Adventures in Self-Experimentation: Matrix Pills & Plowing Tropical Fields

Sometimes, science requires that you get dirty. And hot. Really hot. As graduate students, we never imagined that climate change research would lead to us plowing a rural Indonesian farm field in 96 degree Fahrenheit heat, topped off with 98 percent humidity. But here we were.

And 10 minutes earlier, we had each swallowed a high-tech temperature sensor pill, like something out of The Matrix.

Can Forests Help Keep Us Cool?

It all started with a simple idea: deforestation might lead to hotter local temperatures, which might increase the risk of heat illness in communities living in or around those forests. It seemed obvious to us that cutting down trees — which provide shade and can cool local temperatures via evaporation and transpiration — may lead to hotter microclimates and in turn impact people.

But when we reviewed the peer-reviewed literature, there wasn’t a lot of evidence for these links. This gap raised several questions about how people living in rural developing countries might adapt to temperature increases driven by deforestation and by climate change. We also wondered whether human alteration of the environment that exacerbates or accelerates these temperature increases would impact people’s livelihoods and daily lives.

So, we set out to explore whether there is any plausible link between deforestation, local temperatures, and heat illness risk. But we were new to this area of research and had loads of questions about the best ways to measure temperature, heat illness risk, and productivity. Our collaborators at the University of Washington School of Public Health introduced us to the many high-tech tools for gathering these data, which all involve advanced sensors.

Enter the Matrix pills.

The average human core body temperature should be around 98.6 degrees Fahrenheit, but that can vary from person to person. We needed a way to gather continuous measurements, so we could track how core body temperature changes during physical activity under changing external conditions. And the classic oral thermometer wouldn’t work, because it’s is infeasible and disruptive to stop someone every minute to take their oral temperatures.

Then we learned about a high-tech way to measure core body temperature: the CorTemp Sensor pill. When swallowed, these vitamin-sized pills measure core body temperature every 10 seconds, and then wirelessly transmit that reading to a data logger that is worn on the hip. But how well did they work?

Adventures in Self-Experimentation

Six months later we were standing in the middle of Long Duhung village, sweating profusely, holding the CorTemp pills in our hands. When it came time to actually swallow them, they were big but went down easily.

We had come to Berau, in Indonesia’s East Kalimantan province, to start scoping out our plan for field research. And so it was time to swallow the pills. We also strapped on heart rate monitors to measure physical exertion, and high-tech pedometers that measured the movement of our bodies along three axes as we worked. Lastly, we set up two sensors to measure the air temperature as we worked: an ambient temperature sensor and a Wet Bulb Globe Temperature (WBGT) sensor, which accounts for both solar radiation and humidity.

Then we grabbed two hoes, and set out to see just how hard it was to work outside in the sun in the non-forested tropics.

Walking to the edge of the village, we offered to help a local community member plow her field. She kindly accepted our help, and brought along a small crowd of friends to watch us — from a shady, relatively cool spot under the trees. Apparently, we were the day’s entertainment.

It was hot — the humidity enveloped us like a heavy, sodden blanket and the sun beat down on our heads. We deliberately decided to work outside at solar noon, the hottest time of day when the sun is at its highest point in the sky. And we were quickly regretting that decision.

We wore hats to get some shade, but we found ourselves taking breaks and slowing down. Our hands, better suited to typing furiously on our keyboards, were blistered and raw within 15 minutes. Our clothes hung heavy with sweat, and we had to grip the plows tighter so we wouldn’t lose control with our damp hands. The repetitive motion — raising the hoe up, swinging it down into the dry soil, and lifting the soil to create raised beds — was both mentally and physically exhausting after 30 minutes. The tracker on our wrist and waist logged every exhausted swing. And despite our best efforts, we could hear amused muttering from the audience as they relaxed in comfort under nearby trees.

After about an hour we took a break and sat in the shade with local community members. The trees really did provide cooling services — the shade felt at least 5 degrees cooler than the fields. While active we didn’t feel an urgent need to drink water, but once we stopped we both guzzled all the water we could get our hands on. In all, we only plowed two rows in a field that could fit about 15, a small fraction of a normal day’s work for these villagers.

This ad-hoc self experiment taught us a few lessons. First, mechanical farming equipment is hands-down the best invention of the past century. Second, while we have all worked or exercised out in the sun during the hottest time of day, the conditions in the tropics were a whole new level of hot. And the data we gathered backed up just how drained we felt.

For most people, having a core body temperature over 101.3 degrees Fahrenheit puts them at risk of heat illness, and the longer they’re over that threshold the more they are at risk. We started working at around 1pm, and within half an hour, both our core body temperatures were well over 101.3. And our core body temperature continued to rise even after a short water break.

Our heart rate increased rapidly above our resting heart rate, which was around 60 and 80 beats per minute for Masuda and Wolff, respectively. We also saw our movement slow down with time.

The kicker? We only worked for an hour.

The kicker? We only worked for an hour.

The bottom line is that outdoor manual labor in the tropics is difficult, and in our own personal experience it is plausible for people who work long hours in the tropics in the sun to be at risk of both heat illness and decreased productivity.

This experience helped us refine our questions about how forests and climate change can impact local communities, their health, and their livelihoods. Will people adjust the number of hours they work, when they work, or the activities they engage in as temperatures increase? If forests cool surrounding areas, how large and dense should the patch of forest be to provide a noticeable cooling effect? Can better landscape design help people adapt to climate change?

The questions we’re exploring are relevant for some of the world’s most vulnerable populations, and they have to be answered if we are to find sustainable and natural methods to adapt to climate change. In the short-term, the cooling services provided by trees may be critical for the health and livelihoods of these communities. Hopefully we’ll be back in Indonesia soon to advance our understanding of how forests, work, and health are linked in hot, humid, tropical climates.

But I don’t think they’re going to let us work the fields again. And we really don’t mind.