PLANT WAX BIOMARKER PALEO-ECOLOGICAL BASELINES ACROSS THE USAMBARA MOUNTAINS, TANZANIA

The Usambara Mountains in northeast Tanzania are a biodiversity hotspot harboring remarkably rich and diversified plants and animals which may have been endemic to the region since the early Miocene. These mountains are under the direct climatic influence of the Indian Ocean Monsoon and possess an exceptionally stable warm and humid climate regime. They thus serve as a refugium for formerly widespread plant species that once stretched from western through eastern Africa. Nevertheless, anthropogenic burning, logging, and cashcrop farming that began during the German colonial period, have transformed the Usambara Afromontane forest ecosystems, which in turn have altered surface water hydrology to such an extent that many mountain streams have become intermittent.

To date, little is known about the long-term role of deforestation or converting natural Afromontane vegetation to agricultural plantations on local hydrology (i.e., precipitation amount and distribution), as no deep-time climate or environmental records exist for the Usambaras even though it is believed that the forests may have been present in the early Miocene and persisted through periods of climate instability caused by Pleistocene glaciation.

In 2022, we collected 35 ecological baseline samples from both forest reserves and in areas with substantial human-induced landscape change along four altitudinal transects across the East and West Usambara Mountains. We extracted plant wax biomarkers (e.g., n-alkanes) from these samples. Their n-alkane distributions and molecular δ¹³C and δD values are correlated with the current environmental and climatic conditions of the Usambara Mountains, and the established relationships will be used for future reconstructions of paleoenvironments and paleoclimate in the region.