This article appeared in Daily Timber News, 22 August 2022
Climate change threatens our forests, but it is not necessarily an existential threat, according to a leading Australian scientist.
“It’s not necessarily the case that we will be wiped out by wildfire. The existential threat of fire can be mitigated, but we must use ALL knowledge,” Mark Adams, Professor of Bioscience and Innovation at Swinburne University of Technology and former Dean of the Faculty of Agriculture and Environment at the University of Sydney, told an international forum. This included indigenous people’s use of fire as a management tool.
Australia was not always a “land of fire”, he said. “You can have fire and snow in the same place – that’s an important thing to understand.”
Professor Adams, a member of the Experts’ Panel for the 2009 Victorian Bushfires Royal Commission, has received numerous international fellowships and awards for his work on biology and ecology of Australia’s forests, woodlands and ranges. He was addressing an online global audience organised by Frontiers Forum.
He placed his ideas in the context of the role of fire in Earth’s history: fire had been in the vegetation record for 400 million years, increasing in hotter and drier periods and less in wetter and cooler periods.
From the first appearance of hominids 400,000 years ago to the emergence of modern humans 40,000 years ago, fire became an indispensable part of life, from heating, cooking and ecosystem management.
Indigenous peoples, such as Aboriginal Australians, realised that more fire could reduce the frequency of woody plants and increase grasses and herbaceous species. “This was important knowledge gained early, still being practised today,” he said.
Professor Adams said the industrial revolution in the 18th Century drove further the ‘Great Separation’ between traditional communities and urban life, where fire became feared and infused with a sense of horror. However, people in rural and regional areas broke this dichotomy. “Rural and regional bear the load of urban ideas imposed from capital cities most affected by the current fire crisis,” he said.
They lived near woodlands and either had direct knowledge of fire or had learnt how to cope. “Their problem is the imposition from capital cities of policies and practices that are devised by people with no first-hand experience of living with fire,” he said.
Professor Adams said that in the US, a campaign to warn of fire as a threat had been too successful. Extinguishing all fires became part of policy, but this made the problem worse. “The fuel continues to accumulate; the fire next time is hotter and more difficult to control,” he said.
The wealthy US learnt that all its technological resources – helicopters, aeroplanes, satellites, drones – could not extinguish fires. Technology alone was not the solution; Professor Adams said we needed to learn from history – changes in fire regimes were completely tied to changes in climate.
“The existential threat of fire can be mitigated, but we must use all knowledge – not just better aeroplanes and satellites, but also the knowledge of indigenous people acquired over tens of thousands of years,” he said.
Professor Adams said current scientific research said the climate was now changing due to more greenhouse gases in the atmosphere. This was reflected in the changing air temperature, but these had only risen by a degree or two.
“The change in air temperature changes the humidity – the amount of water vapour the atmosphere can hold,” he said. The vapour pressure deficit was the difference between the maximum amount of water the atmosphere can hold and actually holds. “As the temperature rises, the vapour pressure deficit is increasing,” he said.
Professor Adams said a global map over a 100-year timescale, from 1901-2017, showed the atmosphere in parts of the world was getting drier – “but not everywhere”. The atmosphere was drier in north Africa, parts of central Australia, western USA, part of south Amazon and the Middle East, but areas had also got wetter – northern Australia, the west coast of South America, the eastern US, south-east Canada and the Congo.
“The changes in atmosphere water content and changing evaporative power are not universal. These changes in the atmosphere are also being mirrored in changes in vegetation,” he said.
Professor Adams said rising CO2 in the atmosphere caused changes to the water use efficiency of plants over the same 100-year period. Research showed that every decade, the water use efficiency in the world’s forests increased. The greatest increase in water use efficiency came during the Great Depression and the decade after WWII – the two decades of the least increase in CO2.
“The trees in the forests are conserving water and using less water in growth and taking up carbon,” he said. “These two features – the change in atmosphere and the change in the vegetation use of water – are part of global efforts to model climate.”
The increase in water use efficiency was called physiological forcing. “All of the world’s current models on future climate include physiological forcing,” he said.
The crux of the issue was that with the trees using less water, there was more water in soils and more runoff. “If trees are using less water, that means less water to come back as rainfall. In parts of the Amazon, there is reduced rainfall, in other parts more rainfall. This is a feature of climate, local and up to regional scale. The important message is that the trees in the forests affect the climate themselves, in the same way as the atmosphere responds to changes in temperature,” he said.
“These two forces – drier atmosphere and reduced transmission by trees – are effectively opposing forces when it comes to fine fuel – the litter layer that fits on the surface of forests. “If the atmosphere is drier, the litter layer would be drier and also understorey vegetation, but if the overstorey trees are using less water, that means the soil is wetter, the litter layer is wetter and understorey shrubs wetter. These are opposing ideas when it comes to the litter layer, one of the most important elements in the flammability of forests.”
Professor Adams said this conundrum could not be resolved at present. “We don’t know which of these two forces, the drier atmosphere or trees using less water, will prevail. Will the litter be drier or wetter – or can it be both? That is perhaps is what is happening – you can have both,” he said.
In certain times of the year the litter, shrubs and forest could be more flammable from a changing climate. “The same litter could be wetter at different times of the year, also due to a changing climate. These are really important questions that need to be resolved.”
Professor Adams said opinions varied about how good models are. In Australia, fire models were often quite different from what really happened in fires. “The models are not doing a great job of predicting fuel load. In the area of forest where we have uncertainty – fuel – we can make a difference by modifying fuels in the short term,” he said.
Fire in essence was driven by oxygen, fuel and ignition. “We can’t do anything about oxygen, we can’t do much about lightning strikes – that leaves us with one – fuel,” he said.
More maps of fire activity were not needed; research should concentrate on physical fire research – how combustion works, how fires spread. “That’s not an easy field. It needs to be refreshed to try and get a better understanding of the fine grain risks in climate change envelopes, particularly at the local and regional stages,” he said. Crucially, “we need to bring together the knowledge of indigenous peoples in how to manage forest and woodland around the world”.
Professor Adams highlighted five rules. “Research must be rigorous; must be open, transparent and well communicated; soundly based; multi-disciplinary and targeted to solutions. It’s easy to do lots of research that will quantify the problem; try doing research that focuses on solutions for a change,” he said.
“Extinguishing the fire crisis? We can’t extinguish the fires, it’s pointless to try. We can extinguish the crisis by using science.”
