Gross changes in reconstructions of historic land cover/use for Europe between 1900 and 2010

Abstract

Historic land-cover/use change is important for studies on climate change, soil carbon, and biodiversity assessments. Available reconstructions focus on the net area difference between two time steps (net changes) instead of accounting for all area gains and losses (gross changes). This leads to a serious underestimation of land-cover/use dynamics with impacts on the biogeochemical and environmental assessments based on these reconstructions. In this study, we quantified to what extent land-cover/use reconstructions underestimate land-cover/use changes in Europe for the 1900-2010 period by accounting for net changes only. We empirically analyzed available historic land-change data, quantified their uncertainty, corrected for spatial-temporal effects and identified underlying processes causing differences between gross and net changes. Gross changes varied for different land classes (largest for forest and grassland) and led to two to four times the amount of net changes. We applied the empirical results of gross change quantities in a spatially explicit reconstruction of historic land change to reconstruct gross changes for the EU27 plus Switzerland at 1 km spatial resolution between 1950 and 2010. In addition, the reconstruction was extended back to 1900 to explore the effects of accounting for gross changes on longer time scales. We created a land-change reconstruction that only accounted for net changes for comparison. Our two model outputs were compared with five commonly used global reconstructions for the same period and area. In our reconstruction, gross changes led in total to a 56% area change (ca. 0.5% yr(-1)) between 1900 and 2010 and cover twice the area of net changes. All global reconstructions used for comparison estimated fewer changes than our gross change reconstruction. Main land-change processes were cropland/grassland dynamics and afforestation, and also deforestation and urbanization.

Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes

“…Collectively, these findings suggest that urban point sources of nutrients were the leading factor explaining the spread of lacustrine hypoxia in Europe over the past few centuries. The prevailing importance of urban point sources of nutrients as the preeminent trigger toward the spread of hypoxia was also validated by M-K and AMM analyses of decadal-scale landscape and climatic reconstructions spanning the period between CE 1900 and 2010 (24) (Fig. 4 and Figs.…”

“…Additionally, European high-resolution datasets (23,24) allow for investigations to be conducted at the scale of individual lake watersheds. The present study relies on existing datasets of changes in land cover at the watershed scale [Historic Land Significance Using a compilation of data arising from over 1,500 European watersheds, we have identified the relative role of different drivers in initiating hypolimnetic hypoxia, a critical indicator of lake health.…”

Processes and driving forces in changing cultural landscapes across Europe

“…In a pan-European analysis of the twentieth century LULC change, Fuchs et al (2015) determined land abandonment (cropland to grassland), afforestation and cropland expansion to be the most important landchange processes. A recent review of studies looking at driving forces of landscape change in Europe (Plieninger et al 2016) similarly determined ''land abandonment and agricultural extensification'' as the most prominent ''proximate driver'' (i.e.…”

Europe: the paradox of landscape change : A case-study based contribution to the understanding of landscape transitions

“…Afforestation seems dominant over deforestation in all areas, except for Portofino where large wild fires have resulted in a decrease in forest area. Fuchs et al (2015) estimated gross land cover change based on empirical data for some 10 years, and found 6% of increase of urban area, some 20% change from grasslands to cropland and 19% increase of forests. Compared to these figures, changes in the case studies are relatively small.…”

“…In the present paper the use of a timeframe of almost 25 years may conceal that large changes and in fact opposite changes have occurred in the preceding period. Fuchs et al (2015) reconstructed the change during the 20th century based on global data sets, and found that overall change was as much as 56%, and the Mediterranean region was considered a hotspot for change (Fuchs et al 2013). For the Netherlands it has been well documented how the forests, heathlands and moors were converted to productive land already at the beginning of the 20th century, tremendous changes occurred in the 1960s as a result of land rationalization: removal of landscape elements, hedgerows, single trees, ponds, natural brooks etcetera .…”