DOI: 10.5061/dryad.69p8cz8xs
title: Optimising nature conservation outcomes for a given region-wide level of food production

description: The land sharing-sparing framework aims to quantify the trade-off between
 food production and biodiversity conservation, but it has been criticised
 for offering, for reasons of simplicity, an unrealistically limited set of
 different land uses. Here, we develop the framework to evaluate a much
 larger suite of land-use strategies in which the areas and yields of three
 land-use compartments, natural habitat, high-yield farmland, and
 lower-yield farmland, are varied simultaneously. For two regions of
 England, we use functions that relate the local population density of
 breeding bird species to farm yield to simulate species-specific
 region-wide population sizes under each strategy. We find that geometric
 mean population size, averaged across all species, is maximised when
 farmland yields are higher than the current average yield, and when spared
 land combines both natural habitat and low-yield farmland. This conclusion
 is relatively insensitive to the maximum yield considered feasible under
 extreme land sparing, and holds across a range of region-wide food
 production targets.  To some extent, our conclusion depends on
 which species groups were included in the assessment. Considered alone,
 farmland birds preferred a strategy with little or no natural habitat.
 Nonetheless, the optimal strategy was broadly consistent across all
 widely-recognised listings of species of conservation concern. Synthesis
 and applications. Our study looks at landscapes with a long history of
 agricultural use, and which have little remaining natural habitat, such as
 those found in lowland England. In these landscapes, conservation outcomes
 are likely to be maximised by mixed strategies in which high-yield
 production enables an increase in area of both natural habitat and
 low-yield farmland elsewhere in the region. 
description: We have provided annotated R script
 (optimal_strategy_script.R) along with 7 input
 files. This code creates scenarios and calculates
 geometric mean population size, allowing all figures (1-5) to be
 reproduced.   <strong>Input
 file 1: </strong>current.csv
 Current (2015) properties of each 1-km square in each
 region <em>gridref </em>Unique identifier
 for each 1-km square <em>nca </em>National
 Character Area (either The Fens or Salisbury Plain)
 <em>habitat </em>Either farmed, or wet grassland or
 fen in The Fens or chalk grassland or woodland in Salisbury
 Plain 
 <em>unbuilt </em>Proportion of square which is not urban or suburban <em>currency </em>Yield currency (energy) <em>yield </em>Yield of unbuilt land (GJ per ha) <em>production </em>Production from all land (yield * unbuilt)   <strong>Input file 2: </strong>spared.csv Average properties of spared land <em>habitat </em>wet grassland or fen in The Fens or chalk grassland or woodland in Salisbury Plain currency Yield currency (energy) unbuilt Total area which is not urban or suburban <em>yield </em>Average yield (GJ per ha) <em>production </em>Average production (yield) <em>nca </em>National Character Area (either The Fens or Salisbury Plain)   <strong>Input file 3: </strong>dy_pars.csv Density-yield parameters <em>currency </em>Yield currency (energy) <em>spp </em>2-letter species code <em>english </em>Species name <em>max.density </em>Maximum observed density <em>mean.density </em>Mean observed density <em>max.yield </em>Maximum yield across survey sites <em>upwards </em>TRUE if density-yield curve trends upwards at <em>max.yield</em>, otherwise FALSE <em>mod </em>A if 3-parameter model, B if 4-parameter model <em>b0 </em>Density-yield parameter (see equations 1 and 2 in Finch et al. (2019) DOI: 10.1111/cobi.13316) <em>b1 </em>Density-yield parameter (see equations 1 and 2 in Finch et al. (2019) DOI: 10.1111/cobi.13316) <em>b2 </em>Density-yield parameter (see equations 1 and 2 in Finch et al. (2019) DOI: 10.1111/cobi.13316) <em>alpha </em>Density-yield parameter (see equations 1 and 2 in Finch et al. (2019) DOI: 10.1111/cobi.13316) <em>top </em>Top model (A or B) <em>nca </em>National Character Area (either The Fens or Salisbury Plain)   <strong>Input file 4: </strong>traits.csv Species traits (each species appears in multiple rows, according to group identity) <em>spp </em>2-letter species code <em>english </em>Species name <em>nca </em>National Character Area (either The Fens or Salisbury Plain) <em>group </em>Group - see main text.    <strong>Input file 5: </strong>wg_fens.csv Density in wet grassland (for The Fens only) <em>spp </em>2-letter species code <em>english </em>Species name <em>habitat </em>wet grassland <em>density </em>Average density   <strong>Input file 6: </strong>wd_sali.csv Density in woodland (for Salisbury Plain only) <em>spp </em>2-letter species code <em>english </em>Species name <em>habitat </em>woodland <em>density </em>Average density   <strong>Input file 7: </strong>fenwg_fens.csv Additional natural habitat specialists (for The Fens only) <em>spp </em>2-letter species code <em>english </em>Species name <em>habitat </em>fen or wet grassland <em>density </em>Relative density 1 (present) or 0 (absent)