Steve Mirsky:    Welcome to Scientific American's Science Talk posted on March 20th, 2015. I am Steve Mirsky. On this episode:

José Iriarte:       These forests are rich in useful species, like tree fruits and palms, and we want to see if this is a legacy of past human modification.

Mirsky:      That's José Iriarte, he's an archaeologist at the University of Exeter in the U.K. and he's involved in a project to understand human activity in and influence on the Amazon region going back some 13,000 years. He gave a talk about the subject in February at the annual meeting of the American Association for the Advancement of Science in San Jose, after which frequent 60-Second Science podcast contributor Cynthia Graber talked to him about his work. You'll hear Iriarte mention LiDAR; the word comes from the combination of "light" and "radar" and refers to a remote sensing technology; you shine a laser onto a target and then use the light reflected back to create an image and measure distance. So that's LiDAR. And here are Cynthia Graber and José Iriarte.

Cynthia Graber:         Your research is looking at the issue of human influence in the Amazon. So what's the question there that scientists are trying to understand?

Iriarte:      The main general questions that we are trying to understand that today is a very controversial topic in archaeology, paleontology, and conservation is was the Amazonia a pristine, primeval untouched forest that was inhabited by a small balance of hunter gatherers, or shifting horticulturists that have a minimum negligible impact on the environment, and what's on the hand, Amazon inhabited by large, numerous complex and even hierarchy kind of societies that completely transform the environment. This is obviously the big overall questions.

Obviously Amazonia has been populating for the last 13,000. And Amazonia is a large place, larger than Europe. So now when we try to understand the nature and the scale of past human impact on Amazonia we need to go to the different regions of Amazonia that have different types of vegetation, for example, to answer these questions.

Graber:     So I read 1491 by Charles Mann and I was kind of blown away by that side of research in the book. And it seemed to me after I read the book I had this understanding that there was a huge human impact and that the Amazon actually is very highly manipulated. But you're saying that we don't quite understand what the level of human manipulation is.

Iriarte:      Yes, exactly. I think what the book of Charles Mann was incredibly opening our eyes to the human manipulation in past environment and important to question the long-held traditional paradigm of the novel savages possibly adapting to the environment. Now I guess we need to move forward and start studying these past human impact in different regions of the Amazon. What we are doing with this project that is founded by the European Research Council is an international interdisciplinary project that integrates different disciplines; it integrates archaeology, paleontology, botany, remote sensing, and soil science, because it's only combining the social or humanities with the natural sciences that we are going to have like a full understanding of the origins of these landscape.

In the past, and I'm talking in general terms, we have on the one side most of my colleagues, the paleontologists, working just on vegetation history, not paying too much attention of the past human impact on the environment, especially seeing as Amazonia was people all colonized at least 13,000 years ago. On the other hand, we have many of my colleagues, the archaeologists, not paying too much attention to how were the landscapes before. So what we are trying to do now is to, just to give you an example of some of the techniques that have been more productive is just looking at the archaeological sites with the classical archaeological techniques, and looking nearby for bogs or lakes where we can extract a sediment core and from there analyze the pollen, the charcoal, and try to reconstruct the vegetation _____ history. By comparing the culture and sequence from the archaeological sites with the paleontological sequence from the lakes or bogs, we can explore human environment interactions.

Graber:     You just said that it's larger than Europe. So how are you trying to get this big picture sense of how extensive human manipulation of the environment was in these kind of hierarchical societies?

Iriarte:      Well, I'm very lucky to be collaborating with Dr. Denise Schaan from Federal University of the State of Para, who has different projects along the Amazon. So our idea is to tackle four regions in the Amazon: the lower Amazon that is known for these Amazonia dark earth, that is arguably the most conspicuous signature of human manipulation and transformation of the environment. After that we are going to go to the middle Amazon, in the interfluves of the middle puddles and _____ rivers, where the work of the _______ ______ group of the _____ _____ National Institute of Amazonian Research has shown that these forests are rich in useful species like tree fruits and palms, and we want to see if this is a legacy of past human modification. Then we are going to go to southwestern Amazonia, where we have a seasonal forest; it has a very long dry season that is for a month, where we have been recently there has been discovered more than 450 geoglyphs in this area that were supposed to be like a pristine area with _______, evergreen forests. And then we are going to go to the seasonally ____savannas of the Bolivian Amazon in the Amazon _____.

