Holocene palaeoenvironmental change in Amazonia’s largest known peatland complex

Tropical peatlands are important for carbon storage and sequestration, biodiversity, and a wide range of other ecosystem services, but they are under pressure from resource exploitation, climate change, commercial agriculture, and infrastructure expansion. Through their rich palaeoecological records, these water-logged landscapes offer a unique opportunity to understand long-term vegetation dynamics of tropical peatlands and, importantly, their interactions with the physical environment, the global carbon cycle, and the local communities who rely on their resources. Improving our understanding of long-term peatland development contributes critical underpinning evidence to support their conservation and management and provide information about their sensitivity to changes in climate and hydrology. In this presentation we synthesize more than a decade’s work by our research group in pioneering the palaeoecological study of the largest known peat-forming wetland complex in Amazonia, the Pastaza-Marañón Foreland Basin (PMFB). This body of work, including around twenty palaeoecological sequences, allows a reappraisal of earlier ideas about the spatial and temporal structure of the wetland complex. Our analysis shows that, with caveats, palynology and associated proxy methods can be used successfully to reconstruct past vegetation changes. For example, the palaeoecological data challenge earlier attempts to classify the vegetation of the PMFB into ‘types’, suggesting instead that plant communities vary gradually in time (as they do, often, in space) between a wide variety of end-members. At many individual sites, likely those occupying abandoned river channels, endogenous processes (infilling, plant succession) dominate the pattern of peatland development and local environmental change over time. These patterns are largely predictable and comparable to hydroseres known elsewhere, though many details remain unexplored. At some herbaceous or lightly wooded sites, palaeoecological data confirm that similar vegetation has persisted for many thousands of years without succeeding to closed-canopy woodland, apparently maintaining an equilibrium with hydrological conditions. Overall, our palaeoecological data are informing our conceptualisation of the processes of change in these landscapes, which in turn are finding applications in policy development and sustainable management at global, national and local scales.