The Mood of the Forest

The Amazon is getting mood-swings. And that’s where the drones come in.

The Mood of the Forest

The Amazon is getting mood-swings. And that’s where the drones come in.

You shield your eyes from the carnage that is now Earth. Your oxygen tank marks you as one of the lucky few to be blessed with the precious resource. What used to be a thriving jungle, rich in unexplored parts, and diverse in species, is now reduced to charred wood and black smoke, before your very eyes. Seems too horrible to be true, right? Well, maybe not.

It goes without saying that the Amazon is extremely vital to our existence on Earth. What with absorbing 5% of annual carbon emissions that seem to be only climbing up, the Amazon is necessary for the survival of more than a few. One in ten of the world’s species population, and about 390 billion—yes, billion—trees reside in this sweltering, massive rainforest. For context, there are only around a 100 billion trees in the entirety of China.

Oddly enough, that is precisely the reason scientists have started worrying about it. If the Amazon gets altered in any way, it may end up doing as much harm as it now does good.


Brazil started the rainforest’s deforestation in the late 1960s, due to the expanding cattle ranching and soybean industries. Logging is also a crucial factor, no doubt, but all the evidence points towards the former.

You see, the cattle ranching industry profits from the beef exports they make. The largest exporters in Brazil are Minerva, JBS and Marfrig. Ok, not the most popular names, but here are some you will recognize: McDonalds and Burger King. These and other fast-food chains have continuously bought beef from the Brazilian companies . Due to the immense profits that US companies piled up onto this business, cattle ranching has continued to expand. This has ultimately reduced a fifth of what the mighty Amazon was 50 years ago.

Tree cover aside, there has also been a raging increase in wildfires, according to Brazil’s National Institute for Space Research (INPE). Thanks to the rise of global warming, droughts have been alarmingly frequent, giving way to perfect conditions for wildfires to spawn.


Did I say ‘wild’ fires? That doesn’t even cover everything: man made fires are all the rage as well. With the rise of the aforementioned cattle ranching, farmers have been using what is called ‘slash-and-burn agriculture’. The idea is very simple: clear away all the trees from an area of forest, and burn the remaining vegetation to a crisp. Just like that, you have a whole new and fertile field to cultivate, pra caramba!

While slash-and-burn gets you started very quickly, it isn’t really practical in the long run. There’s the destructive deforestation, of course, but also the fact that while this technique boosts the soil’s fertility rate, that fertility is very short lived. Burning doesn’t bring in more nutrients; it's more like using up all the available nutrients at once rather than storing your usage to use it over the long-term—or in financial terms, blowing up your funds instead of saving. This forces farmers to move to a new plot of land when nutrients run out, and start all over again.

Thus, the circle of destruction continues. It’s really only a matter of time before the Amazon becomes what the Pridelands were, after Scar took over. A 2019 report by the INPE showed an estimated 80% increase in wildfires from the previous year alone.

And let’s not even get started on the increase of greenhouse gases that is causing the infamous climate change we’re always hearing about. If all this deforestation and increase of fires continues, immense amounts of carbon dioxide will be released.


Scot Martin, a Professor of Environmental Science and Engineering says, “Climate change, as well as human-caused deforestation and biomass burning, can lead to ecological and climatic tipping points that could release massive pools of stored carbon”. Trees and vegetation are what are keeping carbon dioxide trapped inside their bodies: if the trees die, all that carbon dioxide will go rushing back out into the already overcrowded atmosphere. Once a certain amount has been released—the tipping point, as it were—weather conditions will make the trees more vulnerable, causing them to die more easily, prompting the cycle to accelerate faster and faster.

This is precisely why a group of Harvard researchers are focusing their attention, putting in resources, and have taken some innovative measures...to detect when this dreaded tipping point could occur.

Hoping that they would have had a solution instead? Me too. But perhaps if we know how close we are to tipping points, it will help nudge people into working out the ‘why’s and ‘how’s to stop it.

But that’s for the future. Right now, researches seem to be more interested in finding out ‘when’. They do that by collecting what are known as Volatile Organic Compounds, or VOCs. These are chemical signals that are emitted by all fauna through their pores. They’re kind of like the pheromones mammals have—yes, including us—except with a less gross name. We’re not strangers to VOCs, that is what you smell when the lawn was just mowed.

