that agricultural land can be diverted from food and feed production without impairing food security, energy plantations on current agricultural land appear as a beneficial option in terms of renewable, climate‐friendly energy supply. However, instead of supporting energy plantations, land could also be devoted to natural succession. It then acts as a long‐term C sink which also results in C benefits. We here compare the sink strength of natural succession on arable land with the C saving effects of bioenergy from plantations. Using geographically explicit data on global cropland distribution among climate and ecological zones, regionally specific C accumulation rates are calculated with IPCC default methods and values. C savings from bioenergy are given for a range of displacement factors (DFs), acknowledging the varying efficiency of bioenergy routes and technologies in fossil fuel displacement. A uniform spatial pattern is assumed for succession and bioenergy plantations, and the considered timeframes range from 20 to 100 years. For many parameter settings—in particular, longer timeframes and high DFs—bioenergy yields higher cumulative C savings than natural succession. Still, if woody biomass displaces liquid transport fuels or natural gas‐based electricity generation, natural succession is competitive or even superior for timeframes of 20–50 years. This finding has strong implications with climate and environmental policies: Freeing land for natural succession is a worthwhile low‐cost natural climate solution that has many co‐benefits for biodiversity and other ecosystem services. A considerable risk, however, is C stock losses (i.e., emissions) due to disturbances or land conversion at a later time., How can spare cropland be used more efficiently in terms of climate change mitigation? By growing short rotation coppice for bioenergy or allowing cropland to revert to its natural state. We show that the more beneficial option depends on the timeframe considered, biophysical conditions in the considered region, upstream emissions of fuel supply, and the efficiency of the particular bioenergy route in displacing fossil fuels.