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Planting networked sensors in the wilderness will help us understand ecosystems we want to protect.
September 1, 2001

Stopping over in phoenix on my way home to Boston a few years ago, I was treated to a rare desert sight: a storm roaring into the city.

The skies opened and rain began pouring down. Then, five minutes after the tempest started, the hotel’s lawn sprinkler system came on. Pretty dumb sprinklers. In a city like Phoenix you’d think the gardeners would be running around with Dixie cups to catch every precious drop. Maybe someday the sprinklers will at least be smart enough to check the Internet for a weather report before they start watering. Or maybe they’ll just ask the plants themselves.

I wish they could. When I got home to Boston, the plant in my office had withered into a desiccated, brownish heap. Unable to cry for help, incapable of reaching the keyboard to send me a desperate e-mail, neglected and ignored by the graduate students and custodians who occasionally peeked in to see if I’d returned, the poor Spathiphyllum floribundum (a.k.a. indestructible generic office plant) really looked like it was pushing up daisies.

Somehow, even with my black thumb, I nursed it back to health with a combination of Poland Spring water and Peter’s Plant Food. But it really irked me that, in this day and age of imported strawberries and bioengineered corn, my poor office plant was forced to sit in a clay pot full of dirt with no means of support whenever I had to be away, doomed to wither and die without a plant-sitter at hand.

When I complained to the graduate students about their shameless neglect of a dying soul, their immediate response was to construct an automatic plant-caretaking system. Called Robocrop, it was designed to use a handful of sensors to monitor growth and dispense light, water and nutrients. Aside from how to prevent office ecological disasters, the questions were: What’s the optimal cycling of resources to promote plant growth? Would it be better to simply leave the grow-lights on 24 hours a day, or to cycle them? Should the light sources move (like the sun) or just remain overhead? Could a time-lapse camera watch and measure the plant’s response to various stimuli? Does playing Mozart really grow the biggest tomatoes, or could the students systematically put Napster to work to hone in on the absolute best music for tomato production?

Often the cycles of a busy life make it impossible to properly care for plants. And just as often, your own instincts about when to water or supply plant food may not be in tune with the plant’s true needs. So perhaps a little Internet-controlled herbal garden, with a sensor network and computer-driven drip-watering and misting system could keep a supply of basil and other cooking plants fresh and healthy and at hand. I often think that such a system would make a nice addition to, say, Hewlett-Packard’s catalogue of scanners and printers. Maybe someday little packets of seeds will be hanging next to the ink-jet cartridges at CompUSA.

There is a real opportunity and need to better connect with the lives of plants, and it isn’t only about keeping your office lily alive, or about applying “green” techniques to your lawn. There are larger ecosystem issues that need a more vigorous systems approach. For example, climate change and the coevolution of various species are clearly critical issues, but in some respects we know about as much about those issues as we do about our own backyards, which is to say, not much. 

A few years ago, MIT students Matt Reynolds and Rich Fletcher were inspired by an expedition to Mount Everest to construct a device to measure the weather there. They built a bombproof (and Everest-proof) weather sensor in a plastic pipe and bolted it to the mountain, where it recorded the data for nearly a year and transmitted the results via satellite onto the Internet.   Conveniently, National Oceanic and Atmospheric Administration satellites swing overhead about ten times a day. It’s a store-and-forward system: the probe tosses up a 32-byte payload (enough for a couple hours of weather samples), and that packet blinks off the satellite and onto the Internet. At base camp, support teams can radio the climbers at higher-elevation camps (“It’s calm and sunny on the summit-now go for it!”).

Even the Weather Channel got interested enough to fund a few such probes (“It’s 79 degrees in Boston, partly cloudy, andthis just in, folks: the live weather from Mount Everest is”). This work is still at the stage in which computer engineers are probably learning more than ecoscientists, but it’s a valuable start.

More recently, a team of ecologists from the University of Hawaii was introduced to engineers at MIT. The group’s tactical mission: gather information about the extremely rare Silene hawaiiensis, a plant that lives in the southwest rift zone of the Halemaumau crater amid the volcanoes on the big island of Hawaii.

Island ecosystems are known for the starkly drawn lines between species. This is why Darwin discovered a living laboratory in the Galpagos, and why Alfred Russel Wallace was bowled over by the Indonesian archipelago. The island of Hawaii is home to a number of intriguing species, including curiosities like thornless berries and nettleless nettles: plants that enjoyed the paradise so much that they relaxed their natural defenses. In recent decades, though, Hawaii has become an ecological battlefield as alien species invade and disrupt the old balance.

Fieldwork for this project began on the northeast shore of Hawaii, in Hilo, the United States’ rainiest city. But a 50-kilometer drive southwest to Hawaii Volcanoes National Park brings you into a desert microclimate. Going from rain forest to desert in the space of a few kilometers makes this one of the world’s more sharply delineated climate zones.

There, around the ash-crusted rim of the massive Kilauea caldera, a few hundred scrappy little Silene plants are growing. They’re an endemic species, and not much is known about them. We don’t know how they pollinate, and we don’t really have a handle on the very particular climate in the area in which they’re growing.

Not too far from the Silene, you’ll find another extremely rare plant, the Portulaca sclerocarpa. There are perhaps only a hundred of these on earth, and they grow in one tiny patch in a place called Puhimau. What’s especially interesting about their little grubstake is that if you walk a few hundred meters away from the Portulaca and stick a thermometer five or six centimeters into the ground, the temperature reads 85 C. And when you look around, you see the charred remains of a forest. What’s happening is that an underground lava flow is heating the soil, killing the plants above, and it could easily wipe out the precarious Portulaca patch.

These sorts of phenomena require time-lapse logic, and time-lapse thinking. Because we’re in a wilderness within a national park, any instrumentation needs to be autonomous and wireless and very unobtrusive. So the combined MIT and Hawaiian teams came up with a novel approach. Students Andy Wheeler, Roshan Baliga, Ben Brown and Paul Pham built a tiny computerized climate sensor to measure light, temperature, humidity and wind speed. The nodes look like eight-by-eight-by-three-centimeter blocks, and they have radio links designed to self-aggregate into a wireless network. By sprinkling enough of these in an area, you can blanket a critical piece of territory with all the sensing required to form a much more detailed picture of what’s going on ecologically. And with clever camouflage that looks like logs and rocks, the sensors blend into the ecosystem.

Biology professor Mike Huddleston, associate professor of botany Kim Bridges, and their team at the University of Hawaii built some remarkable faux rocks and logs to hold the assorted electronics. In principle, a scientist simply walks out from the observatory with a bag of these high-tech rocks and drops one every 15 meters or so to form a daisy chain that leads out to the nearby Silene patch. The rocks look uncannily like the local chunks of tephra that are blasted out of volcanoes, and that’s how this first tephranet got its name. If it works, it should run for several months, producing the first intimate data snapshot of this extraordinary ecosystem.

Lush plants are a healthy part of life. Whether it’s a happy plant on the office window ledge, or a deeper understanding of how the last few members of a species are clinging to life, directing new capillary sensor networks into ecosystems can bring us real insight into problems that matter. Maybe the idea of a joint venture between Hewlett- Packard and seed giant Burpee seems a little far-fetched. But when I saw MIT student Andy Wheeler with his laptop walk over to an unsuspecting pumice rock and log into it via the tephranet radio, it was as if he’d opened a door to a new world.

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