Earth Warms, and Fires Rage
to clear forested land for farming or the grazing of livestock. In Brazil’s case, this is driven by a global demand for soybeans and cattle.
Between 2004 and 2012, deforestation in the region had been on the decline, but that changed in 2013. Jair Bolsonaro, who was elected Brazil’s president last year, has championed the expansion of the farming industry and has dismissed the idea of extending protections to indigenous groups that live in the forest, which has led to worries that deforestation rates could further increase.
Indigenous communities in the Amazon have used fire in the rainforests for generations, though they tend to cultivate much smaller areas, plant a relatively diverse number of crops and move onto a new plot of land after a few years, allowing the forest to regrow.
That is different from what is happening in the Amazon, where today’s more industrialized agriculture means that deforested land tends to remain permanently cleared.
A similar pattern is playing out in Southeast Asia, where 71 percent of peat forests have been lost across Sumatra and Borneo in Indonesia and peninsular Malaysia between 1990 and 2015. In many cases the forests were replaced by farms that produce palm oil, which is used in things like cookies and cologne.
Even though both involve the burning of peat, the fires in Indonesia are quite distinct from what is happening in the northern reaches of the globe, including the Arctic. This summer, wildfires broke out across the region — including Alaska, Greenland and Siberia — in places that have not typically burned in the past.
The fires are driven by rising temperatures, which dry out plants and make them more likely to ignite. Many researchers describe the heat as a signal of climate change in a region of the world that has warmed more quickly than the rest of the planet. This summer, parts of Alaska broke records: Anchorage reached a high of 32 degrees Celsius on July 4 when the average temperature for that date is 24 degrees.
The fires can also exacerbate warming because of the soot produced by burning peat, which is rich in carbon. When the soot settles on nearby glaciers, the ice absorbs the sun’s energy instead of reflecting it, speeding up the melting of the glaciers.
Not all wildfires are unexpected. In some places, there is a seasonal cycle of burning that plays a major role. The American West is one example.
It is true globally that humans trigger most wildfires, whether accidentally or intentionally. However, one reason places like California seemingly have wildfires every year is because the state, along with much of the West and Southeastern United States, has what researchers call a fire-adapted ecosystem.
In other words, some landscapes have evolved over time to not only tolerate fire, but actually need it. For instance, lodgepole pines, a staple tree of the Western United States, need the heat from wildfires to release their seeds.
A similar pattern can be seen in some of the sub-Saharan African fires that have recently drawn the world’s attention. According to Dr. Abatzoglou, the savanna ecosystems just north and south of Africa’s tropical rainforest burn fairly predictably every two to three years.
“This is really the most fire-prone ecosystem globally,” he said. “It’s the right combination of it being wet enough to have enough fuel and dry enough to burn.”