The Nexus Land-Use model version 1.0, an approach articulating biophysical potentials and economic dynamics to model competition for land-use

Abstract

Interactions between food demand, biomass energy and forest preservation are driving both food prices and land-use changes, regionally and globally. This study presents a new model called Nexus Land-Use version 1.0 which describes these interactions through a generic representation of agricultural intensification mechanisms. The Nexus Land-Use model equations combine biophysics and economics into a single coherent framework to calculate crop yields, food prices, and resulting pasture and cropland areas within 12 regions inter-connected with each other by international trade. The representation of cropland and livestock production systems in each region relies on three components: (i) a biomass production function derived from the crop yield response function to inputs such as industrial fertilisers; (ii) a detailed representation of the livestock production system subdivided into an intensive and an extensive component, and (iii) a spatially explicit distribution of potential (maximal) crop yields prescribed from the Lund-Postdam-Jena global vegetation model for managed Land (LPJmL). The economic principles governing decisions about land-use and intensification are adapted from the Ricardian rent theory, assuming cost minimisation for farmers. The land-use modelling approach described in this paper entails several advantages. Firstly, it makes it possible to explore interactions among different types of biomass demand for food and animal feed, in a consistent approach, including indirect effects on land-use change resulting from international trade. Secondly, yield variations induced by the possible expansion of croplands on less suitable marginal lands are modelled by using regional land area distributions of potential yields, and a calculated boundary between intensive and extensive production. The model equations and parameter values are first described in details. Then, idealised scenarios exploring the impact of forest preservation policies or rising energy price on agricultural intensification are described, and their impacts on pasture and cropland areas are investigated

The greenhouse gas balance of European grasslands

“…Not all pasture is intensively managed. Livestock production involves a variety of cultivation practices and management strategies, which can be classified as intensive or extensive management (Souty et al, 2012). Farmers can graze their animals in fields, harvest grass for forage production, grow fodder crops or buy complementary feed products.…”

Global change effects on land management in the Mediterranean region

“…Significant improvements in the modelling of future land use have been made in the recent decades, including more precise coverage of spatial, temporal and thematic resolution and moving beyond an approach based only on dominant land cover (Hurtt et al, 2011;Letourneau et al, 2012;Souty et al, 2012;Bryan et al, 2016). Land management which used to be represented in a simplified manner as a class of regional management factor (Bouwman et al, 2006;Bondeau et al, 2007), can now be described using different management intensity metrics, such as livestock numbers, fertilizer inputs or yield gaps (Souty et al, 2012;van Asselen & Verburg, 2013). This is necessary, as often socio-economic changes are not limited to direct land cover changes, but predominantly lead to changes in management intensity or irrigation.…”

The Impact of Globalization on Food and Agriculture: The Case of the Diet Convergence

“…Given the assumption of a full convergence of every region towards the US food habits in 2050, the growth in food availability in the USConv scenario is very high (+45% over , especially for ruminant (+163%) and monogastric calories (+141%). To explore the impacts of these four diet scenarios on agriculture and land-use, we use the Nexus Land-Use model (NLU), which simulates changes in the agricultural sector at the global level under various assumptions regarding biomass demand (Souty et al, 2012). Food markets are not represented in this study, as we test exogenous pathways of dietary change.…”

“…Then, we test the impact on agriculture of each of these food foresights. To test these scenarios, we use them, with two additional contrasting scenarios of diet convergence, as exogenous inputs in the global model of land-use and agricultural intensification Nexus Land-Use (NLU) (Souty et al, 2012). This model is particularly suited to this study as it distinguishes between plant food, ruminant and monogastric calories, and associates them to a specific production process.…”