Abstract
Australia is a warm country with well-developed agriculture and a highly urbanized population. How these specific features impact the nitrogen cycle, emissions, and consequently affect environmental and human health is not well understood. Here, we find that the ratio of reactive nitrogen (Nr) losses to air over losses to water in Australia is 1.6 as compared to values less than 1.1 in the USA, the European Union, and China. Australian Nr emissions to air increased by more than 70% between 1961 and 2013, from 1.2 Tg N yr−1 to 2.1 Tg N yr−1. Previous emissions were substantially underestimated mainly due to neglecting the warming climate. The estimated health cost from atmospheric Nr emissions in Australia is 4.6 billion US dollars per year. Emissions of Nr to the environment are closely correlated with economic growth, and reduction of Nr losses to air is a priority for sustainable development in Australia.
Highlights
The role of global food, fibre, and biofuel production in the disruption of the global nitrogen (N) cycle has attracted much attention, as better quantification of reactive N (Nr, all N forms except N2) losses to the environment have highlighted their impacts on environmental quality, ecosystems, and human health [1, 2]
Nr emitted to the atmosphere through both natural and anthropogenic processes contributes to a range of environmental problems, including ambient air pollution (AAP), stratospheric ozone (O3)
Australia emitted an annual total of 2.1 Tg Nr to the air in 2013, compared to only 1.3 Tg total N (TN) released to water bodies (Figure 1)
Summary
The role of global food, fibre, and biofuel production in the disruption of the global nitrogen (N) cycle has attracted much attention, as better quantification of reactive N (Nr, all N forms except N2) losses to the environment have highlighted their impacts on environmental quality, ecosystems, and human health [1, 2]. With increasing use of mineral fertilizers and fossil fuels, the magnitude of anthropogenic N fluxes contributed to a tripling of total N input to terrestrial ecosystems compared to the preindustrial era [3]. Depletion, global warming, acidification and eutrophication of ecosystems, biodiversity loss, and agricultural and horticultural crop damage [4,5,6,7]. A comprehensive assessment of N use efficiency and Nr emissions is of importance to design strategies to increase sustainability of Australia’s agriculture, as Australia is one of the leading global exporters of wheat, cotton, wool, and beef. From 1961 to 2013, productivity from cropping land in Australia increased fivefold, while N fertilizer consumption increased 36 times [8], indicating risk of substantial Nr losses to the environment and, at the same time, the scope for significant agricultural N efficiency gains. Nearly 100 million cattle and sheep are reared in Australia in 2018 [9], which make Australia the world’s largest red meat exporter by value [10] and emit considerable amounts
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