Multi-proxy reconstruction of environmental dynamics and colonization impacts in the Mauritian uplands

A 115 cm long sediment core retrieved from the exposed uplands of Mauritius, a small oceanic island in the Indian Ocean, shows environmental change from the uninhabited era into post-colonization times. Well-preserved fossil pollen and diatoms in the uppermost 30 cm of the core reflect environmental conditions during the last 1000 years. Granulometric analysis along the core shows that the sediments below 30 cm consist of weathered material and that the record may contain hiatuses. This is also illustrated by a 14C date at 96 cm depth of 35,000 calibrated years before AD 1950 (35.0 cal ka). The pollen record shows that pristine vegetation at 650 m elevation consisted of ericaceous heathland and Pandanus marsh. Around 0.9 cal ka wet montane forest and fern-rich marsh replaced heathland vegetation, indicating higher moisture availability. Natural changes in upland vegetation associations are mainly driven by changes in sediment accumulation causing changes in soil properties and drainage conditions. The historically well-dated start of colonization (AD 1638) is reflected by the sudden arrival of exotic plant taxa Camellia sinensis (tea), Pinus spp. (pine), Casuarina equisetifolia (coastal she-oak), Psidium cattleianum (strawberry guava), Homalanthus (Queensland poplar) and Saccharum officinarum (sugar cane), as well as an increase in charcoal, indicating deforestation.