‘A little bit of everything is burning.’: A NASA scientist dissects Amazon fires

A rash of fires in the Brazilian Amazon has caused diplomatic tensions between Brazil and several European countries and triggered protests from environmental groups around the world. Brazil’s government has pledged to stop the fires and sent in the military but denies its policies and rhetoric are responsible.

Science talked with remote sensing specialist Douglas Morton, one of the scientists who is closely watching the blazes. Morton heads the Biospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, which monitors land use and environmental changes through satellite data. Between January and late August, NASA’s Terra and Aqua satellites have detected 100,000 “fire spots” in the Brazilian Amazon—the highest number in that period since 2010. The numbers are in line with those from Brazil’s National Institute for Space Research.

With partners at the University of California, Irvine, Vrije University in Amsterdam, and the University of Maryland in College Park, Morton maintains the Global Fire Emissions Database, which tracks carbon emissions and burned areas from fire activity around the world. He has also worked in the field with Brazilian colleagues since 2001, studying the forests’ vulnerability and resilience to drought, fire, and logging.

This interview has been edited for brevity and clarity.

Q: Is there a real reason for alarm at this point, or is the world overreacting to the fires in the Amazon?

A: I come to this situation with a sense of concern because this year’s patterns of deforestation and fire differ from the trajectory of the last dozen years when Brazil managed to keep deforestation at a level that’s far below the record years of the earlier part of this century. I don’t think we need to get to a point where fires and devastation grow to extreme levels to start a dialogue about what trajectory we want to be on.

Q: Not every fire spot represents an individual fire, right? What do the satellites actually see, and how do you interpret those data?

A: Essentially, what the satellite sees is an area of the planet that’s hotter than its neighbors. That thermal anomaly gets registered at the resolution of the satellite imagery—which varies depending on the instrument—and then we can use the number of thermal anomalies to compare years, using data from the same satellite sensor. A large fire will trigger many pixels in a satellite image as thermal anomalies, whereas an isolated detection may actually represent a combination of many small fires in the same location. The timing, location, and amount of energy released by the fire all provide information for scientists and fire managers.

Q: What role does climate play? Is drought or any other climate anomaly driving the increase in fire activity?

A: There are conditions this year that would make the region more vulnerable to drought, and we are on the lookout to see how those conditions will develop across the Amazon throughout the year.

Q: But nothing out of the ordinary is happening at this point?

A: The southern Amazon is dry every year, for several months, and so fires occur every year. However, we are seeing some patterns in 2019 that depart from the types of burning we’ve seen in the last decade. This year, so far, has been marked by economic drivers and increased fire activity in locations previously identified as deforestation; whereas widespread climatic risk typically synchronizes the entire landscape and makes everything more fire prone, from pastures to standing forests.

Q: How can you tell fire activity is linked to deforestation? Can you see that in the satellite images or do you need eyewitnesses on the ground?

A: There is some information we can take directly from the satellite measurements. We know the location and duration of the fires, and the amount of energy they produce gives us an indication of what is burning. We can see smoke plumes from intense fires rising higher into the atmosphere and spreading further downwind; and we see fires that are burning in the same location for multiple days, which is only possible if they are burning wood. Fires that are burning through grasses or agricultural fields will pass quickly and do not produce as much energy. So, we can look at all these characteristics together to identify burning that’s more consistent with deforestation than with other fire types.

Q: What’s your reading of the situation, based on your remote sensing expertise and field experience in Brazil?

A: My sense of things right now is that the fire season got off to a higher than usual start based on an increase in pressure for land clearing, and the use of fire as part of the deforestation process. I think this is a time to be vigilant, because we are only midway through the fire season across the southern and eastern Amazon, and the challenges will grow as more and more parts of the region participate in dry season burning. At this point, a little bit of everything is burning.

Q: What are the economic drivers that you mentioned?

A: Historically, the major producers in the Amazon have been ranchers looking to produce beef and leather, and farmers seeking to expand the production of soybeans and corn. It’s too early to determine what these new areas that have been cleared and burned will be used for. There are three steps in this process: We saw the increase in deforestation, now we are observing fires that are almost certainly associated with that deforestation, and in the coming months we’ll be able to use satellite data to identify if these areas are planted with crops or put into pasture for ranching cattle. So, I can’t tell you right now what the economic motivations are, but in 4 to 6 months we’ll have a much better picture of that.

Correction, 4 September 2019, 10:30 a.m.: A previous version of this story did not include the University of Maryland in College Park as a collaborator in the Global Fire Emissions Database.