Bird conservation and the land sharing‐sparing continuum in farmland‐dominated landscapes of lowland England

Linnet. By John Harding.

Author(s): Finch, T., Gillings, S., Green, R.E., Massimino, D., Peach, W.J. & Balmford, A.

Published: March 2019  

Journal: Conservation Biology Volume: 33

Digital Identifier No. (DOI): 10.1111/cobi.13316

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Agriculture is necessary to meet the food demands of an increasing human population, but it is also a leading threat to biodiversity, both because natural habitats are destroyed when land is converted to agricultural use and because the intensive management of existing agricultural land has negative consequences for many species. For this reason, scientists are studying strategies to mitigate the impacts of agriculture on biodiversity.

One way of thinking about and testing the different options for land management is to consider ‘land sparing’ versus ‘land sharing’. Land sparing is a scenario where a significant amount of land is spared from agriculture. The advantage of land sparing is that natural habitats may be fully preserved in the spared areas, such as large nature reserves or rewilded landscapes. However, as the cultivated part of the landscape is smaller it must be managed very intensively to achieve high yields, with deleterious consequences for farmland biodiversity. On the other hand, land sharing integrates food production and biodiversity conservation on the same areas. An example of land sharing is our current approach using agri-environment schemes to ‘soften’ farmland so that food production and biodiversity can coexist in the same area. A key question is how well biodiversity can coexist in this way and whether sparing might benefit more species.

Research conducted in tropical areas suggests that land sparing is likely to protect more species compared to land sharing. However, little was known about which strategy could be the best suited for Britain and Europe, where the land has long been subjected to the impacts of agriculture. This knowledge gap has now been filled by a study led by RSPB, in collaboration with BTO and the University of Cambridge. Data collected by volunteers taking part in the Breeding Bird Survey were analysed to project how bird populations would change in The Fens and Salisbury Plain under a range of different food production strategies, involving land sparing, land sharing or mixed strategies.

This study showed that more species are likely to achieve bigger local populations under land sparing strategies compared to land sharing. This is not dissimilar to findings in tropical areas. However, some farmland species of global or national conservation interest, such as Lapwing or Corn Bunting, are projected to benefit from land sharing or intermediate strategies.

The study concluded that in areas dominated by farmland landscapes, such as lowland England, intermediate strategies between land sparing and land sharing may be the best. Three-compartment strategies, which involve maintaining natural areas fully spared from agriculture, low-yield farmland, and high-yield farmland, could potentially represent the best compromise between the needs of satisfying food demand and conserving biodiversity.

Abstract
Empirical evidence from many regions suggests that most species would be least negatively affected if human food demand were met through high‐yield agricultural production and conservation of nonfarm ecosystems (land sparing), rather than through wildlife‐friendly farming over a larger area (land sharing). However, repeated glaciation and a long history of agriculture may lead to different results in regions such as western Europe. We compared the consequences of land sparing and land sharing on breeding bird species in 2 lowland regions of England, The Fens, with 101 species, and Salisbury Plain, with 83. We derived density–yield responses for each species and then estimated regional population size under regional food production strategies, including land sharing and land sparing, a range of intermediate strategies, and a novel mixed strategy. In both regions, more species achieved maximum regional population size under land sparing than land sharing. In The Fens, the majority of birds were loser species (estimated to have smaller populations under all food production strategies than in the preagricultural baseline scenario), whereas in Salisbury Plain the majority were winners (smaller populations in the preagricultural baseline scenario). Loser species overwhelmingly achieved maximum regional population size under land sparing, whereas winner species achieved maximum regional population size under either land sharing or an intermediate strategy, highlighting the importance of defining which groups of species are the target of conservation. A novel 3‐compartment strategy (combining high‐yield farming, natural habitat, and low‐yield farming) often performed better than either land sharing or land sparing. Our results support intermediate or 3‐compartment land‐sparing strategies to maximize bird populations across lowland agricultural landscapes. To deliver conservation outcomes, any shift toward land sparing must, however, ensure yield increases are sustainable in the long term, do not entail increased negative effects on surrounding areas, and are linked to allocation of land for nature.
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