Large-scale second-generation bioenergy production with carbon capture and storage (BECCS) is considered a crucial component in many climate change mitigation pathways limiting global warming to 1.5–2 °C. However, land requirements for lignocellulosic cropland expansion could pose threats to the Sustainable Development Goal (SDG) agenda. Two major concerns regarding impacts of land-use changes are potential implications for climate and biodiversity. Yet, with regards to bioenergy, these two areas remain relatively understudied, largely due to a lack of suitable data resources and the overall complexity involved in calculating these impacts. As a result, most literature on land-use impacts of bioenergy focuses on present day first-generation bioenergy cropland and/or tends to be at the regional or local scale. The aim of this thesis is to explore the global impacts of large-scale bioenergy deployment (300 EJyr-1 by 2100) on climate and biodiversity, in the aims of furthering our knowledge of bioenergy’s role within SDGs 13: “Climate Action”, and 15: “Life on Land”. By implementing sophisticated land-use scenarios into an Earth system climate model and two species richness models, this work identifies potential biogeochemical and biogeophysical climate effects and biodiversity impacts resulting from global cultivation of second-generation energy cropland over the 21st century. At the global scale, findings suggest major climate benefits from large-scale BECCS production, whereby substitution of fossil fuel emissions via BECCS leads to a cooling effect (–0.44 °C by 2100) which is significantly dominant over the biogeochemical warming effect from land conversion (+0.0087 °C by 2075–2100). At the regional scale, however, both biogeochemical and biogeophysical climate effects are more significant (reaching up to 0.1 °C and -0.09 °C in some regions by 2075–2100, respectively) and vary widely across the globe, influenced by changes in polar amplification, soil carbon, surface albedo, evapotranspiration, sensible and latent heat fluxes, and soil temperatures. Bioenergy expansion is also expected to cause significant habitat loss in biodiversity hotspots, particularly across tropical regions of Africa, Asia, and Latin America, with the largest numbers and percentages of endemic species extinctions occurring in Madagascar and the Philippines, respectively. Mexico contains the highest number of threatened endangered and critically endangered species in comparison to all other countries, accounting for more than half of the total species impacted by cropland expansion in North America. In total, approximately 12,300–15,500 endemic species and 557 endangered and critically endangered species are expected to be lost due to second-generation bioenergy production by 2100. Sustainability measures will be needed alongside large-scale bioenergy deployment to combat potential trade-offs with sustainability goals. For instance, water protection and forest conservation policies can be implemented to reduce unsustainable water withdrawals and deforestation. However, findings in this work indicate that, while global impacts of water protection on land-use changes are small, the expansion of non-irrigated rainfed cropland into nearby forests could cause further threats to biodiversity and exacerbate biogeophysical climate effects. Site-specific understanding of human and environmental water consumption, increased irrigation efficiency through improvements in water storage and transport, and better land management practices can help increase yields and reduce the need for large areas of rainfed cropland. On the other hand, implementation of a global forest protection scheme (REDD+) significantly reduces implications of bioenergy expansion for both climate and biodiversity. Although, cropland ‘leakage’ onto other equally biodiverse ecosystems may occur. Furthermore, current conservation initiatives tend to focus on reductions in greenhouse gas emissions, often overlooking the broader range of ecosystem services provided by forests, such as biogeophysical effects (e.g., water regulation, soil protection), ecological functions, and cultural values. Sustainable delivery of second-generation bioenergy will require a more holistic representation of these ecosystem services in future land management and conservation schemes, aided by shared knowledge between local stakeholders (e.g., landowners, local governments, and indigenous communities), researchers, and policy advisors.
