I am particularly interested in uncovering paleoenvironmental changes and species responses under the pressing influences of climate change. My current research aims to reconstruct landscapes and wildfire activity across temperate and subtropical Australia in response to human activities and climatic change. I specifically work on pollen-based modelling to reconstruct the vegetation within Indigenous-curated landscapes and post-colonial management implications.
Latest relevant publications:
Mariani, M., Connor, S., Theuerkauf, M., Herbert, A., Kuneš, P., Bowman, D., Fletcher, M.-S., Head, L., Kershaw, P., Haberle, S., Stevenson, J., Adeleye, M., Cadd., H., Hopf, F. & Briles, C. (In press). Disruption of cultural burning promotes shrub encroachment and unprecedented wildfires. Frontiers in Ecology and the Environment.
Recent catastrophic fires in Australia and North America have raised broad-scale questions about how the cessation of Indigenous burning practices impacted fuel accumulation and structure. For sustainable coexistence with fire, we need to better understand the ancient nexus between humans and flammable landscapes. We use novel palaeoecological modelling and charcoal compilations to reassess evidence for changes in land-cover and fire activity, focusing on southeast Australia before and after British settlement. We provide the first quantitative evidence that the region's forests and woodlands contained fewer shrubs and more grass before colonization. Changes in vegetation, fuel structures and connectivity followed different trajectories in different vegetation types. The pattern is best explained by the disruption of Indigenous vegetation management caused by British colonization. Combined with climate change impacts on fire weather and drought the widespread absence of Indigenous fire management practices likely preconditioned fire-prone regions for wildfires of unprecedented extent.
Mariani, M., Fletcher, M.-S., Haberle, S., Chin, H., Jacobsen, G., Zawadzki, A. - Climate change reduces resilience to fire in subalpine rainforests. Global Change Biology, 25: 2030- 2042.
Climate change is affecting the distribution of species and the functioning of ecosystems. For species that are slow growing and poorly dispersed, climate change can force a lag between the distributions of species and the geographic distributions of their climatic envelopes, exposing species to the risk of extinction. Climate also governs the resilience of species and ecosystems to disturbance, such as wildfire. Here we use species distribution modelling and palaeoecology to assess and test the impact of vegetation-climate disequilibrium on the resilience of an endangered fire-sensitive rainforest community to fires. First, we modelled the probability of occurrence of Athrotaxis spp. and Nothofagus gunnii rainforest in Tasmania (hereon "montane rainforest") as a function of climate. We then analysed three pollen and charcoal records spanning the last 7,500 cal year BP from within both high (n = 1) and low (n = 2) probability of occurrence areas. Our study indicates that climatic change between 3,000 and 4,000 cal year bp induced a disequilibrium between montane rainforests and climate that drove a loss of resilience of these communities. Current and future climate change are likely to shift the geographic distribution of the climatic envelopes of this plant community further, suggesting that current high‐resilience locations will face a reduction in resilience. Coupled with the forecast of increasing fire activity in southern temperate regions, this heralds a significant threat to this and other slow growing, poorly dispersed and fire sensitive forest systems that are common in the southern mid to high latitudes.
Mariani, M., Holz, A., Veblen, T., Williamson, G., Fletcher, M.-S., Bowman, D. - Climate change amplifications of climate-fire teleconnections in the Southern Hemisphere. Geophysical Research Letters, 45, 5071-5081.
Recent changes in trend and variability of the main Southern Hemisphere climate modes are driven by a variety of factors, including increasing atmospheric greenhouse gases, changes in tropical sea surface temperature, and stratospheric ozone depletion and recovery. One of the most important implications for climatic change is its effect via climate teleconnections on natural ecosystems, water security, and fire variability in proximity to populated areas, thus threatening human lives and properties. Only sparse and fragmentary knowledge of relationships between teleconnections, lightning strikes, and fire is available during the observed record within the Southern Hemisphere. This constitutes a major knowledge gap for undertaking suitable management and conservation plans. Our analysis of documentary fire records from Mediterranean and temperate regions across the Southern Hemisphere reveals a critical increased strength of climate-fire teleconnections during the onset of the 21st century including a tight coupling between lightning-ignited fire occurrences, the upward trend in the Southern Annular Mode, and rising temperatures across the Southern Hemisphere.
The following funded projects are ongoing:
- Fuels for fire: quantifying vegetation through changing climates in Australia (Leverhulme Trust)
[Leverhulme Trust Newsletter - May 2023 by Leverhulme Trust - Flipsnack, PI: Michela Mariani ]
Project summary: In Australia, the unprecedented wildfires of 2019-2020 sparked debates around managing forest fuel loads in a context of climatic warming and increased fire risk. Reinstating Indigenous cultural burning is gaining momentum as an option for mitigating such disastrous events, but empirical evidence for its efficacy is limited. This fellowship aims to quantify vegetation cover across southeast Australia through a phase of rapid warming analogous to the present, but during which management was only carried out by Indigenous peoples (i.e. Late Pleistocene). This reconstruction will be compared to present-day fuel dynamics derived from decades of post-colonial fire suppression and rising temperatures.
- Has it always burned so hot? Fuel and fire changes in southeast Australian forests (Australian Research Council) [ARC Research Project - PF-FIRE (unimelb.edu.au), funded by the Australian Research Council Indigenous Grants scheme; PI: Michael-Shawn Fletcher]
Project summary: Indigenous cultural burning has been raised as a way of mitigating against climate-driven catastrophic bushfires in southeast Australian forests. It is argued that returning an Indigenous style fire regime will keep landscape fuel loads low, thus reducing the frequency and intensity of bushfires and mitigating against large catastrophic bushfires. To explore this further and advocate for policy change, this project aims to bring together the enormous reservoirs of traditional fire knowledge in Indigenous communities with data-driven science by empirically testing how fuel loads, fuel type, fire frequency and fire intensity have changed in southeast Australian forests during the transition from Indigenous to British management over the past 500 years.