Dotta G, Phalan B, Silva T W, Green R, Balmford A
University of Cambridge, Department of Zoology, Conservation Science Group, Downing Street, Cambridge, CB2 3EJ, United Kingdom.
Current address: Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Laboratório de Ornitologia, sala 112, Avenida Ipiranga, 6681, Porto Alegre, Rio Grande do Sul, Brazil.
Conserv Biol. 2016 Jun;30(3):618-27. doi: 10.1111/cobi.12635. Epub 2015 Dec 11.
Globally, agriculture is the greatest source of threat to biodiversity, through both ongoing conversion of natural habitat and intensification of existing farmland. Land sparing and land sharing have been suggested as alternative approaches to reconcile this threat with the need for land to produce food. To examine which approach holds most promise for grassland species, we examined how bird population densities changed with farm yield (production per unit area) in the Campos of Brazil and Uruguay. We obtained information on biodiversity and crop yields from 24 sites that differed in agricultural yield. Density-yield functions were fitted for 121 bird species to describe the response of population densities to increasing farm yield, measured in terms of both food energy and profit. We categorized individual species according to how their population changed across the yield gradient as being positively or negatively affected by farming and according to whether the species' total population size was greater under land-sparing, land-sharing, or an intermediate strategy. Irrespective of the yield, most species were negatively affected by farming. Increasing yields reduced densities of approximately 80% of bird species. We estimated land sparing would result in larger populations than other sorts of strategies for 67% to 70% of negatively affected species, given current production levels, including three threatened species. This suggests that increasing yields in some areas while reducing grazing to low levels elsewhere may be the best option for bird conservation in these grasslands. Implementing such an approach would require conservation and production policies to be explicitly linked to support yield increases in farmed areas and concurrently guarantee that larger areas of lightly grazed natural grasslands are set aside for conservation.
在全球范围内，农业是生物多样性面临的最大威胁来源，这体现在自然栖息地的持续转变以及现有农田的集约化经营上。土地节约和土地共享被认为是协调这种威胁与粮食生产用地需求的替代方法。为了探究哪种方法对草原物种最具前景，我们研究了巴西和乌拉圭坎普斯地区鸟类种群密度如何随农场产量（单位面积产量）变化。我们从24个农业产量不同的地点获取了生物多样性和作物产量信息。针对121种鸟类拟合了密度-产量函数，以描述种群密度对农场产量增加的反应，产量以食物能量和利润来衡量。我们根据个体物种在产量梯度上种群的变化情况，将其分类为受农业活动正向或负向影响，并根据物种在土地节约、土地共享或中间策略下的种群总数大小进行分类。无论产量如何，大多数物种都受到农业活动的负面影响。产量增加使约80%的鸟类物种密度降低。我们估计，就当前生产水平而言，对于67%至70%受负面影响的物种，包括三种受威胁物种在内，土地节约策略将比其他策略带来更大的种群数量。这表明，在某些地区提高产量，同时在其他地区将放牧强度降低到较低水平，可能是这些草原鸟类保护的最佳选择。实施这种方法需要将保护政策和生产政策明确联系起来，以支持农作区产量增加，同时确保留出更大面积的轻度放牧天然草原用于保护。
