- The research uses the chemical signals of tree communities to reveal their different survival strategies and identify priority areas for protection.
- Currently, the Carnegie Airborne Observatory’s airplane provides the only way to create these biodiversity maps. But the team is working to install the technology in an Earth-orbiting satellite.
- Once launched, the $200 million satellite would provide worldwide biodiversity mapping updated every month.
Sometimes for a scientist, the disconnected pieces of years of research come together in a single, “really awesome” point in time.
For ecologist Greg Asner, where it happened was about as important as the epiphany itself.
“I was almost on the Ecuador-Peru border, way up the Rio Tigre, and we had the moment,” said Asner, who heads the Carnegie Airborne Observatory (CAO) in Stanford, California. “We were days and days away from the rest of the world.”
It was the summer of 2015, and he and a pair of botanists had just connected the sampling they had done from CAO’s state-of-the-art research plane with their shoe-leather, on-the-ground observations of forests in the Peruvian Amazon.
They had measured the chemical signatures of different tree communities from high above. From those measurements, it seemed that the sea of uniform green they had flown over represented in reality an assortment of distinct growth and survival strategies.
At that moment near the Rio Tigre, they figured out that those unique community strategies – what they refer to as “functional diversity” – extended to an even finer scale, correlating with unique species compositions, or “biodiversity.” With that connection drawn, they’d locked on to a new tactic for identifying which areas are the most unique, the most diverse and, consequently, the most important to protect.
Their work in Peru, which they published in the journal Science on Thursday, is just the beginning: Asner now hopes to make the same measurements from space and map the biodiversity of the entire planet.
“The word ‘revolutionary’ is often overused, but I think this fits perfectly,” said Eric Dinerstein, a conservation biologist and director of biodiversity and wildlife solutions at the public policy organization Resolve, who was not involved in this research.
Peru is a country with 76 million hectares (293,438 square miles) of tropical forest, but threats such as big oil palm plantations, oil and gas extraction, and cattle ranching are driving that figure lower, as they are in many Amazonian countries.
Asner has a long-standing partnership with the Ministry of Environment in Peru, and he worked with ministry representatives on this study.
“They’re innovating,” Asner said of his collaborators in Peru. “They want to know if they’re protecting all of the different forest types that are out there.”
To answer that question, the research team employed a technique known as “airborne laser-guided imaging spectroscopy,” which they developed at CAO. By taking samples with imaging spectrometers mounted on the CAO aircraft, they can measure the different wavelengths of light reflected by the canopy as they fly over the forest, which in turn indicate the concentrations of certain chemicals present. The “imaging” part of this device adds three-dimensional pictures of the canopy’s structure.
The concentrations of a specific chemical – say, nitrogen, for example, which plays a critical role in photosynthesis – pointed to survival strategies, which varied from tree community to tree community. Asner and his team then distilled those strategies into seven community “traits” that had the most influence on the variations they were seeing in the forest canopy.
Now, the scientists could distinguish not just a handful but dozens of different types of forest. From that data, they then looked for classes that were well protected, and those that might be vulnerable.
Overall, about 40 percent of the country’s forests are protected in some way, either in a cordoned-off area such as a park or a reserve, or in some sort of sustainable use.
“More importantly, there are certain types of forest that are really underrepresented in the protected area network,” Asner said. Their work found, for example, that the tree communities at the base of the Andes are hemorrhaging 7,000 hectares (27 square miles) of forest a year in some places, due mostly to illegal gold mining and ranching.
Peru can take these discoveries and directly apply them to their conservation efforts, making sure that the full spectrum of the country’s rich habitats will endure.
But the possibilities for this methodology are in fact much bigger than just one study in a single country.
“We can use this piece of equipment, this sensor, to give us the finest-scale map of biodiversity ever created,” Dinerstein said. And that’s exactly what Asner wants to do – for the whole world.
“We need this map,” he said. “We need to go global.”
The trouble is, there’s only one plane like Asner’s. The technology is available nowhere else, limiting these sorts of analyses to locations where he and his team can get the plane and have enough time to survey an area.
But, Asner said, if they can install their instrumentation onto a satellite, they could produce these biodiversity maps for the whole world. What’s more, they’d be able to update them every 30 days.
