In the transition to a more sustainable land future, our land footprint will, among many land-use change drivers, mainly depend on the interplay of population growth, agricultural efficiency, land-use regulation and consumption changes. In a new study published in Nature Communications by an international research group from PBL, IIASA, PIK, PNNL, WECR, IFPRI and NIES, a comparison of several often-used assessment models and scenarios shows that a combination of these factors can help limit human pressure on land while safeguarding food security.
Land-use plays a key role in sustainable development, and the recent international assessments by IPBES, UNEP and IPCC make intensive use of model-based land-use projections, built around standardized set of scenarios, the Shared Socioeconomic Pathways (SSPs). In this study, the modelling groups involved in the quantification of these scenarios worked at better disentangling the key determinants of global land-use projections. The researchers use systematic sensitivity experiments to explain spread in models and scenarios, and identify the main factors determining the transition to a more sustainable (or unsustainable) land future. Going beyond qualitative relations, they identify the relative contribution of these factors and illustrate how the combination of land-use regulation, agricultural productivity and dietary change can help achieving the transition of land use as part of the sustainable development goals.
Sensitivity experiments explain model spread and identify policy leverages
The recently developed sensitivity approach allows to identify how land-use in the SSP scenarios depends on six distinct socio-economic drivers, namely population, wealth, consumption preferences, agricultural productivity, land-use regulation and trade, and their interactions. By isolating the response to each of these factors, the authors find that model spread is arising from diverging model sensitivities, but also from diverging assumptions and representations of how these drivers will evolve in the future, especially in land-use regulation and trade, calling for reconciliation efforts and more empirical research.
Furthermore, the sensitivity experiments allow identification of the key determinants and their relative importance in achieving a sustainable land-use future, and what needs to be avoided in order to avoid situations where land expansion would put primary forests and other natural ecosystems at risk.
Key factors in the transition to a sustainable land system
The key determinants for future land use identified in this study (population, agricultural efficiency, land-use regulation and dietary changes) are consistent with earlier publications. However, the present study also emphasizes the role of population growth, often overlooked in recent studies about biodiversity protection, climate mitigation, and sustainable development. Although controversial, results here indicate that limiting population growth can be effective in achieving a sustainable land and food system, together with the other key drivers of the land use system. First, increasing agricultural productivity decreases the amount of land needed to feed each individual. Second, enforcing more efficient land use protection for forest and other biodiverse natural habitats mitigates the most adverse impacts of expansion of agricultural land. Finally, shifting diets towards less resource intensive products, in particular with lower share of livestock products, can also alleviate the human pressure on the ecosystems and the demand for land.
Combining land saving options for a more sustainable future
This systematic multi-model analysis also adds one additional level of understanding on how the different options above interact, and how to best combine them. For instance, an increase in agricultural efficiency can reduce demand for cropland, but at the same time also boost production and trigger higher consumption levels due to lower prices. Yield increase is therefore shown to be more effective in reducing land use when combined with land-use regulation and consumption changes. Similarly, land-use regulation can decrease expansion into cropland but may create a risk for food security, if not bundled with increased productivity and consumption shifts.