Long-term interactions between vegetation, fire and human impact in the Neotropics, with a case study from Guyana

Reconstructing past environmental changes creates an insight into how ecosystems have responded to disturbance regimes and natural climate variation. Fire is just one example of a disturbance regime that has and still is actively altering ecosystems across the Neotropics. Through the reconstruction of Holocene fire patterns and vegetation changes, the drivers of fire can be understood. Climate has naturally impacted fire regimes for millennia while the impact of humans as a driver of fire is still something that is not completely understood. This thesis explores long term interactions between humans, fire and vegetation in the Neotropics at a regional scale and a local scale in the Rupununi savanna, Guyana.

Through the creation of the Reading Palaeofire Database (RPD) significant improvements including data quality and new age models have been made allowing advancement in the availability of historical fire data. This allowed a new Holocene composite curve to be created representing changing patterns of biomass burning. This has been used to test the impact of population growth and decline throughout the Holocene using a Summed Probability Distribution curve of archaeological material.

Identified as a data gap through the creation of the RPD, a new high-resolution charcoal, pollen and non-pollen palynomorph record has been created for Amoko, a wetland site in the North Rupununi, Guyana. This data reveals the sustained presence of savanna throughout the past 8,400 years, confirming that not all northern South American savannas share the same history of vegetation changes. Amoko is closely tied to the edaphic conditions at the site, with the arrival of Mauritia flexuosa the most significant change in the record closely tied to the site’s hydrology. Furthermore, through examination of the last 600 years of the Amoko record, it reveals that even though Guyana had no fire policy, Indigenous fire was still used in a sustainable way with no impact on the vegetation.