Commented hypothesis Transitioning towards a low carbon economy: Opportunity or complication for sustaining natural capital and ecosystem services? Leen Gorissen Unit Transition Energy and Environment, Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium. Striving towards low carbon societies is high on the global agenda and the progression towards renewable, bio-based resources is steadily emerging. In fact, thinking of genuine sustainability, one may ask the question whether there is an alternative to massive expansion of biomass utilisation over the long haul? In one respect, biomass can be used as a energy carrier that can replace fossilbased resources. It is already clear that biomass resources will be an important part of future energy systems as transport fuels or stationary heat or electricity applications (see WBGU report, 2008). On the other hand, the particular variety and flexibility of biomass use makes it attractive for many other purposes. Such applications of biomass include fibres (additives, paper etc), chemicals (solvents, polymers etc) and materials (textiles, insulation etc). Sectors ranging from architecture over chemistry to cosmetics aim to ‘green’ their image and reduce their footprint and are thus reorienting their resource use from fossil to bio-based materials. Examples include green chemistry, green construction, green and white biotechnology. It is thus no wonder that this versatility of biomass may lead to an increasing tension between sectors, industries and land uses: food versus fuel; bioenergy versus biomaterial and so on. Consequently, the ongoing discussions about a bio-based economy focus predominantly on the marketable roles of biomass whereas the non-marketable goods and services of biomass (e.g. their role in the supporting and regulating ecosystem services) receive little or no attention. In a world with a growing demand for food, energy and materials, society (e.g. agriculture) relies profoundly on these regulatory and supporting ecosystem services while climate change reduces average land productivity and extreme weather events increase vulnerability (IPCC, 2007). In a market driven world, how can massive expansion of biomass production be reconciled with sustaining natural capital and ecosystem services? To guarantee sustainability in a bio-based economy solutions to the trade-offs between the marketable and non-marketable services and goods of biomass resources are urgently needed. Design and establishment of genuinely sustainable systems of the future requires a comprehensive system approach that acknowledges and integrates the perspective of the non-marketable functions and goods of biomass resources in relation to a bio-based economy. To achieve this, biologists, experts in ecosystem services and the like urgently need to participate and take active roles in the existing platforms and fora that are related to a bio-based economy.