All over the world, humans leave their “footprints” on the surface of the land. These land use changes play an important role in nutrition, climate and biodiversity. Scientists from the Karlsruhe Institute of Technology (KIT) have combined satellite data with statistics from the past 60 years and found that global land use changes comprise around 32 percent of the land surface. This makes them about four times as large as previously assumed. The researchers report on their results in the science magazine Nature Communications .
Whether cutting down forests, urban growth, the expansion of agriculture or reforestation: land use changes are diverse and shape human history. “In order to master the global challenges of our time, we have to better understand the extent of land use changes and their contribution to climate change, biodiversity and food production,” says Karina Winkler from the Institute for Meteorology and Climate Research – Atmospheric Environmental Research (IMK-IFU), Campus Alpin of the KIT in Garmisch-Partenkirchen. “Because land use also plays a decisive role in achieving the climate goals under the Paris Agreement.”
Despite the age of satellites, “big data” and the increasing amount of information available, existing studies on land use changes are so far only fragmentary and limited in terms of space or time. A research team from IMK-IFU and Wageningen University in the Netherlands has now combined various free data and developed a new, high-resolution map set called “HILDA +” (Historic Land Dynamics Assessment +). With the help of high-resolution satellite data and land use statistics, he reconstructs global land use changes and their spatiotemporal patterns between 1960 and 2019. “The main difficulty in our work lies in dealing with very different data sets,” explains Winkler. “If, for example, the spatial resolution of land use maps,
The map set shows: Land use changes will affect almost a third of the global land area in just six decades and are thus around four times as large as has been known from long-term analyzes. “However, the changes in land use do not show the same pattern all over the world,” says Winkler. In their study, the researchers point to differences between north and south. Accordingly, in the Global North, for example in Europe, the USA or Russia, the forests have expanded and the arable land has been reduced, while in the Global South, including Brazil and Indonesia, the forest areas have decreased and the arable and pasture areas have increased .
In addition, the speed of land use changes has changed over time. The scientists identify a phase of accelerated land use change for the period from 1960 to around 2005 and a phase of slowed down land use change from around 2006 to 2019. “This trend reversal could be related to the increasing importance of global trade for agricultural production and to the global economic crisis of 2007/2008,” says Winkler.
The new land use data could provide an improved data basis for climate and earth system models – and thus contribute to political debates about strategies for sustainable land use in the future. The data are freely available and can be viewed in an online application.
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