Sustainable fires become rare
Controlled fires are becoming increasingly rare - and difficult-to-control forest and bush fires more frequent at the same time. Is this related?
Forest and bush fires usually hit the headlines as catastrophic events, for example when settlements have to be evacuated or the tourism income of a popular vacation region is threatened. Yet fire has always been part of many ecosystems. Naturally flaring fires, for example after lightning strikes, have shaped prairie landscapes and forests and ensure regular regeneration of the habitat. And humans have also intervened for millennia, creating sustainable forms of land use with limited, controlled small-scale fires. However, it is difficult to estimate the global impact that humans have had and continue to have today. A British research team has now made an attempt. It concludes that controlled small fires are gradually becoming rarer worldwide. This, along with changes in ecosystems and climate change, may make it easier for large fires to occur in the future.
The team led by Jayalaxshmi Mistry of Imperial College in London tapped into an open-source global database of fire events, the Livelihood Fire Database (LIFE), for their analysis. It lists the circumstances of more than 1700 small fires and blazes intentionally set in different regions of the world, as well as the practice of setting fires, fire control, and the social and cultural backgrounds of this method. In many cases, the database demonstrates that controlled fire is an essential livelihood for many small-scale self-supporters and does not cause lasting damage to ecosystems.
This has remained important over the past 30 years, as the database analysis of fires from 84 countries around the world shows. The reasons for controlled small fires are many and varied. They can be used to create space for pasture or new crops, such as for rice farmers along the Indus and Ganges rivers or for cashew plantations in Guinea-Bissau. Setting fires, however, serves many other purposes. The Chiquitano in Bolivia burn ground vegetation because poisonous snakes hide there; Indonesian tribes set fires to keep away attacking wild bees with the smoke; and the Métis in Canada burn dead grass around their houses for aesthetic considerations. It grows back greener and fuller afterwards.
Overall, however, the number of controlled small fires has been steadily declining over the past three decades, write the authors of the study, which appeared in the journal Nature Sustainability. This is very often due to economic reasons that alienate small subsistence farmers from their traditional way of life. Land grabbing and displacement, for example, often ensure that people's living space becomes smaller. Occasionally, the opposite can also be true: Cashew farmers, for example, tend to cultivate larger areas of land today because their product yields more profit. However, fires are now set less frequently on the larger areas because the traditional approach would be too time-consuming. In addition, legislation plays a role. Often - especially in former European colonies - small fires are still banned across the board by the state. In doing so, the legislation follows a notion of fire ecology that had historically developed in the bioclimatic conditions of Central Europe, where fire was truly dangerous in intensively managed forests.
Overall, the trend toward gradually suppressed small-scale fire practices is worrisome, the authors write. It could be that the overall biodiversity of ecosystems that have been shaped by fire over thousands of years is declining. In addition, subsistence farmers often - though not always - lose their source of income, and many people's cultural identity is also threatened when their traditional way of life is curtailed. The abandonment of controlled small fires could then lead to large fires destroying rampant vegetation in an uncontrolled manner - with drastic consequences for ecosystems and people.
Spectrum of Science
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