Why is Harvard flying drones in the Amazon Rainforest?

I have one of the coolest jobs ever. I am a researcher at Harvard University and I fly drones in the Amazon Rainforest.

If man doesn’t learn to treat the oceans and the rainforest with respect, man will become extinct.Peter Benchley, American author

MUSA Tower in the Amazon Rainforest, close to the city of Manaus in the Amazonas region of Brazil. (Source)

I often get asked by people “why do we need drones in the Rainforest?” and the truth is, we don’t need them. There is nothing special in itself about flying drones in the Rainforest, the real need becomes apparent when we start to think about studying the atmosphere. If I want to measure what the atmosphere is made of and how it changes over space and time, what is the best way to do this? And why would I want to study what the atmosphere is made of?

Why study the atmosphere?

The field of environmental science is a relatively new one, it has only been around since the 1950s, which was kickstarted by some pretty bad events such as the Great Smog of London in 1952, whereby thousands of people died due to an environmental phenomenon which causes low-level air to become trapped and recirculate for several days. We have come a long way since those days and the modern world is relatively clean in comparison to the 1950s (although there is still a long road ahead in terms of climate change and other environmental challenges).

That being said, monitoring the atmosphere is still a crucial part of environmental research. Many important phenomena to do with the chemistry of our atmosphere are now well known, but there is still a lot more to learn. One of the key areas of research in atmospheric chemistry is the evolution of volatile organic compounds. For anyone familiar with chemistry, imagine the complexity of an organic chemistry class, combined with the fact that every one of these chemicals is so rare that we can only measure them in parts per billion, parts per trillion, and even parts per quadrillion. This may sound insignificant, but now consider that there are millions of these chemicals, with vastly different chemical structures. Now let me blow your mind, imagine that each of these millions of chemicals can react with each other and change form, and at varying rates, such that nothing stays constant. Now add the complexities of temperature and humidity, as well as a daily dose of sun, wind, trees emitting chemicals and producing oxygen, humans breathing, and industries and housing pumping out random chemicals from their smokestacks.

If I have not already blown your mind, now try to imagine things from my perspective. My research involves studying the chemicals that are emitted by the plants in the rainforest, and to learn how these chemicals react in the atmosphere and magically (quite literally, nobody understands how this process of homogeneous nucleation actually occurs) transform from gases into solid particles, called aerosols (this is a huge simplification of what actually goes on, but let us skip the nitty-gritty details). Aerosols are pretty important, they rise up in the atmosphere and at a certain height water condenses on them, like water condensing on a window, except in the sky the only surface is these tiny particles. This is how clouds form and clouds are pretty important for the Earth as a whole, they are fundamental to the water cycle, and they also regulate the amount of radiation that the Earth absorbs from the Sun. This nifty process is illustrated nicely below.

Illustration of the complex processes involved in gas-to-particle conversion and cloud formation. (Source)

To make this a bit less abstract and more at home, these chemicals exist everywhere in different quantities and produce aerosols that are less than one micron in diameter (that is 1000x smaller than a millimeter). These particles are so small that when humans breath they inhale many of these particles, particles which can penetrate so deeply into the lungs that once they are in your lungs they will never be able to escape. As you might suspect, having highly reactive aerosols in your lungs is not great for your health, and higher concentrations of these aerosols have been linked to higher occurrences of cancer, asthma, and respiratory diseases like COPD.

There is a famous study by the Harvard School of Public Health called the Six Cities Study, which showed that the air quality in 6 different cities had a direct correlation to life expectancy. Essentially, they showed that depending on where you choose to live you could be reducing your own life expectancy, in the extreme cases by several years. Efforts by the EPA have made most cities in the U.S. relatively safe in terms of air quality, but some cities like Beijing still have very high levels of particulate matter that are silently causing the premature deaths of millions of people. A staggering fact I read in a paper recently suggested that by reducing air pollution around the world to meet the standards set by the EPA could increase the average life expectancy of a human more than if we were able to cure every cancer in existence. That is quite a statement indeed.

Penetration of particulate matter of different sizes in the human respiratory system. (Source)

So we have made a good case for why we should care about studying the atmosphere. Firstly, we can save the world from premature death caused by air pollution and secondly, we can better understand the chemistry of the atmosphere and use this to combat climate change and help preserve the rainforest for future generations. Neither of these sound like trivial tasks, and there are millions of types of trees in the rainforest, there are entire books in fact, which describe each of these trees in detail. Given my predicament, how would you suggest I make meaningful measurements so that I can have some research to present at the end of my Ph.D.?

