CNH: Spontaneous Silviopastoral Landscapes: Origins, Extent, and Ecological Significance in the Ecuadorian Amazon

随着全球热带森林面积的持续减少，农业景观现在覆盖了大约50%的热带生物群。了解和影响热带生物多样性的能力在很大程度上取决于对积极管理的地貌的基本了解。由于牧场覆盖了中美洲和南美洲新热带地区的大部分农田，其生物多样性的重大变化，如出现更多的树木，是一个潜在的重要发展。厄瓜多尔亚马逊盆地牧场上的树木数量在过去20年里似乎有所增加。这些森林草原景观是自发产生的，没有人努力去创造它们。这一跨学科研究项目将调查这一变化的生态和人类相关性。接近森林残留物、土壤质量和物种特征对牧场树木的传播起着重要作用，管理做法似乎也很重要。通过对树木数量不同的牧场进行深入研究，研究人员将研究种子雨、土壤肥力、树种和觅食如何影响牧场树木的传播，以及随着牧场树木的增加，生物多样性、碳储存和生物地球化学循环如何变化。通过与牧场所有者的面谈，调查人员将评估一种假设，即希望经济多样化的小农户可以容忍牧场上更多的树木，因为他们没有劳动力来做其他事情。小农户不会放弃养牛，因为牛的收入太重要了，不能放弃，但因为他们现在有非农业的追求，他们没有时间像他们全职与牛一起工作时那样彻底地“清理”牧场的苗木。由于中年男性离开家到其他地方工作，女性户主现在管理着更多的牧场，她们以一种尖锐的方式面临着这些困境。由于没有居住的男性或土地的完整所有权，妇女担心土地被入侵，因此她们通过在土地上放牧来维持土地上的“存在”。与此同时，妇女把照看孩子和在家做针线活结合起来谋生，所以她们没有时间清理牧场的苗木。一旦建立起来，这些树就会创造出允许其他树木发芽的微环境。调查人员将通过牧场生态清单、对农民的采访、航空照片和厄瓜多尔亚马逊地区90个养牛场的卫星图像来评估这些假设。利用这些来源的数据和信息，他们将建立一个模型，在这个模型中，社会和生态变化产生自发的森林草原景观。在新热带地区以前的森林覆盖的大片地区，出现了一条自发的通往森林草原景观的道路。这一“自然”历史可能会对长期但相对不成功的促进森林草原景观的努力产生重要影响。在政客们考虑为环境服务买单的背景下，这是一项更大的国际努力的一部分，目的是在热带森林中封存碳。研究概述了小农户如何在遮荫的牧场封存碳，可以证明如何加快这种景观变化，让贫穷的农民受益。该项目由NSF自然与人类耦合系统动力学(CNH)计划和NSF国际科学与工程办公室支持。

With the continuing decline in the global extent of tropical forests, agricultural landscapes now cover roughly 50 percent of the tropical biome. Capabilities to understand and influence tropical biodiversity depend in large part on basic understanding of actively managed landscapes. Because pastures cover most agricultural lands in the neotropics of Central and South America, significant changes in their biodiversity, such as the emergence of more trees, represent a potentially important development. The numbers of trees in pastures in the Ecuadorian Amazon basin appear to have increased during the past two decades. These silvopastoral landscapes have emerged spontaneously, without efforts by people to create them. This interdisciplinary research project will investigate the ecological and human correlates of this change. Proximity to forest remnants, soil quality, and species characteristics play important roles in the spread of trees in pastures, with management practices also appearing to be important. Through intensive study of pastures with variable numbers of trees, the investigators will examine how seed rain, soil fertility, tree species, and foraging influence the spread of trees in pastures as well as how biodiversity, carbon storage, and biogeochemical cycling change with more trees in pastures. Through interviews with owners of the pastures, the investigators will assess the hypothesis that small farmers intent on economic diversification tolerate more trees in pastures because they do not have the labor to do otherwise. Small farmers do not abandon cattle ranching because income from cattle is too important to forego, but because they now have non-farm pursuits, they do not have time to "clean" pastures of seedlings as thoroughly as they did when they worked full time with cattle. Because middle-aged men have left home to work elsewhere, female household heads now manage more pastures, and they face these dilemmas in an acute way. Without resident males or full titles to land, women worry about land invasions, so they maintain a "presence" on the land by grazing cattle on it. At the same time, women combine child care with needlework at home to earn a livelihood, so they do not have time to clean pastures of seedlings. Once established, the trees create micro-environments that allow other trees to sprout. The investigators will evaluate these hypotheses with evidence from ecological inventories of pastures, interviews with farmers, aerial photos, and satellite images of 90 cattle ranches in the Ecuadorian Amazon. Using data and information from these sources, they will build a model in which social and ecological changes generate spontaneous silvopastoral landscapes.A spontaneous path to silvopastoral landscapes has emerged in a large, formerly forested area of the neotropics. This "natural" history may have important implications for the long-standing but relatively unsuccessful efforts to promote silvopastoral landscapes. In a context in which politicians consider paying for environmental services as part of a larger, international effort to sequester carbon in tropical forests, research that outlines how small farmers are sequestering carbon in shaded pastures can demonstrate how to expedite this landscape change and benefit poor farmers. This project is supported by the NSF Dynamics of Coupled Natural and Human Systems (CNH) Program and by the NSF Office of International Science and Engineering.