In this way obviously the Amazon is huge and we are not going to be able to cover all of it, but in this way we are covering four regions with different vegetation and different past land use in pre-Columbian times.

Graber:     You mentioned this dark earth, which I find really interesting. How is that a very clear signature of human intervention?

Iriarte:      Well, most of the soils in Amazonia are the typical red leached soils that are completely infertile. It started mainly about 3,000 years before the present, the pre-Columbian groups that live in Amazonia start to settle down along the major rivers and just basically by the accumulation of trash, the accumulation of garbage, this soil has become much more enriched. And still today the soils today are completely fertile and are in big contrast with the typical interfluvial leached soils.

Graber:     Do you use any drone work or airplane flights or any type of LiDAR to get kind of a big picture sense? Is there any way to do something like that in a region like the Amazon, or do you really need to be kind of deep on the ground, doing these soil samples you're talking about?

Iriarte:      Well, we are doing both. But one of the innovative aspects of this project is to put together a UAV, unmanned aerial vehicle that has a laser sensor that is basically to mount a cloud scanner on top of this drone and spectral cameras. The advantage of this UAV with a laser mounted on it is that by flying this UAV above the forest we can do a topography of the canopy, but also we can look at the ground. The specialists of the project, that is Dr. Simon Carn, is a remote-sensing specialist, is able to perform vegetation removal algorithms that allow us to see only the laser beams that go to the ground and just make a fine topography of the ground. This is going to – it's already revolutionizing Mayan archaeology; obviously he's going to revolutionize Amazonian archaeology.

To give you an idea to look at some of the geoglyphs that I've been presenting and to make a complete topography of them in the forest may take a month with a team of at least 10 to 20 people, just making transits and cutting treadways in the middle of the forest. These now with LiDAR technology can be mapped in the morning, just flying the plane over it. There are large tracts of Amazonia that are completely unknown, so this LiDAR technology really is going to reveal what is below the forest.

Graber:     These geoglyphs, can you describe them? What are they?

Iriarte:      The geoglyphs are – the so-called geoglyphs are geometrically patterned earthworks. These are massive earthworks, monumental constructions that can be up to 300, 500 meters long, 100, 200 meters wide and the ditches of the geoglyphs can be up to 5 meters deep. And so far my colleague, Dr. Denise Schaan, who has been working on agristate, thinks that most of them – these are earlier stages. There are 450 geoglyphs and they just started. But she thinks that they are ceremonial centers, because so far no _____ refuse areas where people that live in a village dump all the trash has been discovered at the sites.

Graber:     What stage of the research is this project in, to kind of quantify the human influence and impact on the Amazon? When did it start and how is this project going?

Iriarte:      Well the project we are just announcing the project. At the moment the project just started is a project that is – it is going to take four years. And yeah, we really would like to quantify it, at least in certain regions of the Amazon that past human impact. How are we going to do that is we are going to dig the archaeological sites and also make vegetation inventories; see the vegetation that is growing in archaeological sites and outside of archaeological sites. The idea is that once we have the vegetation inventories of the forest that is growing, what archaeological sites, the idea is that through the particular composition of the forest and also through the particular topography of the canopy, the structure of the forest and the remote sensing, the spectral signature we are going to try to identify what is the signature of these forests that have been impacted by humans in the past.

Because the remote sensors that are mounted on the LiDAR are the same ones on the Landsat and Moree satellites that cover whole Amazonia our idea is to try to extrapolate the signature that we get from our _____ study, it's more plotted to entire regions in the Amazon.

