Biogeophysical and biogeochemical impacts of land-use change simulated by MIROC-ES2L

Akihiko Ito,Tomohiro Hajima

doi:10.1186/s40645-020-00372-w

Abstract

Land-use change is one of the focal processes in Earth system models because it has strong impacts on terrestrial biogeophysical and biogeochemical conditions. However, modeling land-use impacts is still challenging because of model complexity and uncertainty. This study examined the results of simulations of land-use change impacts by the Model for Interdisciplinary Research on Climate, Earth System version 2 for long-term simulations (MIROC-ES2L) conducted under the Land-Use Model Intercomparison Project protocol. In a historical experiment, the model reproduced biogeophysical impacts such as decreasing trends in land-surface net radiation and evapotranspiration by about 1970. Among biogeochemical impacts, the model captured the global decrease of vegetation and soil carbon stocks caused by extensive deforestation. By releasing ecosystem carbon stock to the atmosphere, land-use change shortened the mean residence time of terrestrial carbon and accelerated its turnover rate, especially in low latitudes. Future projections based on Shared Socioeconomic Pathways indicated substantial alteration of land conditions caused primarily by climatic change and secondarily by land-use change. Sensitivity experiments conducted by exchanging land-use data between different future projection baseline experiments showed that, at the global scale, the anticipated extent of land-use conversion would likely play a modest role in the future terrestrial radiation, water, and carbon budgets. Regional investigations revealed that future land use would exert a considerable influence on runoff and vegetation carbon stock. Further model refinement is required to improve its capability to analyze its complicated terrestrial linkages or nexus (e.g., food, bioenergy, and carbon sequestration) to climate-change impacts.

Highlights

Land-use change associated with the human population and economic growth is a critical driver of global change (Houghton 1994; Foley et al 2005)
We first briefly describe the land-use scheme in the MIROC-ES2L, and we present preliminary results of simulations of land-use impacts conducted under the Land-Use Model Intercomparison Project (LUMIP) protocol
We focused on the biogeochemical variables net primary production, leaf area index, vegetation carbon stock, and soil carbon stock

Summary

Introduction

Land-use change (e.g., expansion of cropland at the cost of primary forest) associated with the human population and economic growth is a critical driver of global change (Houghton 1994; Foley et al 2005). Land-use change encompasses various human activities such as harvesting trees for fuel wood, shifting cultivation, pasturing of livestock, and selective logging. As a result of long-term land use, most natural vegetation has been influenced by human activities, with the exception of limited reserved land areas (Pongratz et al 2009; Kaplan et al 2010). Drastic land cover changes have an immediate impact on surface biophysical characteristics such as albedo and roughness (Henderson-Sellers et al 1993), which greatly affect the net radiative and hydrological budgets at the land surface and subsequent propagation of these effects leads to impacts on local to global atmospheric dynamics (Sud et al 1996; Takata et al 2009).

Methods

Results

Conclusion