Ancient ecological boundaries have been disrupted: what is propelling Earth toward a fiery equivalent of the Ice Age?

In recent years, wildfires have repeatedly erupted across the globe: in the USA, Canada, Australia, Portugal, and Greece. As a result of these massive forest fires, vast areas have been burned, while others have been shrouded in smoke, reports Science Alert.

The continuous interaction between humans and fire has spanned our entire existence as a species. Fire practices have become so extensive, especially in recent centuries, that people, according to Stephen Pyne, an emeritus professor of natural sciences at Arizona State University, are effectively creating a fiery equivalent of the Ice Age.

Humanity and fire have been reshaping the Earth since the end of the last ice age, approximately 11,500 years ago. Generally, scientists believe that all these changes have made the planet's landscapes more susceptible to fire.

Recent studies suggest that mass depopulation, particularly in America, which removed the "torch" and allowed forests to reclaim land while sequestering more atmospheric carbon, likely helped propel the planet into a minor ice age from the mid-16th to the mid-19th centuries.

However, there have been limits. Fire and life have co-evolved over 420 million years. During this time, ecological costs and checks have constrained how far humans could "push fire" within the boundaries of terrestrial landscapes. Unfortunately, this process has accelerated and altered its nature—this is tied to the mass burning of fossil fuels or what scientists refer to as lithic landscapes. Now, researchers believe that this combustion exceeds old boundaries: fire can ignite anytime and anywhere, and its byproducts are not easily absorbed by the old ecology.

Essentially, such combustion heats the Earth's atmosphere and is a primary driver of climate change, while also improving overall conditions for wildfires to occur. According to Professor Pyne, the shift to a fossil-fuel civilization has also influenced how people live today: designing cities and communities, shaping living landscapes, generating and transmitting energy, and using fire.

Chemicals from fossil biomass replace or attempt to substitute the ecological effects of fire. Energy from fossil fuels displaces the heat, light, and power of flames. In Pyne's view, instead of challenging wildfires with controlled fire, modern communities combat landscape fires through industrial fire countermeasures using pumps, engines, bulldozers, and airplanes.

This "pyric transition" in burning types causes two different kinds of fire—fires in living landscapes and fires that consume lithic landscapes—to interact in ways that sometimes compete and sometimes cooperate. Scientists believe this has led to the intersection of two realms of fire, often with deadly consequences.

Climate change acts as a powerful amplifier of performance, drawing increasing attention, and its impact extends far beyond fires. According to Professor Pyne, debates today focus on what is more important—climate or land use. However, the framing of the question is, in the scientist's view, erroneous: both arise independently from the transition to a fossil-fuel-based society. It seems that megafires are fueled by modernity, just as hurricanes are fueled by warm oceans.

For instance, the pyric transition triggered a series of monstrous fires in the USA at the end of the 19th and beginning of the 20th century—during the final decades of the Little Ice Age. This chaos inspired local governments to end ecological collapse, making fire suppression foundational. With the disappearance of natural fire and traditional burning from the landscape, fire populations dropped to a point where flames could no longer perform the necessary ecological work. Instead of reducing risk, landscapes became prone to more explosive burning as fuel accumulated over decades.

Now, too much fossil biomass is being burned on Earth for emissions to be absorbed within ancient ecological boundaries. Fuel in living landscapes accumulates and restructures, while the climate spirals out of control. When fire returns, as it should, it too often arrives in the form of wildfires.

According to Professor Pyne, looking at the world picture overall reveals that the Earth is essentially entering a new fiery period, comparable to the glacial periods of the Pleistocene, with a pyric equivalent of ice sheets. This is a new era where fire is the primary driver and main expression.

The fiery power of humanity underpins the Anthropocene, which is the result of not just anthropogenic intervention, but one made possible by humanity's monopoly on fire. Unfortunately, the interaction between the two realms of fire, in living and lithic landscapes, remains insufficiently studied. According to Pyne, if we tally all the effects we observe today, it becomes clear that the Earth has already entered a fiery epoch equivalent to an ice age.