Working at 15,000 Feet, Greg Asner Is Still Firmly Rooted on Hawaiian Soil

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Clearly, Greg Asner would rather not talk about his 15 minutes of fame.

“It’s very embarrassing,” he says of his having been named by Popular Science magazine last October as one of its “brilliant 10” scientists and researchers of 2007.

“It just came out of the blue,” Asner said in a recent interview, “but if it draws attention to the problems we’re addressing, I guess that’s okay.”

And these days, what’s causing Asner to lose sleep are the many threats he sees to the survival of Hawai`i’s native forests.

Asner, a staff scientist with the Department of Global Ecology at the Carnegie Institution for Science, at Stanford University, and his team of about 10 scientists and technicians, conduct research around the globe. In mid-March, they flew to Kruger National Park in South Africa for several weeks as part of a multi-year study. In the past, the team has looked at ecological issues in the southwestern United States, the Amazon, and elsewhere.

Yet Hawai`i remains a special focus. After receiving a degree in aerospace engineering, Asner came to Hawai`i in the early 1990s. Here, he found work as a field technician with The Nature Conservancy, where he was introduced to the challenges of managing natural resources in the face of limited personnel and funds, on the one hand, and aggressive invaders, on the other.

After his stint with TNC, Asner returned to school, receiving graduate degrees in ecology and biogeochemistry from the University of Colorado. For the last decade, he has been developing ways to streamline the process of gathering detailed information about natural resources on a large scale. The culmination of those efforts is the Carnegie Airborne Observatory, Asner’s brainchild.

The observatory consists essentially of two instruments – one a Light Detection and Ranging (LiDAR) system that captures light reflected from up to 100,000 laser beams per second and which generates information on the physical characteristics of the landscape (forest canopy height, topography); the second is a high-powered spectrometer, analyzed by Robin Martin, Asner’s wife and team member, which can measure the reflected light and generate information on the chemical properties of whatever the light hits. By comparing the known chemical profiles of plants with the chemical signatures read by the spectrometer, it’s possible to identify what plants are in the forest below, and where they are – down to a single tree.

Asner and his team mount the observatory in a small twin-engine plane, with a viewing hole cut into its floor. Flying at a height of up to 15,000 feet, for the last year, they’ve been mapping Hawai`i’s forests, focusing on the Big Island, but with a few excursions to Kaua`i thrown in for good measure.

The observatory is the evolutionary result of many years of tweaking technology that most often was developed with altogether different applications in mind. “We started with cameras, and then began using the hyperspectral imaging and LiDAR combination in 2007,” Asner says. “The second-generation Carnegie Airborne Observatory is going to be in the works soon.”

“The whole process is based on increasing levels of technological mayhem,” Asner says, describing the madness behind his methods. “Hardware is hard, but ecology is even harder. Driving everything is ecology.”


“What is the sustainability of Hawai`i’s protected areas – against invasive species, land use changes, and climate change? How sustainable are these reserves?” he continued. “What is the efficacy of the work that is being done to protect them?”

Using the airborne observatory, Asner and his team are able in hours to generate answers to questions that it would take months or years to resolve with traditional ground-based surveys. The observatory can map 20 acres per second, at a resolution of 1 meter. With Asner’s maps, land managers can obtain near real-time information on what areas are vulnerable to invasion, where invasions are occurring, and where native forests are still intact.

Not that airborne surveys will replace old-fashioned field work. “We still need field measurements,” Asner says. “Even now, we spend more time in the forest than above it.

“But measuring some things on the ground is tough. Tree height, for example. That’s hard to do on the ground, but from the air, it’s a piece of cake.”

Also, it’s not yet possible to identify every species of weed from the air.

“The signatures of some species can vary,” Asner said. “Waiwi” – strawberry guava – “has a constant signature and is easy to map.

“Rubus, on the other hand” – blackberry – “has a variable signature, really variable. I think of it as sneaky. It can spread all over before it shows up in remote sensing. Morella faya is easy to spot, but Miconia is stealthy – until it gets to be a real problem.”

For these reasons and more, Asner said, “we’re careful not to oversell” the potential of airborne observing. “We’re still working on the science, in addition to management-related studies.”

It’s difficult work, with clouds playing havoc with scheduled surveys (the observatory needs clear skies). Conditions in the unpressurized aircraft require everyone aboard to wear oxygen masks. But Asner and the observatory are here for the long haul. The president of the Carnegie Institution has signed an agreement with the U.S. Forest Service, allowing the observatory to have office and lab space at the Hilo headquarters of the service’s Institute of Pacific Islands Forestry.

The observatory is collaborating with the state to map additional forest reserve areas on the Big Island. Recently, Asner and his team began working with Forest Service and Army staff at Pohakuloa Training Area as part of a Department of Defense restoration ecology project. “We’re trying to increase the extent and diversity of dry forest” in the Pohakuloa and Pu`u Wa`awa`a areas of the Big Island, Asner says. “We decided we could figure out where to do restoration work with the airborne observatory – mapping the woody plants, the fire fuel, topography.”

Although Asner’s work is still in its early stages, one thing has already become clear from his surveys: “The best forests we still see are surrounded by `a`a flows. As Rick Warshauer says, `a`a is the friend of the forest.”

— Patricia Tummons

Volume 18, Number 10 April 2008