Implementation of the land-sharing and land-sparing framework in agro-ecological corridors

Abstract

Maintaining adequate food supply while conserving biodiversity is one of the great challenges in conservation today. There is a fundamental controversy between land sparing and land sharing[1]: Land sparing favors intensive agriculture that allows maximal food production in a small area and spares land for conservation, while land sharing favors agro-environmental practices that create multifunctional agroecosystems. While land sparing has proven more advantageous in intact forests, evidence from long-history agricultural landscapes is mixed[2]. Using the sparing-sharing framework, we assessed costs and benefits of agriculture and conservation in planning an ecological corridor in the Jezreel Valley, Israel.

We compared land sharing - using environmentally-friendly practices to create a corridor (100 km2) -- with land sparing of wide, intact natural patches (50-300m). To assess these two alternatives, we surveyed biodiversity of five taxonomic groups throughout the agricultural season in six common crops, across two land-sharing practices (uncultivated field-margins and reduced-tillage), and large, spared natural patches. Then we assessed the economic costs (profit and revenue) of these alternatives. Results indicate that uncultivated field-margins are highly biodiverse, despite suffering from a high level of disturbance. Surprisingly, arthropods (ground-dwelling arthropods, butterflies and parasitic wasps) show higher or similar diversity in field-margins as compared to natural patches. This pattern is not consistent with diversity of plants and birds, which is higher in natural patches. Composition analysis shows unique communities in field-margins and higher species turnover for arthropods, emphasizing field-margins contribution at large-scales. Unlike field-margins, reduced-tillage did not affect biodiversity. Economically, field-margins are correlated with higher revenue of some crops, which could be attributed to the pest-control services they provide.

Our results indicate that in long-history agricultural landscapes, sparing is better than sharing in creating ecological corridors, but the optimal strategy is a combination of both. Thus, wide, natural patches should be the foundation of the agro-ecological corridor because they support the greatest biodiversity. In addition, field-margins make a better land-sharing strategy than reduced tillage; we found that reduced tillage did not affect biodiversity, regardless of its benefit in reducing soil erosion. The addition of field-margins further improves biodiversity, increasing habitat diversity in the landscape, and enhancing pest-control services that provide economic benefit to farmers.

[1] Phalan et al. 2011. Reconciling food production and biodiversity conservation: land sharing and land sparing compared. Science.

[2] von Wehrden et al. 2014. Realigning the land-sharing/land-sparing debate to match conservation needs: Considering diversity scales and land-use history. Landscape Ecol.