J. Geogr. Sci. 2018, 28(11): 1567-1579 DOI: https://doi.org/10.1007/s11442-018-1561-2 © 2018 Science Press Springer-Verlag Received: 2017-02-20 Accepted: 2017-09-15 Author: Eisner Rowan, E-mail: re338@cam.ac.uk www.geogsci.com www.springerlink.com/content/1009-637x Global prioritisation of renewable nitrogen for biodiversity conservation and food security Eisner ROWAN 1 , SEABROOK Leonie 2 , MCALPINE Clive 2 1. University of Cambridge Conservation Research Institute, Cambridge CB2 3QZ, UK; 2. Centre for Biodiversity and Conservation Science, UQ, QLD 4072, Australia Abstract: The continuing use of petrochemicals in mineral nitrogen (N) production may be affected by supply or cost issues and climate agreements. Without mineral N, a larger area of cropland is required to produce the same amount of food, impacting biodiversity. Alternative N sources include solar and wind to power the Haber-Bosch process, and the organic options such as green manures, marine algae and aquatic azolla. Solar power was the most land-efficient renewable source of N, with using a tenth as much land as wind energy, and at least 100th as much land as organic sources of N. In this paper, we developed a decision tree to locate these different sources of N at a global scale, or the first time taking into account their spatial footprint and the impact on terrestrial biodiversity while avoiding impact on albedo and cropland, based on global resource and impact datasets. This produced relatively few areas suitable for solar power in the western Americas, central southern Africa, eastern Asia and southern Australia, with areas most suited to wind at more extreme latitudes. Only about 2% of existing solar power stations are in very suitable locations. In regions such as coastal north Africa and central Asia where solar power is less accessible due to lack of farm income, green manures could be used, however, due to their very large spatial footprint only a small area of low productivity and low biodiversity was suitable for this option. Europe in particular faces challenges because it has access to a relatively small area which is suitable for solar or wind power. If we are to make informed decisions about the sourcing of alternative N supplies in the future, and our energy supply more generally, a decision-making mechanism is needed to take global considerations into account in regional land-use planning. Keywords: concentrated solar; ammonia synthesis; biofixation 1 Introduction Modern agriculture is highly dependent on petrochemicals, especially for nitrogen (N) fer- tiliser which is made using natural gas. The use of petrochemicals to produce fertiliser is unsustainable for two main reasons. First, they are non-renewable and consumption is growing faster than the supply due to both growth in human populations and per capita con- sumption with increased living standards (Kruger, 2006). Second, their use emits greenhouse