When was the last time you were so disoriented – if just for a moment – that it made you question the fundamental nature of space-time? The first time I experienced that was my first week of junior high, before I understood that the building (which was considerably larger than the elementary school I had attended) had two different sets of stairs. For the first day and a half, I struggled to understand why sometimes I arrived immediately at my new locker and between other classes I wandered through three hallways before finding it.
Arguably I have come a long way from that navigationally challenged twelve-year-old. I know how to use a topo map and a compass, and have even on occasion been entrusted with groups of small children out in the mountains. I think the fact that I keep bringing them back speaks well of my ability to get my bearings (eventually). And last August, I was ready to test those skills in one of the most challenging navigational situations on Earth: the Amazon rainforest.
For more on what I was doing in the Brazilian Amazon, you can skip to the section below, but to briefly set the scene, I had been there for about two weeks, and I was on my way to one specific individual tree about 600 meters (0.6 km) into the forest. I was not carrying a compass. Two intersecting trails could get me within 30 meters (90 feet) of the tree before I had to set off into the undergrowth on my own. The first trail, T2, is a straight line from the research base extending out for a full kilometer. Halfway down T2, it is intersected at a right angle by T4, another kilometer-long straight line. The route to the tree in question involved turning left onto T4, then after nearly 100 meters, striking off to the right into the forest:
I would find the point of departure from the trail using the PVC pipes marked with distance every 25 meters. I also had hiked to this tree several times in the last two days, so I had a vague memory of the lianas and fallen branches that marked the point.
Walking 30 meters from the trail would be straightforward in the desert or mountains, unless there were a cliff or an enormous cactus garden in the way. But in a dense forest like the Amazon, you can neither see your target nor where you came from. There are understory plants, lianas, fallen logs, and other hazards to throw you off course. Since I knew we had thrashed a bit of a break in the undergrowth over the past two days, and I also knew where to start from off the trail, I would just walk in a straight line from there to the tree, following those gaps.
However, another grad student who would be joining me shortly to climb the tree had only been to that particular tree once. He probably did not remember the exact place to leave the trail for easiest travel. So I scuffed a little mark on the ground with my toe. We would be within shouting distance, and I could tell him to look for that mark.
This time out, I was wearing a heavy backpack, full of climbing rope and rigging slings. I moved more awkwardly between the leaves, seeking larger gaps and snagging on thorns. I wasn’t sure I was following the same route I had before, but kept finding my way through gaps out toward the tree. I thought I recognized a downed log and went around it. I started to wonder if I had passed the right tree by then. Then suddenly, I stepped out onto a straight and well-beaten path where none should have been. I was stunned. Had I walked far enough and at enough of an angle to have arrived farther down T2? I looked left and right to see where the nearest meter marker might be. Then I looked down.
I was standing exactly on the scuff I had made before leaving T4. Somehow, without ever realizing it, I had walked a neat little circle, no more than 30 meters in diameter, and arrived exactly where I had started while thinking I was walking in an approximately straight line. I had heard of people walking in circles in forests, but pictured it happening to completely inexperienced hikers, maybe over the course of a few miles. Not to me, and not in so small a space.
Not long before I set out, another grad student there, Ty Taylor, had been talking about his strategy for navigating in the dense forest: get a sense for where the sun is, and walk straight relative to that. In other words, keep your head up, your focus on a higher objective, and avoid the trail-blindness trap of blundering into each next easiest vegetation gap.
The sun had been dodging to and fro behind clouds that afternoon, but, once my head stopped swimming, I turned around and got a good look at the angle of the shadows. I started walking toward my target tree, following the shadows, and not minding so much the snagging on vegetation. This time I walked straight to it.
I have kept thinking back to moment in the two months since, as I finish writing my dissertation. I like it for a number of reasons. Foremost was the profound wonder at understanding I had walked in a circle, laughing at the magic trick the forest had played on me, but also fairly awed at how completely I had been taken in. And of course there is also the physicality of the obvious metaphor: marching on with the heavy pack and trying again, where I had failed the first time – but this time maintaining perspective, context, and direction. Heading where I wanted to go, rather than focusing on finding the easy path that had been walked before.
For the curious: Why was I stalking a tree in the Amazon rainforest?
Last August, I spent several weeks helping with the Saleska lab’s research as part of an international collaboration in the Brazilian Amazon. The overall effort is broadly focused on predicting whether the largest carbon sink in the world will be able to absorb excess CO2 from the atmosphere, mitigating climate change, or whether it will die off and spew the carbon from decomposing wood into the air, which would accelerate climate change. One important piece of predicting whether a forest will die back or thrive under the potentially hotter and drier conditions is to know whether leaves can continue photosynthesizing. By measuring the water released by a leaf or the carbon dioxide taken up by a leaf, researchers can calculate their activity. But here’s the challenge (well, one of many challenges of doing research in the Amazon, really): conditions on the forest floor are pretty different than in the canopy. Sounds obvious, but it becomes important when you try to measure sensitive leaf behavior. So you have to get into the canopy.
Getting to the canopy means climbing up a tree anywhere from 20-50 meters. That’s about 60-150 feet! Rope systems are a must – if only because smooth, bare tree trunks are difficult to climb themselves, to say nothing of the risk of falling.
But if you are securing yourself to strong forks in the trunk, how do you safely work your way to the edge leaves that get the sun? Branches get thinner, and you are farther from your anchor point, meaning a longer fall and a nasty swing toward the trunk.
Professional arborists and experienced researchers can set up rope systems between multiple trees in a Tyrolean traverse to work their way out to a canopy in the middle, suspended by the ropes from other trees. But that is physically difficult, and can take several days to set up to sample a single canopy. Besides, where do you set your sensitive leaf-measuring equipment then while dangling there?
Solution: invest the time and expense to build platform walkways between some trees. And that is what they are doing, and what I helped with.
But once you spend the time and expense to build a small number of platforms, you want to make sure each one is really worth it – that it is safely built on large and healthy trees, with no big dead trees looming over it and ready to fall, and with multiple canopies of interesting species along the walkway.
It turns out these criteria are remarkably difficult to satisfy. After spending a day and a half searching about 25 meters to each side of an entire kilometer-long transect, I, along with an English arborist and a local forester had located only two potential sites. Part of the survey process involved sending the arborist up at least one tree in question to have a better look, which is why I had walked back and forth from the well-traveled T4 path to my target tree several times in two days.