Estimating global land system impacts of timber plantations using MAgPIE 4.3.5

Abstract

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.

Land use change and carbon emissions of a transformation to timber cities

“…8). Investments in yield-increasing technological change (measured as Tau factor in MAgPIE 11,22 ) are similar across the scenarios, not only on an aggregated global scale but also on a regional scale (Supplementary Fig. 8).…”

“…13). The need for yield-increasing investments due to competition for land could also result in changes in agricultural land-use patterns due to geographical specialization in agricultural production 11 (Supplementary Fig. 13).…”

“…Forest-land dynamics are modeled via two separate but synergistic representations in MAgPIE (Forestry and Natural Vegetation) 11 . The forestry representation in MAgPIE defines highly managed plantations with age-class dynamics, afforestation, and above-ground carbon dynamics.…”

“…In the mid to long term, highly productive plantations could therefore increase wood production while alleviating harvest pressure from natural forests under strict biodiversity and land protection regimes 10 . Wood needed for future timber constructions can come from increasing forest harvest from managed forest plantations and natural forests, redirecting existing wood uses, or establishing new forest plantations (which can be harvested at maturity in the future but provide wood from intermediate thinning until then) 6,9,11 .…”

“…Currently, harvested wood is already used for other purposes and not necessarily available nor of adequate quality to be used as engineered wood. Furthermore, establishing new plantations has both land-use implications 11 (in terms of competition for land) and negative biodiversity impacts 15 when natural ecosystems are replaced. Therefore, the question of where to source the wood for the construction of timber cities is crucial.…”