Abstract. Out of 1150 Mha (million hectares) of forest designated primarily for production purposes in 2020, plantations accounted for 11 % (131 Mha) of this area
and fulfilled more than 33 % of the global industrial roundwood demand. However, adding additional timber plantations to meet increasing timber
demand intensifies competition for scarce land resources between different land uses such as food, feed, livestock and timber production. Despite the
significance of plantations with respect to roundwood production, their importance in meeting the long-term timber demand and the implications of plantation
expansion for overall land-use dynamics have not been studied in detail, in particular regarding the competition for land between agriculture and
forestry in existing land-use models. This paper describes the extension of the modular, open-source land system Model of Agricultural Production and its Impact on the Environment
(MAgPIE) using a detailed representation of forest land, timber production and timber demand dynamics. These extensions allow for a better understanding of the
land-use dynamics (including competition for land) and the associated land-use change emissions of timber production. We show that the spatial cropland patterns differ when timber production is accounted for, indicating that timber plantations compete with cropland
for the same scarce land resources. When plantations are established on cropland, it causes cropland expansion and deforestation elsewhere. Using the
exogenous extrapolation of historical roundwood production from plantations, future timber demand and plantation rotation lengths, we model the
future spatial expansion of forest plantations. As a result of increasing timber demand, we show a 177 % increase in plantation area by
the end of the century (+171 Mha in 1995–2100). We also observe (in our model results) that the increasing demand for timber amplifies the
scarcity of land, which is indicated by shifting agricultural land-use patterns and increasing yields from cropland compared with a case without
forestry. Through the inclusion of new forest plantation and natural forest dynamics, our estimates of land-related CO2 emissions better match with observed data, in particular the gross land-use change emissions and carbon uptake (via regrowth), reflecting higher deforestation with
the expansion of managed land and timber production as well as higher regrowth in natural forests and plantations.
The expansion of large-scale tree plantations:
Detection, pathways, and development trade-offs