Economic and not ecological variables shape the sparing-sharing trade-off in a mixed cropping landscape

1. The framework of land sparing vs. land sharing provides a useful
analytical tool to address the crop-production/biodiversity trade-off.
Despite multiple case-studies testing the sparing-sharing trade-off, this
framework still lacks the ability to identify the conditions in which
sparing, or sharing, would be the preferred strategy for pareto-optimizing
both food-production and biodiversity. Under some conditions, ecosystem
services may create a positive feedback between biodiversity and crop
production, affecting the optimization. 2. This study aims to identify the
conditions and the relevant variables that determine the preferred
land-use strategy in terms of maximizing both biodiversity and food
production, while accounting for positive feedback of ecosystem services
in this analysis. We used a simulation model with data from a mixed
cropping landscape (100 km2) covering seven crop types, five taxonomic
groups, three biodiversity metrics and 23 bioindicators to explore the
variables shaping the biodiversity-production trade-off and ecosystem
services underlying it. We explored a continuum of sparing large
semi-natural patches to sharing by maintaining uncultivated field margins
of varying size. 3. Land sparing outperformed land sharing in 62% of the
scenarios and it was economically more predictable. The optimization was
shaped by costs, associated with crop type, rather than by landscape
composition and configuration, biodiversity metric, taxonomic group or
bioindicator. 4. Landscape configuration and taxonomic group results
corroborate the notion that land sharing benefits mainly small organisms,
and that the common width of field-margins in many agri-environmental
policies (10 m) is not cost-effective compared to land sparing. 5. Land
sharing was the optimal strategy whenever it resulted in minimal costs,
despite contributing little to biodiversity. Yet, when field margins were
>20 m wide (small-scale sparing), land sharing maintained higher
biodiversity and was at least as cost-effective as sparing. 6. Synthesis
and applications. Our model highlights the importance of socio-economic
variables compared to ecological variables in selecting land-management
strategy to pareto-optimize both food production and biodiversity.
Considering opportunity costs alongside economic benefits from ecosystem
services in various cropping systems may therefore improve the
cost-effectiveness of biodiversity conservation policies in agricultural
landscapes.