Implications of oil depletion for biodiversity

Since the 1950s the growth of the human population and per capita consumption has accelerated, raising concerns about the limits to growth due to resource constraints. The oil supply has been of particular concern, with production predicted to peak in the first decades of the 21st century. This is a problem because modern society is highly dependent on the supply of petrochemicals for its energy, including modern industrialised agriculture. One of the key inputs to agriculture that is dependent on petrochemicals is mineral nitrogen (N), which has increased agricultural yields since 1960s. Constraints to the supply of petrochemicals increase the risk that agriculture will become less productive, requiring more land to maintain food production and threatening biodiversity.This thesis investigates the relationship between the oil supply, food security, global deforestation and biodiversity loss, assessing the worst- and best-case scenarios for agriculture’s footprint without petrochemicals. It also examines the spatial footprint of alternatives to mineral N globally.I used a constraint to the oil supply during the 2007-8 global financial crisis to investigate the dynamics between the oil supply, agriculture’s spatial footprint and the impact on biodiversity. I found that the rate of forest loss increased 29% during this period, and that as a result an additional area of forest the size of Italy was lost. This loss tended to occur in areas of remnant forest with higher biodiversity. I investigated the likely drivers of forest conversion and found that agricultural extensification and the production of renewable energy were probable contributors, but land grabbing by foreign countries to secure food supplies was not. I also found examples of successful policy implementation in Amazonian Brazil and in Australia which had resisted these changes.To investigate the potential threat from agricultural expansion associated with constraints to petrochemical supply, I looked at worst- and best-case scenarios. For the worst-case, I estimated the area that would be required for crop production without petrochemical-based nitrogen fertiliser using N-use efficiency data and current yields. I then spatially modelled cropland expansion globally and the impact this would have on biodiversity and food security. Without mineral N there was insufficient cropland to meet global food needs with many regions experiencing food insecurity. Cropland would expand onto the remaining fertile land leaving largely poor quality habitat for biodiversity.In the best-case scenario, I identified the N source with the smallest footprint by comparing the most land-efficient renewable energy sources to power the Haber-Bosch process and organic sources of N. Solar power was significantly more land efficient than the alternatives. The worst-case option of using no mineral N fertiliser would require about 2000 times the land area and would have about 81,000 times the impact on biodiversity. Although solar energy is the most land-efficient way of powering renewable N, there are constraints on its use. I prioritised alternative N sources globally taking into account impacts and resources available. Some regions would have access to a range of renewable sources of N without major impacts, but Europe has limited options.In conclusion, the global energy supply has the potential to influence the land area required for agriculture through land-fertiliser substitution, and this process impacts on biodiversity. Currently, N-use decisions are made by landholders for largely economic reasons. Conservation science needs to take an interest in the N supply in order to mitigate these impacts, particularly in regions of high biodiversity.