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Editorial: Past interactions between climate, land use, and vegetation
Climate and land use changes and their respective impact on vegetation composition, plant abundance, plant diversity and biodiversity in general is a challenging topic. For evaluating the current status of climate-land use-vegetation relationships, a baseline is needed. For this purpose, paleoecology, paleoclimatology, history and archaeology should be combined. However, combining data from various disciplines is not straightforward due to differences in the meaning of the data and their spatial and temporal resolutions.
To explore the past interactions between vegetation, climate and land use, Reitalu et al. (2013), Marquer et al. (2017) and Kuosmanen et al. (2018) used statistical approaches (variation partitioning and redundancy analysis) to combine pollen-based vegetation estimates, land use data (anthropogenic land cover scenarios, population density estimates and fire) and climate (climate simulations). These studies underline a potential tipping point related to the human impact on ecosystems around 4,500–4,000 years ago resulting from the spread of agriculture and the rise in human population size. However, the climate influence increased again over the last millennium due to late-Holocene climate shifts and specific climate events that are likely to have influenced both vegetation and land use.
In order to better understand these trends, more studies are needed, in particular by using a large variety of land use and climate variables based on proxies (Figure 1). Many variables based on empirical data (e.g., chironomids and historical information) are unlikely to cover a large spatial scale. In contrast, temperature, drought, and precipitation estimates inferred from tree-ring chronologies are available for regional to sub-continental scales (e.g., Cook et al., 2015; Büntgen et al., 2016; Esper et al., 2016; Ljungqvist et al., 2020; Tegel et al., 2020), although they mostly cover only the last millennium. Dendrochronological studies further provide information about historical land use (e.g., forest management) and tree-growth responses to climate changes. There is, therefore, a great potential for combining tree-ring proxies with pollen-based vegetation data to quantify the effects of climate and land use on vegetation.