Graber:     What impact could this have? Who is this important for? Who needs to understand this and what's the import for the future?

Iriarte:      I think it's important, so far I think in general terms we can say that the human impact on Amazonian forests have been in some way neglected from most conservation issues. It is very important to know – we don't know yet – I'm not going to say that all these forests have been completely transformed by humans, but it's important to know that the human footprints in the forest. Because it's very important for conservation issues. Maybe the better biodiversity that we want to preserve is not only the research of millions of years of evolution, something that my ecology colleagues have studied in detail, but also our impact the result of human manipulation on the environment.

And then, for example, when we create national parks we need to take into account what is the baseline that we want to get back. We want to get to a so-called pristine forest or do we want to get to pre-Columbian times. And this is something that we need to have a discussion about that, and that's why I'm collaborating with two major _____ institutions, that is the Brazilian National Institute of Amazonian Research and the Brazilian National Institute of Space Research, to discuss with my colleagues and convey our results to inform the conservation community.

Graber:     Could it also have an impact, when you were talking about conservation, on the idea of human use of the Amazon? Could it show that there can be sustainable human use and manipulation and kind of interaction with the Amazon and that the forest is actually quite resilient in that way?

Iriarte:      Yes. The one thing we don't want to do is obviously give a green flag to developers, saying, "Well, in the past the forest was manipulated and now we can do whatever we want with the Amazon because they have been manipulating it for 15,000 years." I think there is a huge difference in scale on pre-Columbian land use and more than industrial agriculture. And in addition I think that most of the people, when they think that people have been manipulating the Amazon in the past, think of big fires and think of deforestation. This is not necessarily the way that pre-Columbian have been managing the Amazonian forest. It may well be that they are enriching the forest and keeping the forest, not the forest in it.

Mirsky:      Cynthia Graber, speaking with the University of Exeter's José Iriarte. You can catch more of Cynthia on our 60 Second Science podcast, as well as on her podcast called GastroPod, which is all about the science and history of food, just go to Gastropod.com.

Some other items of interest, we recently ran an episode about a new TV series called Science Goes to the Movies. A new episode airs tonight on CUNY TV here in New York, but it will also be available worldwide at CUNY.TV. They're going to talk about The Imitation Game, you'd expect that movie about Alan Turing to be on a show about science and movies. But they're also going to discuss the Sondheim musical movie Into the Woods. The science there, according to the website, is the "way in which Sondheim's complex music works with natural pattern recognition and meaning making in the human brain, the neurology of rhymes, and the often musically-induced phenomenon of involuntary memory." So look for that episode of Science Goes to the Movies at CUNY.TV.

And a few nights ago I stumbled onto a documentary on a local PBS station titled Julia Robinson and Hilbert's Tenth Problem. It's about the life and work of mathematician Julia Robinson. She was a MacArthur fellow, the first woman elected to the mathematical section of the National Academy of Sciences, and the first woman president of the American Mathematical Society. In fact, when she was elected to the NAS, according to the documentary, she did not have a faculty position because of outdated nepotism rules at U.C. Berkeley, where her husband, Rafael Robinson, was a professor, and because of the way women in academia were often treated. But no surprise, the college scrambled like hell to get her a faculty position once she was about to enter the National Academy.

Anyway, it's a fascinating story, both about her and the math she did. It's not a PBS production, so it's not up on their Web site, but keep an eye out for it, as it's apparently shown on occasion on local PBS stations. And check out the Web site for the film, which includes a trailer and a way to order it. Just google "Julia Robinson and Hilbert's Tenth Problem."

And while you're perusing the Web get your science news at our Web site www.ScientificAmerican.com, where you can check out our section on citizen science; these are real scientific research efforts that need your help to gather or analyze data, sometimes even in a game format, so you can contribute and have fun at the same time. And follow us on Twitter where you'll get a tweet whenever a new item hits the Web site; our Twitter name is @sciam. For Scientific American Science Talk I'm Steve Mirsky. Thanks for clicking on us.