So now you know how to distinguish between an overgrown lawn and a freshly mowed one. But VOCs can actually get much more specific than that.


In his play Pygmalion, George Bernard Shaw talks about how English varies with place. “Simply phonetics. The science of speech. That's my profession; also my hobby. Happy is the man who can make a living by his hobby!”

So says Professor Higgins, one of the main characters in the play. “You can spot an Irishman or a Yorkshireman by his brogue,” he continues, referring to a distinctive style of shoes people wear. But by listening to their language, “I can place any man within six miles. I can place him within two miles in London. Sometimes within two streets.”

While that may be an exaggeration, the English language does vary a lot with place, especially in England. There are hundreds of different dialects, and if you know them well, you can make out which area a person is coming from.

The VOCs of plants work like English words too—after all, they’re both used for communication, but each species and locality has a different variation. VOCs also vary depending on the ecosystem they’re in, making them further specific. And they become even more distinctive, because they are always changing depending on what the plant is feeling.

It’s like a fingerprint: no two plants will have the same set of VOCs, or, if they do, it'll be an extremely rare occurrence.


Remember how your science teacher said that plants are living things too? Well, they were right. VOCs can tell you a lot about the mood of a plant. Whenever a plant reacts differently to its environment, it releases a different kind. Some VOCs are used to attract pollinators, while others defend against insects and parasites. You know the fragrance you get when you smell a flower? That’s VOCs in action for you!

Flowers pollinated by insects have more VOCs than flowers pollinated by wind, so we know there’s something going on there. But the use of these compounds goes even deeper: VOCs are what help determine the phyllosphere of the plant. Confused about what that is? I was, too, until I compared it with the word biosphere—the collection of all creatures living in an area. The phyllosphere is everything living on the above-ground part—that is, the leaves, stem and bark, though not the roots. The term phyllo means ‘leaf’, so that makes sense in a way. Like us, a plant has hundreds of microorganisms living on and inside it, and VOCs decide exactly which microorganisms get there.

As you can see, VOCs are always being emitted by something or the other, and for anything able to sense them, they should be a familiar occurrence by now. The times we live in, however, are seeing a different kind of VOC, caused by the different kinds of mood that now come down upon the plants. Take the rubber tree Hevea brasiliensis, emitting a certain type of a VOC on a sunny morning.

All of a sudden that might change, if a tree next to it, say, spontaneously catches on fire.


Okay, so let’s recap. The Amazon, which might be a secret weapon against humanity in the works, is having mood swings because of climate change. We want to know how the Amazon deals with these mood swings. But how exactly are we supposed to detect these invisible signals?

Scientists want to know what kind of VOCs are released by trees when there is climate change, as a first step to figuring out what to do about the problem.

As the subtitle suggests, drones are being employed to do the work. This is mainly because they can hover, and have the ability to cover wide ranges—unlike airplanes or towers, which can only do one or the other. When they hover over a specific area, they can collect more data on that location, unlike airplanes that simply whiz past the trees. These drones are meant to fly over the Amazon with special drone-based VOC sensors developed by Daniel Wang, a student at Harvard.

The process is simple: there is a small box affixed to each drone that pulls in air from the nearby environment, and sends it through sampling tubes, which then engage the VOC particles.

Scott Martin—the environmental professor we met earlier—says that, “What makes drone-based sensors so exciting is that they offer the possibility of collecting data at unexplored scales”.

The first test was a complete success: the drone was able to get data from specific coordinates, and from a variety of altitudes. The group is currently testing these drones out in a variety of ecosystems. Students back at Harvard are also creating new prototypes of the drones, with improved technology. They will be tested out during the different seasons, to see how the VOCs change.

These people may not have exactly found a solution for the continuing climate crisis, but at least we’re getting there.


The INPE reported that the deforestation in the Brazilian Amazon during September 2020 went down by 34% compared to September 2019.

With so many schools putting a special focus on global warming, future generations are more likely to take a stand. So yes, we are trying to maintain our wayward footsteps on the right path. That accounts for something, at least.

And perhaps, if we stay on this path, we might eventually get a permanent solution for our future generations. The sooner we grow up, the better—but until then, let’s keep planting!

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