The Interaction Between Humans and Fire in a Changing World

Members of the Princeton Township fire crew carrying hose and going into action against fire. Princeton, Massachusetts, 1939 | B. W. Muir, U.S. National Archives | Public domain

Fire and ecosystems

Ever since terrestrial ecosystems came into being, wildfires have formed an integral part of their dynamics. They have been occurring since plants first covered the surface of the continents, some 420 million years ago. They were favoured by the oxygen-rich atmosphere that had been built up over millions of years, since the appearance of microorganisms capable of photosynthesis. These fires were sparked by lightning or volcanoes, and they became even more frequent when grasses and other particularly flammable herbaceous plants expanded into regions with a dry climate.

Since then, fire has applied an evolutionary pressure that has forced species to adapt. Some plants have evolved to take advantage of fires and produce fruits – called serotinous fruits – that need fire to release their seeds. After the flames, with the competition from other species eliminated, their seeds then find suitable conditions for germination. In Catalonia, Aleppo pines and maritime pines produce this type of fruit. In California, the continuance of the sequoia populations relies on surface fires that burn the leaf litter and help to open the cones, allowing new saplings to establish. Many animal species also depend on fire: emblematic examples are the condor on the American continent and the Bonelli’s eagle in the Iberian peninsula, which prefer habitats opened up by recurrent fires, where they are able to find prey.

Humans have also coexisted with fire since the beginning of their history. Approximately 400,000 years ago, they began to control fire, using it as a tool to guarantee the survival of populations across all continents. Some of these ancestral practices can still be recognised  among the peoples of California. The Chumash people of the Santa Barbara region used fire to keep areas free of undergrowth, allowing them to spot grizzly bears from a distance. The Yurok of northern California used fire to encourage the straight regrowth of many hardwood species, essential for making baskets and everyday tools. For the Maidu, who lived in the foothills of the Sierra Nevada, the frequent use of fire in open oak forests stimulated the growth of “Indian potatoes” – edible plants promoted by fire though competition and litter elimination. Closer to home, from the Pyrenees to the Atlas Mountains, fire was traditionally used as a key management tool for maintaining pastures, as it eliminated scrub vegetation and stimulated the growth of grasses favoured by herds.

In all these cultural contexts, fire is a powerful, ever-present companion and a benefactor of everyday life: it provides warmth, nourishment, protection, and the means to build tools. In many cases, it also becomes a spiritual force. Fire shapes cultural landscapes, creating open spaces and reducing flammable vegetation. It also regulates the functioning of ecosystems, aiding the decomposition of organic matter and the release and recycling of nutrients, especially in arid environments where biological processes are slow. As long as humans keep the frequency and intensity of fires within certain limits, the nutrient balance can be maintained, the soil preserved, and plants and animal species allowed to flourish, to the point that some of them even become dependent on this system of manmade fires. In this way, fire becomes an agent of renewal and diversification. But fire can also become an uncontrolled, destructive force. The Greek myth of Prometheus recognises the value of fire zealously guarded by the gods and stolen for the benefit of humans, even though the acquisition of its power comes at great cost. The key lies in knowing how to control it, or fleeing before it is too late.

Fire in the 21st century: from tool to threat

As we find ourselves well into the 21st century, we are seeing how fire has become a problem for most societies. The fundamental change in the relationship between humans and fire came with industrialisation and the demographic shifts from rural areas to cities. The burning of fossil fuels completely changed the relationship between humans and fire and its interaction with landscapes. New technologies increased our capacity to control fire, which became confined to furnaces and engines where vast amounts of energy are released. The transformative capacity of this unleashed energy also impacts landscapes, sometimes in unexpected ways. The migration of rural populations to cities and the concentration of agricultural activity in more productive areas thanks to powerful fossil-fuel machinery has led to woody vegetation reclaiming large areas that, until a few decades ago, were used for agriculture and livestock grazing. At the same time, the people in these societies have lost their daily connection with fire and the knowledge of how to use it to manage the landscape. In fact, in many places, the policy of extinguishing all fires has led to an increase in forest vegetation. Finally, we see how urban populations, in their eagerness to seek contact with nature, are moving into these wooded areas, which are now much more flammable. Fuel builds up in the landscape and the historical pattern of ignitions and contact between humans, fire and vegetation is altered.

At the same time, the gasses produced by the mass burning of fossil fuels are generating an ever warmer and more extreme climate. Climate change is bringing about conditions highly conducive to the rapid spread of fires in many places where this was previously rare. Vegetation becomes more prone to burning: the rising temperatures increase the demand for water, making plants more stressed. Furthermore, in many parts of the world, more irregular rainfall is leading to longer and more pronounced periods of drought, limiting the water available to plants and putting them under even greater stress. The introduction of invasive species has also altered the natural fire cycle, in many cases changing the flammability of the landscape and the frequency of fires.

All of this means that fires are becoming increasingly difficult to control. What was once a regenerative force is now becoming destructive. In recent decades, we have begun to hear about megafires and the devastating losses they cause. The consequences of this are not only felt by humans: frequent fires mean that many species do not have enough time to generate new seeds and re-establish themselves. The severity and extent of the fires leads to widespread mortality of the biota and a homogenisation of the landscape that reduces biodiversity. Thus, the historical relationship between fire, humans and ecosystems is lost.

Given the climate emergency in which we are immersed, people and governments everywhere are wondering what we can do to face a situation that seems not to be improving, but degenerating. The answer is not simple, and there is no magic solution. Our society often views fire as if it were exclusively a problem to be solved with more resources: more firefighters and more waterbombing craft, in the hope that technology will solve the problem. But our technological capabilities can only control the new scenario to a certain extent. The current imbalance between fire and vegetation has reached a point where the energy released by fires far exceeds our technical capacity to contain them. With this in mind, we must rethink our relationship with fire and promote systems that allow fires to generate more benefit than harm.

First and foremost, we must recognise that forest fires are a complex socio-ecological phenomenon, where physical, ecological, socioeconomic, historical and cultural processes converge. Then we will be able to analyse their different components. For example, there is a great need to continue investing in research to better understand the physical processes that govern the spread of extreme fires. At the same time, the current climate trend must be addressed: stabilising and reversing global warming is essential to reduce the atmospheric energy that sustains fires. In addition, there is a broad consensus on the need to work towards less flammable landscapes – in other words, those with a lower fuel load – as this would reduce the spread and intensity of fires and make them easier to control.

The socio-economic mechanisms that allow for a more fire-resilient landscape are complex, variable, ephemeral and specific to each region. Although technological advances will continue to be an important factor in responding to many risks, they will not be enough. At the same time, the often-celebrated revival of traditional practices must be approached with an understanding of local conditions, backed up by scientific knowledge. While in some areas a return to silvopastoral practices may be appropriate, in others, a shift to land uses that include activities such as horticulture may be a better option. Even so, the recovery of traditional fire use in a way that aligns cultural and economic interests with risk prevention could offer a solution in many contexts, although it will not be applicable everywhere, for example in densely populated areas. A better understanding, contextualisation and implementation of many of the ancestral uses of fire could be very beneficial for ecosystems and the societies living within them. Thus, we must redefine our relationship with ecosystems within boundaries of sustainability that guarantee the services they provide. In this way, fire can go from being a threat to an ally, and its judicious use can even help to regulate the functioning of ecosystems, supporting their biodiversity and the societies that inhabit them.