A global assessment of gross and net land change dynamics for current conditions and future scenarios

Abstract

Abstract. The consideration of gross land changes, meaning all area gains and losses within a pixel or administrative unit (e.g. country), plays an essential role in the estimation of total land changes. Gross land changes affect the magnitude of total land changes, which feeds back to the attribution of biogeochemical and biophysical processes related to climate change in Earth system models. Global empirical studies on gross land changes are currently lacking. Whilst the relevance of gross changes for global change has been indicated in the literature, it is not accounted for in future land change scenarios. In this study, we extract gross and net land change dynamics from large-scale and high-resolution (30-100 m) remote sensing products to create a new global gross and net change dataset. Subsequently, we developed an approach to integrate our empirically derived gross and net changes with the results of future simulation models by accounting for the gross and net change addressed by the land use model and the gross and net change that is below the resolution of modelling. Based on our empirical data, we found that gross land change within 0.5 • grid cells was substantially larger than net changes in all parts of the world. As 0.5 • grid cells are a standard resolution of Earth system models, this leads to an underestimation of the amount of change. This finding contradicts earlier studies, which assumed gross land changes to appear in shifting cultivation areas only. Applied in a future scenario, the consideration of gross land changes led to approximately 50 % more land changes globally compared to a net land change representation. Gross land changes were most important in heterogeneous land systems with multiple land uses (e.g. shifting cultivation, smallholder farming, and agro-forestry systems). Moreover, the importance of gross changes decreased over time due to further polarization and intensification of land use. Our results serve as an empirical database for land change dynamics that can be applied in Earth system models and integrated assessment models.

Reconstructing Taiwan’s land cover changes between 1904 and 2015 from historical maps and satellite images

“…Historical maps are the primary source of land cover information 2–7 . The oldest known topographic map describing Taiwan is the “Map of Tamsuy and nearby villages including the island Kelang” (originally called the “Kaartje van Tamsuy en omleggende dorpen, zoo mede het eilandje Kelang”) made by Dutch colonizers and shows the location of aboriginal tribes and the distribution of vegetation in 1654 8 .…”

“…However the fact that these maps were written in Japanese or Chinese, has likely hampered their inclusion in the global reconstruction efforts led by European and North American researchers 14,16,18 . Following in their footsteps and other regional studies 7,29–31 the objective of this study is to use historical maps and satellite images as the basis for the first high resolution (500 × 500 m), century-long, wall-to-wall reconstruction of land cover changes in Taiwan. The spatial and temporal extent of this objective differs from previous studies 11–13,32 which were limited to a specific city or region.…”

“…The outcome of this effort is expected to contribute to future revisions of global land cover reconstructions (see Table 1 in Fuchs et al . 7 ) as well as to studies of (gross) land cover changes, the carbon budget, regional climate, urban heat islands, and air and water pollution at the national and sub-national scale.…”

Impact of cropland displacement on the potential crop production in China: a multi-scale analysis

“…Differences between net area change and gross area change in cropland have been analyzed at continental and global scales (Fuchs et al 2015(Fuchs et al , 2018. These studies show that gross changes far exceed net changes at these scales.…”

Land cover changes and their determinants in the coral rag ecosystem of the South District of Unguja, Zanzibar

“…In recent decades, land cover change has been considered as one of the major global environmental problems (Fuchs et al, 2018;Nyamugama and Kakembo, 2015;Schoeman et al, 2013;Ouedraogo et al, 2010). It has become an area of interest to many researchers and scientists including bio-geographers, ecologists and natural resource managers to gain deeper understanding of its causes and consequences to the planet earth.…”