Impact of lifestyle, human diet and nutrient use efficiency in food production on eutrophication of global aquifers and surface waters

A spatially explicit (0.5 degree resolution) analysis is presented of the impact of human lifestyle, diet and nutrient use efficiency in food production and wastewater treatment on exceedance of threshold concentrations for nitrate in groundwater, and total N and total P concentrations in surface water, as well as criteria for their ratio. This analysis starts from the middle-of-the-road (SSP2) and the sustainability (SSP1) Shared Socio-economic Pathways (SSP), focusing on the year 2050. The scenarios with changed lifestyle assume a reduction of food wastage and a low-meat diet for all world inhabitants, implying large reductions of meat and milk consumption and production in industrialized countries. Scenarios with improved nutrient use efficiencies assume maximum achievable efficiencies under practical conditions. The SSP2 scenario combined with assumptions on lifestyle and human diet leads to improvement in industrialized countries only, and increased levels in many other regions. A strong improvement is achieved in SSP1, but not in many developing countries, and SSP1 combined with changed lifestyle leads to improvement of groundwater and surface water quality in industrialized countries only. Therefore, changed lifestyle needs to be combined with efforts to improve the efficiency in food production systems and wastewater treatment to achieve reductions of the area affected by groundwater contamination and eutrophication of surface waters. Reduction strategies need to find a balance between N and P, since it is easier to reduce N in rivers to levels below the threshold than P.