The CAO team has been working with engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the technology is ready, he said. But it won’t come cheap. Currently, he’s building support for a project that would cost about $200 million.
That figure is still dwarfed by the $700 million price tag for a Landsat satellite. But most forest ecologists would argue that funding for the Landsat family has been well spent over the past 40 years. They’ve provided transformative revelations about forest cover that underpin tools like Global Forest Watch, and they allow us to keep an eye on what’s going on in the world’s forests in near-real time.
“If you think of our progress in understanding the status of forests around the world, it’s increased on an exponential scale,” Dinerstein said, referring to the work of remote sensing scientist Matt Hansen at the University of Maryland and others to map global forest cover.
Currently, the maps we get using data gathered from space are limited, without the resolution to tease apart the nuances that Asner’s team has revealed.
“Tropical forests are not homogenous,” he said. But right now, “any satellite view is just forest or not forest.”
A global map that lays out 36 classes – and perhaps more – of forest would open a window into insights beyond just the diversity of the trees in the canopy, he said.
Asner and his colleagues at CAO, led by postdoctoral fellow Mark Higgins, have already demonstrated that when the tree canopy is rich in species in the tropics, so are the plant communities that colonize the forest floor. Whether that diversity extends to the animal kingdom will require more research, Asner said, to unpack the “wonderfully complex” ecosystems in the Peruvian Amazon and in Borneo, where the group has done similar work recently.
Dinerstein said that these maps could tell us a lot about the largest group of animals alive today – the invertebrates.
“In many cases,” he said, “their life histories are tied to the plants they live on. If you could map plant diversity, you would not only have a rich database, but you have the most important proxy ever available for mapping invertebrates as well.”
Seeing the variation present in Peru’s forests led Asner and his colleagues to investigate whether something about these locations was instigating communities to evolve unique strategies for survival. They found that several factors play important roles, including the elevation, slope and climate of an area.
But one in particular stood out, and it turned out to be the foundation of the forests themselves.
“That geological patchwork underneath the forest has driven these species to become different,” Asner said. So now, in addition to the insights into biodiversity, the team’s new methods can pick out changes in the geology previously hidden beneath the forest.
That deeper understanding of how forests function and the array of differences that exist point to a need to change our approach to forest conservation, Asner said.
“We should be more tactical and more explicit about where we put protected areas,” he said. To his mind, it calls for an overhaul of the strategies we employ for protection “to maximize the number of species we try to save per acre or per hectare of land, rather than just putting down national parks wherever you can.”
“We have to deal with the fact that we have to feed more people and countries want to develop, so where do you put protected areas?” Asner added.
The monthly maps that Asner envisions would serve to bring a level of detail to the study of biodiversity that’s never been there before, and also provide a platform for discussion.
“It’ll get everybody to the same table about how to shepherd the biodiversity forward as best we can in this ‘sixth extinction‘ that we’re going through,” he said.
Right now, the expansion of this approach depends on one thing: getting the technology into to orbit. Asner has taken that challenge on with singular focus.
“I’m not going to rest until we get to orbit.”
Banner image of the Amazon landscape scarred by open pit gold mines in Peru by Rhett A. Butler
CITATIONS:
- Asner, G. P., Martin, R. E., Knapp, D. E., Tupayachi, R., Anderson, C. B., Sinca, F., … Llactayo, W. (2017). Airborne laser-guided imaging spectroscopy to map forest trait diversity and guide conservation. Science, 355(6323), 385 LP-389. Retrieved from http://science.sciencemag.org/content/355/6323/385.abstract
- Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. “High-Resolution Global Maps of 21st-Century Forest Cover Change.” Science 342 (15 November): 850–53. Data available on-line from:http://earthenginepartners.appspot.com/science-2013-global-forest. Accessed through Global Forest Watch on January 26, 2017. www.globalforestwatch.org
- Higgins, M. A., Asner, G. P., Anderson, C. B., Martin, R. E., Knapp, D. E., Tupayachi, R., … Alonso, A. (2015). Regional-Scale drivers of forest structure and function in northwestern Amazonia. PLoS ONE, 10(3), 1–19. https://doi.org/10.1371/journal.pone.0119887
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