Biofuels on the landscape: Is “land sharing” preferable to “land sparing”?

Abstract

Abstract. Widespread land use changes, and ensuing effects on ecosystem services, are expected from expanding bioenergy production. Although most U.S. production of ethanol is from corn, it is envisaged that future ethanol production will also draw from cellulosic sources such as perennial grasses. In selecting optimal bioenergy crops, there is debate as to whether it is preferable from an environmental standpoint to cultivate bioenergy crops with high ecosystem services (a ''land-sharing'' strategy) or to grow crops with lower ecosystem services but higher yield, thereby requiring less land to meet bioenergy demand (a ''land-sparing'' strategy). Here, we develop a simple model to address this question. Assuming that bioenergy crops are competing with uncultivated land, our model calculates land requirements to meet a given bioenergy demand intensity based upon the yields of bioenergy crops. The model combines fractional land cover of each ecosystem type with its associated ecosystem services to determine whether land-sharing or land-sparing strategies maximize ecosystem services at the landscape level. We apply this model to a case in which climate protection through GHG regulation-an ecosystem's greenhouse gas value (GHGV)-is the ecosystem service of interest. Our results show that the relative advantages of land sparing and land sharing depend upon the type of ecosystem displaced by the bioenergy crop; as the GHGV of the unfarmed land increases, the preferable strategy shifts from land sharing to land sparing. Although it may be preferable to replace ecologically degraded land with high-GHGV, lower yielding bioenergy crops, average landscape GHGV will most often be maximized through highyielding bioenergy crops that leave more land for uncultivated, high-GHGV ecosystems. Although our case study focuses on GHGV, the same principles will be applicable to any ecosystem service whose value does not depend upon the spatial configuration of the landscape. Whenever bioenergy crops have substantially lower ecosystem services than the ecosystems with which they are competing for land, the most effective strategy for meeting bioenergy demand while maximizing ecosystem services on a landscape level is one of land sparing: focusing simultaneously on maximizing the yield of bioenergy crops while preserving or restoring natural ecosystems.

Using satellite vegetation and compound topographic indices to map highly erodible cropland buffers for cellulosic biofuel crop developments in eastern Nebraska, USA

“…Because switchgrass is highly productive (and more productive when fertilizers and chemicals are applied to encourage its growth as a dense monoculture) and has higher biomass production than most grassland species, the total estimated switchgrass biomass productivity was assumed to be double that of the total estimated grassland biomass productivity based on previous study results ( Anderson-Teixeira et al, 2012;Behrman et al, 2012;Bonin and Lal, 2014;Fike et al, 2006;Jager et al, 2010;Kiniry et al, 2008;McLaughlin et al, 2006;Schmer et al, 2010;Tulbure et al, 2012;Vogel et al, 2002;Wullschleger et al, 2010).…”

Potential of global croplands and bioenergy crops for climate change mitigation through deployment for enhanced weathering

“…Lett. 13: 20160714 marginal land [11,57]. While 2G bioenergy crops have lower nutrient requirements than 1G crops ( perennial grasses in the USA range from unfertilized to half the rate of maize) [12], plant-induced weathering of basalt could supply nutrients that improve marginal soils, increasing yields and promoting further organic C sequestration.…”

“…In addition, growing interest in biofuels to reduce fossil fuel consumption has increased the proportion of agricultural land producing annual and perennial bioenergy crops, with the potential to expand into marginal lands [7,[11][12][13]. Perennial crops have longer growing seasons than annuals and extensive root systems supporting large biotic communities [8,11,14], which may be more effective than annuals at weathering. In this review, we examine the potential for basalt EW to sequester CO 2 and benefit crop yield in conventional and perennial bioenergy agroecosystems.…”

Shaping the multifunctional tree: the use of Salicaceae in environmental restoration

“…In choosing the optimal strategy for multifunctional tree plantations, it may be preferable to grow specialized tree crops with high yield, as the greenhouse gas value increases, leaving more land to the recolonization of native woody species (cf. Anderson-Teixeira et al 2012), including poplar-willow alluvial stands. Alternatively, multifunctional tree plantations with high ecosystem service may be widely cultivated or restored for the replacement of ecologically degraded functions (e.g., biodiversity conservation), intentionally sacrificing maximum yield.…”