Skip to main content

Drivers and projections of global fire activity and intensity under future climate and societal changes.

Periodic Reporting for period 1 - HESFIRE (Drivers and projections of global fire activity and intensity under future climate and societal changes.)

Reporting period: 2015-08-01 to 2017-07-31

The human population has more than doubled in the past 50 years, expanding the scale and diversity of environmental impacts from our activities. The build-up of greenhouse gases in the atmosphere, as well as the degradation and conversion of natural lands, have major consequences for future climate, natural ecosystems, and human societies. The interactions between human and natural systems are complex, yet observational data, field experiments, and various types of models continue to elucidate key linkages between climate variability, ecosystem function, and anthropogenic activities. This knowledge is essential to anticipate potential changes under future conditions and to design adaptation or mitigation strategies that promote the sustainability of the coupled Human-Earth system.

One of these interactive processes linking human activities and natural ecosystems is fire. The earth has been naturally affected by fires since terrestrial vegetation appeared on Earth, about 350-400M years ago. Fire has an important role in the functioning of ecosystems. As a disturbance agent, it promotes their regeneration, recycles the nutrients, and maintains biodiversity. Most forests would evolve towards mono-species stands of low productivity without fires, encouraging other disturbances such as widespread diseases.

Human activities now exert considerable influence over global fire activity, however, through fire practices for agriculture, deforestation, and with accidental/criminal ignitions. Natural fires – mostly due to lightning – now represent less than 5% of all fires. On average, fires burn an area equivalent to the size of India every year, thus altering fire regimes can have significant impact on the Earth System.

Fires are due to a combination of natural and human drivers converging towards fire-prone conditions. Significant wildfires are contingent on an ignition source, on the availability of fuel to burn, on low moisture conditions, and on un-fragmented landscapes to spread over large areas. The interaction among these drivers – including the deviation from natural fires due to human activities - is illustrated in a number of recent fire episodes. Devastating fires burned in tropical forests of the world due to the “El Niño” drought in 1997-1999, where human-ignited fires emitted an estimated 13 to 40% of the world’s annual fossil fuel emissions. In 2017, fires in Portugal resulting from poor forest management, agricultural abandonment and extreme weather conditions burned around 5% of the country and killed more than 100 people. Climate and societal scenarios suggest that ecosystems and society will be exposed to substantial changes in the coming decades, with a potential for increasing fire frequency and intensity.

In this context, improving our understanding of fire drivers and how they will affect future fire regimes is a critical question to evaluate the vulnerability of ecosystems and the efficiency of fire mitigation strategies. The HESFIRE project aimed to address this need with a multidisciplinary approach to a) tackle the lack of knowledge on fire activity & intensity drivers; b) integrate this knowledge to develop a new generation of fire models with realistic performances and extensive fire assessment capabilities; and c) apply this framework to infer future fire projections and guidance for the design of fire mitigation strategies. The specific objectives and the conclusions reached over the two years of the project were as follow:

1- Tackle the critical gap in our understanding of fire intensity drivers for fire modeling.


2- Explore fire regimes under a variety of future scenarios and generate decision support for environmental policies.


3- Foster the development of inter-disciplinary approaches to better account for interactions within the Human-Earth System.
The specific objectives and the conclusions reached over the two years of the project were as follow:

1- Tackle the critical gap in our understanding of fire intensity drivers for fire modeling.
Fire intensity - the heat of a fire – is essential to understand as it plays a major role on fire impacts: intense fires increase vegetation mortality and emissions, involve a long recovery process with opportunities for non-native species invasion, and hinder suppression efforts. The project highlighted the complexity of this fire aspect and the lack of observation data (e.g. density and structure of the vegetation) needed to perform proper statistical analysis for publication. Preliminary results however suggest that strong winds and drought conditions – likely to become more frequent in many regions of the world – are major drivers of high-intensity uncontrollable fires, which will only terminate with a change in weather conditions or when reaching a substantial fire breaks (e.g. large rivers).

2- Explore fire regimes under a variety of future scenarios and generate decision support for environmental policies.
The development of a fire model (HESFIRE) and its application to the Amazon region contributed new explicit knowledge on the drivers of fires. In particular, we quantified the relative importance of climate versus human activities as fire drivers. We concluded in a scientific paper that without a global, concerted effort to mitigate climate change, regional policies to limit fire frequency (e.g. reduced deforestation rates over the last decade) are and will be little effective.

3- Foster the development of inter-disciplinary approaches to better account for interactions within the Human-Earth System.
As mentioned before, fires are to be investigated as a transversal issue encompassing many components of the Earth System, including the dynamics of our society. Otherwise, decision-making may result in counter-productive results. As an example, policies established in the early 1900s to suppress fires in the U.S.A. have been very successful, promoting the growth of dense and unfragmented forests. Unforeseen at the time, however, these forests are now so dense that they burn with extreme intensity and are virtually uncontrollable, leading to so-called “mega-fires” with devastating impacts on ecosystems and communities. Anticipating such outcomes requires integrative tools such as Integrated Assessment Models (IAMs). This project had a strong emphasis towards such methodological developments and collaboration with the release of 3 open-source computer models to explore those interactions in the context of fires, deforestation, and agricultural food production, respectively.
Our understanding of the Earth System is improving and solutions to mitigate our impacts are obvious (e.g. reduce emissions). But many variables are involved, including very complex natural processes and equally unpredictable societal trajectories (e.g. the economy, policy-making). Future scenarios of environmental changes (e.g. warming, drying, fires) such as those produced in this project are not to be seen as accurate predictions of what will change where. Rather, they provide clear evidence that with the continuation of a heavily fossil-fuel dependent economy and mass-production/consumption society, the current equilibrium of the Earth System will not last. The project highlighted the need for new societal dynamics, and contributed knowledge and tools to help design forest management and agricultural strategies that improve sustainability.
Overview of the downscaling method
Downscaled cropland and forest projections in 2100 under two alternative mitigation policies