The global human population is estimated to grow to 9 billion by 2050. Not only will there be more mouths to feed, but increasingly wealthy societies will demand a more protein-rich diet, which will require considerable land and investment. With much of the world’s productive land already under some sort of cultivation, policy makers are struggling to reconcile the need to grow additional food with the need to avoid encroaching on already threatened ecosystems.

Some advocate a process of “land sharing”, whereby agricultural production takes place within complex multi-functional landscapes. Others favour “land sparing”, where agricultural production on already cultivated or marginal lands is maximised, so that other areas are set aside for the conservation of biodiversity.

Although the “land sparing” versus “land sharing” debate presents itself as a black or white choice (as in this article, for example: http://news.mongabay.com/2011/0901-hance_landsaving.html), there are in fact many shades of grey in land-use planning, dependent on a multitude of interacting factors: be they geographical, ecological, economic, social and political. Surprisingly, there are few comprehensive studies that provide real-life examples of the potential for land sparing or land sharing for agriculture and associated biodiversity benefits.

It is timely then that Victor Gutíerrez-Vélez and colleagues have recently published research on differing systems of oil palm expansion in the Peruvian Amazon and its impacts on forest conversion. Using remote sensing techniques, supported by on-the-ground research, Gutíerrez-Vélez et al. were able to differentiate between industrial-scale, high-yielding oil palm expansion and smallholder, low-yield cropping systems and how these two different systems were integrated into current land uses. Their findings are somewhat surprising.

Gutíerrez-Vélez and his colleagues found that, although low-yield smallholder plantations accounted for the largest overall expansion of oil palm (80%), only 30% of this resulted in direct forest conversion. However, the high-yield expansion, although minimising the total area to achieve production targets, resulted in a 75% increase in the conversion of old-growth forests. Clearly for those advocating land sparing as a means to achieve agricultural production and biodiversity conservation, this goes against perceived wisdom.

So, why did high yielding production of oil palm result in increased forest loss? Gutíerrez-Vélez et al. speculate that expansion is closely related to tenure. Land previously cleared, which would be the most appropriate for high-yield agriculture, is often subject to uncertain ownership and hence tenure is often disputed. For many commercial concerns, it is easier to acquire forested land owned by the State, thus avoiding the social and political complications of potential land disputes. Conversely, most smallholder oil palm expansion took place in areas that were cleared previously, where, as the demand for land is small, tenure rights are easier to negotiate.

An added complication reported by Gutíerrez-Vélez et al. is the favourable economic environment currently in place in Peru for commercial agriculture, such as political support, tax breaks and subsidies, which provide considerable incentives for conversion of old-growth forests. Providing similar incentives to encourage such expansion into marginal lands or into areas already cleared would have a significant effect on current rates of land conversion, conclude Gutíerrez-Vélez and his colleagues. Although Peru is not currently a major oil palm producer, the current incentives in place to increase production will probably result in the conversion of yet more old-growth forest: a worrying trend in much of the tropics.

Gutíerrez-Vélez et al. illustrate the wider social and political complexities behind such seemingly simple concepts as “land sparing” and “land sharing”. Clearly we have a long way to go in reconciling agricultural production for an ever-growing population while preserving our ever-diminishing natural resources.