Land use in the Earth system

Group Leader: Julia Pongratz

The vegetation covering the continents has decisive influence on climate, exchanging heat, moisture, momentum, and a variety of chemical materials with the atmosphere. Humans are substantially interfering with this exchange by altering the vegetation cover: on about one third of the Earth's land surface natural vegetation has been transformed to agricultural areas ("anthropogenic land cover change"); on an even larger area the general type of vegetation is kept, but is now managed to some extent by humans ("land management"); and only the rest, a mere quarter of the land surface, remains untouched by direct human influence (although via global climate change, also these regions are indirectly altered by human action).

A multitude of observational and modeling studies has revealed substantial influences of land cover change and land management on climate. For example, about one third of the cumulative anthropogenic CO2 emissions until today has been caused by historical deforestation for agricultural expansion. However, large uncertainties remain with respect to the overall impact on climate: The carbon cycle effects of land cover change/land management are highly uncertain on a large scale, and are often counteracted by biogeophysical effects such as changes in land surface reflectivity (albedo) and turbulent heat fluxes.