Increased nitrogen enrichment and shifted patterns in the world’s grassland: 1860–2014

Abstract

<p><strong>Abstract.</strong> As the largest sector on the Earth’s land surface, the livestock system is not only a major contributor to global manure excreta that perturbs the global nutrient balance, but also a major emitter of greenhouse gases that warms the climate. Much attention has been paid to nitrogen (N) fertilizer and manure N applications to global croplands, however, there is still a lack of spatially-explicit estimates of continuous time-series datasets of manure and fertilizer N inputs in global grasslands. In this study, we therefore developed three global gridded datasets at a resolution of 0.5 degree<span class="thinspace"></span>&amp;times;<span class="thinspace"></span>0.5 degree for the period 1860&amp;ndash;2014 (i.e., annual manure N deposition rate, synthetic N fertilizer use rate, and manure N application rate) by combining annual and 5-arc minute spatial data on pasture and rangeland with country-level manure and synthetic fertilizer N data from the Food and Agricultural Organization database (FAOSTAT). We found that total N inputs, sum of manure N deposition, manure and fertilizer N application to global grassland systems increased from 15.5 to 103.8<span class="thinspace"></span>Tg<span class="thinspace"></span>N<span class="thinspace"></span>yr^&amp;minus;1 during 1860&amp;ndash;2014. Manure N deposition accounted for 83.7<span class="thinspace"></span>% of the total N inputs, whereas manure and fertilizer N application accounted for 7.7<span class="thinspace"></span>% and 8.6<span class="thinspace"></span>%, respectively, during 2000&amp;ndash;2014. At the regional scale, hotspots of manure N deposition remained the same during 1860&amp;ndash;2014 (i.e., southern Asia, Africa, and South America), but hotspots of manure and fertilizer N application have shifted from Europe to southern Asia in the early 21st century. These three datasets could fill data gaps of N inputs in global and regional grasslands and serve as input drivers for ecosystem and biogeochemistry models to investigate the impacts of N enrichment on the global grassland system, greenhouse gas emissions, and environmental sustainability. Datasets available at <a href="https://doi.pangaea.de/10.1594/PANGAEA.892940" target="_blank">https://doi.pangaea.de/10.1594/PANGAEA.892940</a>.</p>