Evaluating spatially explicit sharing-sparing scenarios for multiple environmental outcomes

1. Understanding how to allocate land for the sustainable delivery of multiple, competing objectives is a major societal challenge. The land sharing-sparing framework presents a heuristic for understanding the trade-off between food production and biodiversity conservation by comparing region-wide land use scenarios which are equivalent in terms of overall food production.

2. Here, for two contrasting regions of lowland England (The Fens and Salisbury Plain), we use empirical data and predictive models to compare a suite of spatially explicit scenarios reflecting the full range of the sharing-sparing continuum, including mixed scenarios which combine elements of both sharing and sparing. We evaluate a range of outcomes (bird populations, global warming potential (GWP), nitrogen and phosphorus pollution and outdoor recreation), in order to identify approaches to regional land use planning with the potential to deliver multiple societal benefits.

3. Land-sharing scenarios (which reduce the dominance of productive agricultural land in farmed areas and the area of larger unfarmed areas) result in negative outcomes, particularly for birds and GWP. In contrast, many land-sparing scenarios (including mixed scenarios which increase the area of lower-yield farmland alongside larger unfarmed areas) resulted in improvements in all or most outcomes, although for recreation and nutrient export differences between scenarios were modest.

4. Importantly, environmental outcomes also depended on the spatial arrangement of spared land, the types of natural or semi-natural habitat promoted on spared land, whether some lower-yield farmland is delivered alongside larger unfarmed areas, and the overall region-wide food production target.

5. Policy implications. Our study suggests that land-sparing strategies which increase the area of natural and seminatural areas can improve environmental outcomes, despite the costs associated with high-yield agriculture. However, high-yield agriculture should not compromise future production or ecosystem services on spared land, and explicit policies such as certification or payments for ecosystem services are required to link sustainable high-yield production to habitat conservation. Our study also highlights the importance of mitigating projected increases in food demand.

Methods
Modelled properties of each land use scenario. See associated manuscript for full description.

1. 探索如何合理配置土地以可持续实现多重相互竞争的目标，是一项重大的社会挑战。土地共享-保护框架（land sharing-sparing framework）提供了一种启发式方法：通过对比整体粮食产量相当的全区域土地利用情景，解析粮食生产与生物多样性保护之间的权衡关系。
2. 本研究以英格兰低地的两个典型区域——芬斯地区（The Fens）与索尔兹伯里平原（Salisbury Plain）为研究对象，利用实证数据与预测模型，对比一系列涵盖共享-保护连续体全谱系的空间显性情景，其中包括融合共享与保护要素的混合情景。本研究对多项结果指标（鸟类种群、全球增温潜势（GWP）、氮磷污染以及户外游憩效益）进行评估，旨在识别可同时实现多重社会收益的区域土地利用规划路径。
3. 土地共享情景（即降低耕作区内高产农田的占比，并缩减大型未耕作区域的面积）会带来负面效益，尤其对鸟类种群与全球增温潜势影响显著。与之形成对比的是，多数土地保护情景（包括在扩大大型未耕作区域的同时增加低产农田面积的混合情景）可使全部或大部分指标得到改善，不过不同情景间的户外游憩与养分输出差异相对有限。
4. 值得注意的是，环境效益还取决于保护用地的空间布局、保护用地内所营造的自然或半自然生境类型、是否在扩大大型未耕作区域的同时配套一定比例的低产农田，以及全区域整体的粮食生产目标。
5. 政策启示：本研究表明，尽管高产农业存在一定成本，但扩大自然与半自然用地面积的土地保护策略仍可改善环境效益。不过，高产农业不得损害保护用地的未来生产能力与生态系统服务功能，同时需要建立认证、生态系统服务付费等明确政策，将可持续高产生产与生境保护相结合。此外，本研究还强调了缓解预期粮食需求增长的重要性。

研究方法：各土地利用情景的模拟属性详见配套论文完整说明。