Global Rangeland Primary Production and Its Consumption by Livestock in 2000–2010

Authors: Wolf, Julie; CHEN, MIN - University Of Wisconsin; ASRAR, GHASSEM - Universities Space Research Associaton

Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Globally, livestock graze plant biomass from extensive rangeland areas, and grazing provides more than half of total livestock intake. It is difficult to accurately quantify the annual production and consumption of grazable plant biomass, however. Therefore, we used remote sensing and modeling strategies to improve estimates for the years 2000 – 2010. We found that production of plant biomass on global rangelands was stable over the period with small interannual variations, while grazing demand increased each year. The total amount of plant biomass produced in rangelands each year is about ten times larger than total grazing demand, but much of it is unavailable or unpalatable for grazing. We found that deficits occurred every year, increasing from 2.4% of grazing demand in 2000 to an unprecedented 4.3% in 2010. Our findings suggest that rangelands are under significant pressure to accommodate rising grazing demand.

Technical Abstract: Livestock grazing occupies ca. 25% of global ice-free land, removing large quantities of carbon (C) from global rangelands. The proportion of total livestock intake that is supplied by grazing (GP) is estimated at >50%, larger than the proportion from crop- and byproduct-derived fodders. Both rangeland productivity and its consumption through grazing are difficult to quantify, as is grazing intensity (GI), the proportion of annual aboveground net primary productivity (ANPP) removed from rangelands by grazing livestock. We develop national or sub-national level estimates of GI and GP for 2000 – 2010, using remote sensing products, inventory data, and model simulations, and accounting for recent changes in livestock intake, fodder losses and waste, and national cropland use intensities. Over the 11 study years, multi-model-average global rangeland ANPP varied between the values of 13.0 Pg C in 2002 and 13.96 Pg C in 2000. The global requirement for grazing intake increased monotonically from 1.54 in 2000 to 1.82 Pg C in 2010. Although total global rangeland ANPP is an order of magnitude larger than grazing demand, much of this total ANPP is unavailable for grazing, and national or sub-national deficits between intake requirements and available rangeland ANPP occurred in each year, totaling 36.6 Tg C (2.4% of total grazing intake requirement) in 2000, and an unprecedented 77.8 Tg C (4.3% of global grazing intake requirement) in 2010. After accounting for these deficits, global average GI ranged from 10.7% in 2000 to 12.6% in 2009 and 2010. The annually increasing grazing deficits suggest that rangelands are under significant pressure to accommodate rising grazing demand. Greater focus on observing, understanding, and managing the role of rangelands in feeding animals, providing ecosystem services, and as part of the global C cycle, is warranted.