Department of Ecology and Conservation Biology, Texas A&M University, College Station, TX, USA.
US Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula, MT, USA.
Glob Chang Biol. 2020 Sep;26(9):4841-4853. doi: 10.1111/gcb.15202. Epub 2020 Jul 3.
The vulnerability of rangeland beef cattle production to increasing climate variability in the US Great Plains has received minimal attention in spite of potentially adverse socioeconomic and ecological consequences. Vulnerability was assessed as the frequency and magnitude of years in which net primary production (NPP) deviated >±25% from mean values, to represent major forage surplus and deficit years, for a historic reference period (1981-2010), mid-century (2041-2065), and late-century (2075-2099) periods. NPP was simulated by MC2, a dynamic global vegetation model, driven by five climate projections for representative concentration pathway (RCP) 4.5 and 8.5. Historically, 4-4.7 years per decade showed either NPP surpluses or deficits. The future number of extreme years increased to 5.4-6.4 and 5.9-6.9 per decade for RCP 4.5 and 8.5, respectively, which represents an increase of 33%-56% and 38%-73%, respectively. Future simulations exhibited increases in surplus years to between 3 and 5 years in the Northern Plains and 3-3.5 in the Southern Plains. The number of deficit years remained near historic values of 2 in the Northern Plains, but increased in the Southern Plains from 2.5 to 3.3 per decade. Historically, NPP in extreme surplus and deficit years both deviated 40% from mean NPP in all three regions. The magnitude of deficit years increased by 6%-17% in future simulations for all three regions, while the magnitude of surplus years decreased 16% in the Northern Plains and increased 16% in the Southern Plains. The Southern Plains was the only region to exhibit an increase in the magnitude of both surplus and deficit years. Unprecedented future variability of NPP may surpass the existing adaptive capacity of beef producers and adversely impact the economic viability of rangeland cattle production and ecological sustainability of rangeland resources.
美国大平原地区的牧场肉牛生产对气候变异性增加的脆弱性一直没有得到足够的重视，尽管这可能会带来不利的社会经济和生态后果。脆弱性评估为净初级生产力 (NPP) 偏离平均值 ±25%的频率和幅度，表示主要的饲料过剩和短缺年份，历史参考期（1981-2010 年）、中期（2041-2065 年）和晚期（2075-2099 年）。NPP 由 MC2 模拟，MC2 是一种动态的全球植被模型，由五个代表浓度途径（RCP）4.5 和 8.5 的气候预测驱动。历史上，每十年有 4-4.7 年出现 NPP 过剩或短缺。未来极端年份的数量增加到每十年 5.4-6.4 和 5.9-6.9 年，分别代表 RCP 4.5 和 8.5 的增长 33%-56%和 38%-73%。未来模拟显示，北部平原的盈余年份增加到 3-5 年，南部平原增加到 3-3.5 年。北部平原的赤字年份仍接近历史值 2 年，但南部平原从每十年 2.5 年增加到 3.3 年。历史上，所有三个地区极端过剩和短缺年份的 NPP 都偏离了平均 NPP 的 40%。未来模拟中，所有三个地区的赤字年份的幅度增加了 6%-17%，而盈余年份的幅度减少了 16%在北部平原，在南部平原增加了 16%。南部平原是唯一一个盈余和赤字年份幅度都增加的地区。NPP 的前所未有的未来变异性可能超过肉牛生产者现有的适应能力，并对牧场肉牛生产的经济可行性和牧场资源的生态可持续性产生不利影响。
