Land sparing to make space for species dependent on natural habitats and high nature value farmland.

Empirical evidence from four continents indicates that human food demand may be best reconciled with biodiversity conservation through sparing natural habitats by boosting agricultural yields. This runs counter to the conservation paradigm of wildlife-friendly farming, which is influential in Europe, where many species are dependent on low-yielding high nature value farmland threatened by both intensification and abandonment. In the first multi-taxon population-level test of land-sparing theory in Europe, we quantified how population densities of 175 bird and sedge species varied with farm yield across 26 squares (each with an area of 1 km2) in eastern Poland. We discovered that, as in previous studies elsewhere, simple land sparing, with only natural habitats on spared land, markedly out-performed land sharing in its effect on region-wide projected population sizes. However, a novel 'three-compartment' land-sparing approach, in which about one-third of spared land is assigned to very low-yield agriculture and the remainder to natural habitats, resulted in least-reduced projected future populations for more species. Implementing the three-compartment model would require significant reorganization of current subsidy regimes, but would mean high-yield farming could release sufficient land for species dependent on both natural and high nature value farmland to persist.

Carbon Storage and Land-Use Strategies in Agricultural Landscapes across Three Continents.

The loss of carbon stocks through agricultural land-use change is a key driver of greenhouse gas emissions [1-4], and the methods used to manage agricultural land will have major impacts on the global climate in the 21st century [4-9]. It remains unresolved whether carbon losses would be minimized by increasing farm yields and limiting the conversion of natural habitats ("land sparing"), or maximizing on-farm carbon stocks, even at the cost of reduced yields and therefore greater habitat clearance ("land sharing"). In this paper, we use field surveys of over 11,000 trees, in-depth interviews with farmers, and existing agricultural data, to evaluate the potential impacts of these contrasting approaches, and plausible intermediate strategies, on above-ground carbon stocks across a diverse range of agricultural and natural systems. Our analyses include agroforestry and oil palm plantations in the humid tropics of Ghana; cattle ranching in dry tropical forest in Mexico; and arable cropping in temperate wetlands and forests in Poland. Strikingly, despite the range of systems investigated, land sparing consistently had a higher potential to sustain regional above-ground carbon stocks than any other strategy. This was the case in all three regions and at all plausible levels of food production, including falls in demand. However, if agricultural production increases to meet likely future demand levels, we project large decreases in above-ground carbon stocks, regardless of land-use strategy. Our results strongly suggest that maintaining above-ground carbon stocks will depend on both limiting future food demand and minimizing agricultural expansion through linking high-yield farming with conserving or restoring natural habitats.