Drones as a platform for atmospheric measurements

To save you some thinking time, I already know the answer because this is my job. Traditionally, there were two ways to make atmospheric measurements:

  • Tower measurements
  • Airplane measurements

Tower measurements are great, I can lug a $1M analytical chemistry machine to a remote region of the Amazon Rainforest and I can sample air there and get decent measurements. There are a few downsides though, firstly, getting through customs with a 100kg device with things like lasers and pumps (fun fact, the word for ‘pump’ in Portuguese is actually the same as the word for ‘bomb’) is a nightmare, and the entire procedure usually takes several months to complete. Secondly, once the machine is in the right location I have very little flexibility in terms of moving it to a new location to make measurements. Even if this device lets me measure things in real time, that lack of portability means I have to assume the whole rainforest has the same properties as my one measurement location.

Airplane measurements may seem like a great idea then, why not just put one of these devices on a huge aircraft and fly around with it? It has been done, and there are many papers where people do this. The downside is that I can only measure one location for a fraction of a second before the plane flies past it. The high speed of the airplane also means that you can’t measure certain chemicals and your results might be distorted. This type of measurement is also super expensive, so it is prohibitive for most research.

Measurement methods used in atmospheric chemistry. (Source)

What then would be a healthy medium between these two extremes? Drones. Drones are not a million dollars, and as long as I can get a decent sensor to put on my drone that is not 100kg, I should get some decent results. The drone has several advantages but clearly, the main one is that I can fly and just sit at a location for as long as I want and then move on. If I have enough batteries, I can keep flying all day and get a lot of data. I can also take air samples and store them in tubes so that I can analyze them later. The only real downside to sampling with a drone is that the drone is not waterproof, which is not great during the wet season (when I was there it rained every day like clockwork at 2 pm). The drone we use is a DJI Matrice 600, it is huge and sounds like a small helicopter when it takes off. This is the same as the drones used in Hollywood to film movies, but we remove the camera and attach an air sampling system.

DJI Matrice 600. (Source)

It has become a fairly common occurrence in atmospheric chemistry now to use these drones to study the atmosphere, largely due to their versatility. There are a bunch of research groups that have published papers where drones have measured emissions over highways using drones, as well as in various forests and cities.

Here are some free materials that outline the procedures in more detail:

So why the Amazon Rainforest?

Good question, it is not immediately obvious why we would be interested in studying the Rainforest other than the fact it is the largest in the world. In terms of the organic (anything containing carbon) chemistry of the atmosphere, biogenic species — which are the organic chemicals that are produced naturally by things like plants — are the dominant emissions compared to anthropogenic emissions from devices like automobiles and airplanes. It has been shown from previous studies that around 2/3 of the world emissions of volatile organic compounds come from biogenic sources like the rainforest. The large biodiversity and climate also give the rainforest unique properties that are not well understood, and since it is the largest forest environment on Earth, we should probably try to understand how it works and how best to keep it alive and thriving. Plants emit chemicals in other to communicate with other plant species, but they also emit specific chemicals in response to environmental stresses such as increased temperatures, similar to the way humans sweat and give off odors when they are hot. Most of these processes are not well understood, and certainly, their collective behavior in response to changes in the environment such as increased temperature caused by climate change are not understood.

“The time has come to link ecology to economic and human development. When you have seen one ant, one bird, one tree, you have not seen them all. What is happening to the rainforests of Madagascar and Brazil will affect us all.”
Jamie Murphy and Andrea Dorfman, ‘The Quiet Apocalypse,’ Time (13 Oct 1986)

I want to know more!

If you are curious about this research or anything I have discussed, feel free to reach out to me on Twitter, @mrdragonbear, or on LinkedIn. There are also several online articles about our research, such as on ExpoUAV and on the Harvard website.

I will be writing more articles on this topic in the future in order to help introduce environmental science concepts and help people become more informed about their planet. Watch this space!

Myself (left) and colleagues from Harvard University and Amazonas State University preparing for their first drone flight at MUSA Tower, close to the Brazilian city of Manaus.

Matthew Stewart, PhD Researcher

Written by

Ph.D. student at Harvard University and part-time machine learning and blockchain consultant.

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