Non-native pollen of Himalayan balsam ( Impatiens glandulifera ) can be utilised as a stratigraphic marker of the Anthropocene in the UK

Impatiens glandulifera (Himalayan balsam) is a non-native plant species that has become widespread in the UK. Observational records indicate its arrival in the early 19th century as an ornamental plant, but it did not become widespread until the post WWII interval. In this paper, we demonstrate that I . glandulifera leaves a fossil signature in sediment cores from the River Soar in Leicestershire, with 210 Pb dating confirming its primary palaeontological record from the 1930s, shortly after it was first recorded in this region, and is more persistent and abundant in core deposits since the 1960s–70s, after which it is known to have proliferated in the wider landscape. Changes in the associated pollen assemblages in the cores suggest that its spread impacts on other plants in the local community. The record of persistent occurrence of I . glandulifera in the cores can be used to correlate Anthropocene deposits between sites along the River Soar and could be aligned with the fossil signature of other non-native pollen, for example common ragweed ( Ambrosia artemisiifolia ) to provide a biostratigraphical tool for identifying and correlating Anthropocene deposits more broadly.