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Abstract:
Human activity has fundamentally altered the global phosphorus (P) cycle. Yet our understanding of when and how humans influenced the P cycle has been limited by the scarcity of long-term P sequestration records, particularly outside Europe and North America. Lake sediments provide a unique archive of past P burial rates and allow the human-mediated disruption of the global P cycle to be examined. We compiled the first global-scale and continentally resolved reconstruction of lake-wide Holocene P burial rates using 108 lakes from around the world. In Europe, lake P burial rates started to increase noticeably after ∼4000 calendar years before 1950 CE (cal BP), whereas the increase occurred later in China (∼2000 cal BP) and in North America (∼550 cal BP), which is most likely related to different histories of population growth, land-use and associated soil erosion intensities. Anthropogenic soil erosion explains ∼86% of the observed changes in global lake P burial rates in pre-industrial times. We also provide the first long-term estimates of the global lake P sink over the Holocene (∼2686 Tg P). We estimate that the global mean lake sediment P sequestration since 1850 CE (100 cal BP) is ∼1.54 Tg P yr−1, representing approximately a six-fold increase above the mean pre-industrial value (∼0.24 Tg P yr−1; 11,500 to 100 cal BP) and around a ten-fold increase above the Early-Middle Holocene low-disturbance baseline of 0.16 Tg P yr−1. This study suggests that human activities have been affecting the global P cycle for millennia, with substantial alteration after industrial times (1850 CE).
