EDITOR'S CHOICE: Surrounding habitats mediate the trade‐off between land‐sharing and land‐sparing agriculture in the tropics

Abstract

Summary1. Two strategies are often promoted to mitigate the effects of agricultural expansion on biodiversity: one integrates wildlife-friendly habitats within farmland (land sharing), and the other intensifies farming to allow the offset of natural reserves (land sparing). Their relative merits for biodiversity protection have been subject to much debate, but no previous study has examined whether trade-offs between the two strategies depend on the proximity of farmed areas to large tracts of natural habitat. 2. We sampled birds and dung beetles across contiguous forests and agricultural landscapes (low-intensity cattle farming) in a threatened hotspot of endemism: the Colombian Choc oAndes. We test the hypothesis that the relative biodiversity benefits of either strategy depend partially on the degree to which farmlands are isolated from large contiguous blocks of forest. 3. We show that distance from forest mediates the occurrence of many species within farmland. For the majority of species, occurrence on farmland depends on both isolation from forest and the proportionate cover of small-scale wildlife-friendly habitats within the farm landscape, with both variables having a similar overall magnitude of effect on occurrence probabilities. 4. Simulations suggest that the biodiversity benefits of land sharing decline significantly with increasing distance from forest, but land sparing benefits remain consistent. In farm management units situated close to large contiguous forest (<500 m), land sharing is predicted to provide equal benefits to land sparing, but land sparing becomes increasingly superior in management units situated further from forest (1500 m). The predicted biodiversity benefits of land sparing are similar across all distances, provided that sparing mechanisms genuinely deliver protection for contiguous forest tracts. 5. Synthesis and applications. The persistence of bird and dung beetle communities in lowintensity pastoral agriculture is strongly linked to the proximity of surrounding contiguous forests. Land-sharing policies that promote the integration of small-scale wildlife-friendly habitats might be of limited benefit without simultaneous measures to protect larger blocks of natural habitat, which could be achieved via land-sparing practices. Policymakers should carefully consider the extent and distribution of remaining contiguous natural habitats when designing agri-environment schemes in the tropics.

Source-Sink Dynamics: a Neglected Problem for Landscape-Scale Biodiversity Conservation in the Tropics

“…This is surprising, given that agricultural intensification and expansion are occurring more rapidly in the tropics than anywhere else [28], and are among the most prominent drivers of biodiversity loss in those regions [28,35,36]. Much research has examined the biodiversity value of agricultural landscapes in the tropics, particularly low-intensity agroecosystems that often support surprisingly diverse communities [37,38], and many studies have considered the potential for landscape-scale dispersal and 'spill-over effects' influence community composition in farmed areas [38 and refs therein]. However, our review suggests that relatively few studies have directly examined the spatial demography of populations inhabiting tropical agricultural landscapes, resulting in a paucity of studies reporting source-sink phenomena.…”

“…For example, in cattle farming systems in the Colombian Andes, many bird and dung beetle species can persist in 'wildlife-friendly' low-intensity farmland, but their abundances decline rapidly with distance from contiguous forest edges [38,64]. This suggests that low-intensity farmland may be a sink for these species, and that land-sparing may consequently be the optimal strategy for conservation, both for species richness and phylogenetic diversity [64,66].…”

What Have We Learned from the Land Sparing-sharing Model?

“…The original formulation of the land sparing-sharing framework omits some complexities, but it can be and already has been modified to incorporate many of these, including spatial configuration and the influence of edge effects [60,61]; the influence of changing diets and reducing food waste [50]; inclusion of some ecosystem services [4,7,50,62]; prediction of the effects of specific public policies [63]; and application to forestry [64,65], urban planning [66][67][68][69] and marine conservation [70]. It is a model, and so all assumptions can be varied and tested.…”

The intersection of food security and biodiversity conservation: a review

“…Regarding food security, the main focus was on the availability of food (all papers) and the ecological appropriateness of food production (16 papers). This cluster had the strongest link to (non-crop related) biodiversity assessment of any of the clusters in the analysis (e.g., Dutta and Jhala 2014; Gilroy et al 2014). However, papers in this cluster often lacked a precise definition of the conservation concerns or empirical measurement of biodiversity.…”

“…A unifying factor for papers in this cluster was a ''systematic'' approach to the food security-biodiversity conservation nexus addressing a range of both social and biophysical issues. This included different analytical frameworks, including ecosystems services (e.g., Ango et al 2014;Ju et al 2013), land sharing-land sparing (e.g., Gilroy et al 2014;Habel et al 2013), or general systems thinking (e.g., Fischer et al 2014). There was a strong focus on spatial scales, with all papers in the cluster addressing this issue.…”