Editor's Choice: Land-sparing and land-sharing in context

October 2014 (Issue 51:5)

Gilroy, J. J., Edwards, F. A., Medina Uribe, C. A., Haugaasen, T., Edwards, D. P. (2014), Surrounding habitats mediate the trade-off between land-sharing and land-sparing agriculture in the tropics. Journal of Applied Ecology. doi: 10.1111/1365-2664.12284

One of the most fundamental challenges for the conservation of biodiversity is balancing food production with outcomes for biodiversity. With the global population set to approach 10 billion people by 2050 (United Nations 2014), increasing demand for agricultural lands makes this an increasingly challenging prospect. This has generated considerable debate about how to maximise biodiversity while meeting needs for agricultural production. The predominant argument has been one that contrasts outcomes for biodiversity and agricultural production under scenarios of land-sparing versus land-sharing (Green et al. 2005; Fischer et al. 2014). Under a land-sparing scenario land is set aside for biodiversity separately from agricultural lands, whereas under a land-sharing scenario, agriculture production is less intensive and some biodiversity is maintained on agricultural lands.

Much of the science informing the land-sharing/land-sparing debate has focussed on analysing the trade-offs between biodiversity and agricultural production across the land-sparing/land-sharing continuum. The best choice of strategy depends critically on these trade-offs (Phalan et al. 2011), but the trade-offs can be highly context and scale dependent, limiting the extent to which generalisations can be made. One such context-dependency that has received little attention is the spatial context within which agricultural lands are placed, and in particular, the proximity to intact habitat for biodiversity.

In this issue Gilroy et al. (2014) tackle this question about the role of spatial context in driving trade-offs between biodiversity and agricultural production in the land-sharing versus land-sparing debate. To address this they focus on birds and dung beetles in the Colombian Chocó-Andes region; an area where agriculture is dominated by cattle farming. They first establish that the occurrence of birds and beetles in farmland depends on distance to forest (as well as the amount of wildlife friendly land cover on farmland) and quantify these relationships statistically. Then, using simulations, they examine to what extent the distance to intact forest mediates the performance of land-sparing versus land-sharing strategies. Their key message is that, for given levels of agricultural production, land-sharing performs increasingly less-well relative to land-sparing as the distance to intact forest increases. So the context within which agricultural lands sit, in terms of their proximity to intact habitat for biodiversity, is a crucial driver of the nature of trade-offs between biodiversity and agricultural production.

Apart from the important insights into the land-sparing/land-sparing debate, a particularly neat aspect of Gilroy et al. (2014) is the way they combine empirical data with simulations to explore the implications for planning and policy. They achieved this by first using state-of-the-art statistical models of ecological communities (Dorazio & Royle 2005; Dorazio et al. 2006) to provide robust estimates of the effects of the amount of wildlife-friendly land cover and the distance to intact forest. These models then provide predictions of the responses of biodiversity in the simulations. The explicit link between the empirical models and policy simulations provides a powerful approach for analysing the implications of ecological understanding for policy.

Asking questions about the role of isolation from large intact blocks of habitat has a long history in ecology, particularly in the area of island biogeography (MacArthur & Wilson 1967; Vellend 2003). However, Gilroy et al. (2014) are the first to apply this idea to understanding the relative benefits of land-sparing versus land-sharing. It doesn’t completely resolve the debate, but goes a long way towards resolving a significant part of the puzzle.

Jonathan Rhodes
Assistant Editor
j.rhodes@uq.edu.au

References

Dorazio, R.M. & Royle, J.A. (2005) Estimating size and composition of biological communities by modeling the occurrence of species. Journal of the American Statistical Association, 100, 389-398.
Dorazio, R.M., Royle, J.A., Söderström, B. & Glimskär, A. (2006) Estimating species richness and accumulation by modeling species occurrence and detectability. Ecology, 87, 842-854.
Fischer, J., Abson, D.J., Butsic, V., Chappell, M.J., Ekroos, J., Hanspach, J., Kuemmerle, T., Smith, H.G. & von Wehrden, H. (2014) Land sparing versus land sharing: moving forward. Conservation Letters, 7, 149-157.
Gilroy, J.J., Edwards, F.A., Medina Uribe, C.A., Haugaasen, T. & Edwards, D.P. (2014) Surrounding habitats mediate the trade-off between land-sharing and land-sparing agriculture in the tropics. Journal of Applied Ecology. doi: 10.1111/1365-2664.12284
Green, R.E., Cornell, S.J., Scharlemann, J.P.W. & Balmford, A. (2005) Farming and the fate of wild nature. Science, 307, 550-555.
MacArthur, R.H. & Wilson, E.O. (1967) The Theory of Island Biogeography. Princeton University Press, Princeton, USA.
Phalan, B., Onial, M., Balmford, A. & Green, R.E. (2011) Reconciling food production and biodiversity conservation: Land sharing and land sparing compared. Science, 333, 1289-1291.
United Nations (2014) The World Population Situation in 2014. A Concise Report. United Nations, New York, USA.
Vellend, M. (2003) Island biogeography of genes and species. American Naturalist, 162, 358-365.

 

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