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Palaeofire Danger Rating Maps and Earth's Last Major Global Warming Event (Project PyroMap)

Final Report Summary - PYROMAP (Palaeofire Danger Rating Maps and Earth's Last Major Global Warming Event (Project PyroMap))

Project PyroMap – Mapping Changes in Fire Activity in Earths Past.

Project led by Dr. Claire Belcher, wildFIRE Lab, University of Exeter.

Wildfires are fires that burn in Earth’s range of ecosystems, such as forests, shrublands, heathlands and grasslands. The occurrence and distribution of wildfire events is dependent on the type of vegetation in area along with the weather and prevailing climate of the region. Therefore future climate change is anticipated to influence the distribution of wildfire activity across our planet.

Climate has changed many times in Earth’s long multi-million year history; the Earth has experienced millions of years with no ice at all at the poles and other phases when the extent of polar ice sheets reached much further south than they do in the current day northern hemisphere. Therefore major shifts, and indeed smaller shifts in climate, have been studied by Earth scientists for many years.

Reconstructions of ancient wildfire activity, known as palaeofire activity have mostly been achieved by palaeontologists searching for and quantifying the abundance of charcoals which can be found as fossils preserved in many different sediments and rock types; they then interpret variations in the abundance of fossil charcoal as evidence for changes in palaeofire activity. However, the degree to which the properties of wildfires, such as how hot they burn, how rapidly they spread also influences the nature and production of combustion products (including charcoal). As such we don’t really know if different types of wildfire would leave more or less charcoal available to become fossilised in rocks for millions of years. This means that variations in charcoal abundance can be difficult to relate to the original fire, particularly when comparing between different ecosystems and different rock records, making it hard to build direct links between changes in palaeoclimate and palaeofire activity.

Project PyroMap has sought to begin to address this challenge in two ways:

1) The project has aimed to improve our understanding and ability to quantify changes in the abundance of fossil charcoal, so that we might be better able to gain insightful information about changes in palaeofire activity according to shifts in palaeoclimate.

2) PyroMap has sought to develop a technique that does not rely on the fossil record of charcoal at all, but rather seeks to relate shifts in palaeoclimate more directly to mathematical estimates of palaeofire risk.

The idea being that in the future researchers might be able to draw these two approaches together and consider what the likely risk of palaeofire was in relation to palaeoclimate and then in turn compare this to the changes in palaeofire activity as evidenced by variations in the abundance of fossil charcoals.

Project PyroMap has shown that the three-dimensional shape of charcoals is controlled by the type of vegetation that was being burnt, the dynamics of the fire that generated them and how long the particles were transported for (e.g. in rivers) prior to their incorporation in sediments which ultimately form rocks. Because of this, information of each of these processes, particularly aspects of vegetation type, may be inferred from observations of fossil charcoal morphology. However critically we can also show that all three processes ultimately affect fossil charcoal quantification indicating that the method that each scientist chooses to quantify charcoal by (e.g. do they count number of particles or measure the total volume of charcoal particles in a rock) will be strongly effected by variations in the dominant shape of fossil particles preserved. As such we have been able to suggest that if fossil charcoals are to help us decipher the role of fire in the Earth system, all the stages in their formation need to be better understood, and the inseparability of morphometry (shape and size) and quantification must be recognised before accurate estimates of variations in palaeofire activity in Earth’s past can be compared.

In order to develop a new exciting approach that links palaeoclimate to palaeofire risk we have used a method that allows fossil leaves preserved in geologic sediments to estimate basic climatic parameters. By compiling a climate dataset from 30 fossil leaf localities of the same geologic age, project PyroMap then established a novel method that estimates ‘pseudo daily’ palaeoclimatic parameters, which allows the probability of ignition of wildfires to be estimated for ancient ecosystems. Our new approach has been tested on two large Neogene aged datasets allowing us to compare the palaeoclimate and palaeofire risk of one fire prone region and across a country wide spatial scale to the climate and fire risk of the modern day. PyroMap indicates that there have been clearly been changes in climate and fire risk from the study period compared to the present day at the locations studied.

Publications resulting from PyroMap to date can be seen on The University of Exeter’s wildFIRE Lab website (more publications are anticipated soon). The wildFIRE Lab webpages also includes information of the research and exceptional facilities that this exciting new laboratory hosts.

Read more about the Principle Investigator (Dr Claire M. Belcher) of this project at: