Climate outweighs human effects on vegetation properties during the early-to-mid Holocene

Abstract Controversies exist regarding the extent of past human influence on terrestrial ecosystems and the relative importance of human versus climatic factors in shaping Holocene vegetation. However, there has been no systematic examination of these issues at a global scale. Here we integrate palaeoecological, archaeological, and palaeoclimate data to assess the influence of humans and climate in driving patterns of past vegetation during the early and middle Holocene (8500 - 2000 years before present) as recorded by pollen-assemblage properties. We quantify and summarise the patterns of change in different properties from individual records to a global scale and assess the relative importance of humans and/or climate in influencing them. Additionally, we assess whether the internal relationships among these properties changed through time. While we find evidence that humans have high localized impact on vegetation dynamics in various regions and times periods, when considered globally, humans appear to be a secondary factor, during the early-to-mid Holocene. Our results underscore the value of merging multidisciplinary palaeodata to provide a holistic understanding of millennia-spanning relationships between humans, climate, and vegetation across different spatial scales.