Relative air humidity can be used as a practical and strategic indicator to decide when to carry out controlled or prescribed burns. This is what the... A new study by ISPN technical advisor and Integrated Fire Management (IFM) researcher, Lívia Carvalho Moura, and collaborators., under the guidance of Professor Dr. Isabel Schmidt, published in the International Journal of Wildland Fire.
The research, titled "Relative air humidity at the time of burning is a fundamental predictive factor of fire behavior in the Cerrado," analyzed how different conditions—such as time of year, time of day, and amount of dry vegetation (fuel)—influence fire behavior. Among all these factors, air humidity stood out as one of the most decisive in guiding operational decisions in the field.
“The idea for the study stemmed from management questions posed by the manager of the Chapada das Mesas National Park at the time, Paulo Adriano Dias, co-author of the work. Observing the traditional fire management practices of local communities and indigenous peoples in the region, he wanted to know how to measure vegetation and climate indicators associated with these traditional practices for use in technical protocols,” explains Lívia Moura Carvalho.
“Knowing the right time to use fire in a controlled way seemed very obvious to the people and communities of the region, but for many managers and researchers it was not very clear or perceptible, and above all there was a concern about transmitting and making this knowledge available,” adds Lívia.
A simple variable
The survey results show that lower levels of air humidity are associated with more intense and rapid fires; while higher humidity levels result in milder, slower fires that are easier to control.
This means that the same area can exhibit very different fire behaviors depending solely on the conditions at the time of burning—especially the humidity throughout the day and the amount of combustible material.
Accessible tool
In practice, the study demonstrates that relative air humidity can be incorporated as an objective criterion to guide when and how to carry out planned burns. Because it is an easy variable to measure in the field, it becomes an accessible tool for firefighters and managers.
Air humidity levels above 50% are more common during the rainy season and the beginning of the dry season (between April and June, depending on the region), more specifically in the late afternoon or early evening, when temperatures are lower and the air tends to retain more moisture.
Context
In the Cerrado biome, fires in native vegetation are increasing due to extreme weather events and climate change, as well as a lack of management of accumulated dry biomass. The problem is more pronounced at the end of the dry season, with more intense and severe fires. Since 2014, prescribed burns have been applied in some protected areas at the beginning of the dry season to manage vegetation adapted to or prone to fire, within the framework of the [missing information - likely a program or initiative]. Integrated Fire Management (MIF).
The research results also reinforce the role of MIF (Integrated Fire Management), adopted in reducing fires in protected areas of the Cerrado. This approach can include the use of prescribed burns in fire-adapted vegetation at the beginning of the dry season to fragment fuel and reduce the amount of dry vegetation in the landscape.
By using air humidity as a criterion for determining the timing of these burns, it is possible to increase the safety of operations and reduce the risk of large-scale fires at the end of the dry season, which are more intense and difficult to control.
Thus, the study highlights how scientific knowledge can support practical decisions, making the use of fire more efficient, safe, and aligned with the conservation goals of the Cerrado.
