Ancient human impacts in Amazonia – the debate continues…

How well can you ever really know 5.5 million km2 of hyperdiverse forest? The Amazon region, and this question, are at the heart of several ongoing debates in the natural sciences – why are there so many species? how much carbon can the forest store? how much did ancient humans impact the forests, and can we still see their effects today?

How fully can you really know a forest as huge and diverse as the Amazon?

This last question was the subject of a paper by Caroline Levis and colleagues published in the prestigious journal Science in March this year, which caused significant ripples within and outside the scientific community. In a nutshell, the article found that tree species humans have cared for are five times more likely to be forest ‘hyperdominants’ than you’d expect. Past human impacts also help explain where these species are found now, accounting for up to 20% of the variation in their distribution (for comparison, environmental factors explained up to 30%). The paper’s conclusion, as picked up by the media, is that “modern tree communities in Amazonia are structured to an important extent by a long history of domestication by Amazonian peoples.”

Theobroma cacao – the tree cocoa beans come from – was one human-influenced species in the Levis et al study

So, debate settled? Not quite. Responding to the paper some critics pointed out that the potential influence of soil nutrients hadn’t been adequately considered; others suggested the data showed that human effects were only significant within 20km of archaeological sites; and yet another argued that most of the human-influenced trees are so short-lived that pre-colonial individuals would be dead by now. Furthermore, another study published around the same time showed these Amazon forest plots are disproportionately close to places highly affected by ancient humans, so maybe it was inevitable that the sampled areas would still be showing their influence.

This, perhaps, goes to the heart of the problem with trying to uncover the human history of all Amazonia: there isn’t much detailed region-wide environmental data, the non-random tree plots cover a vanishingly small fraction of the forest, and there are many archaeological sites we may never find. Reflecting on the paper and its findings at a recent TPRG meeting, it was sobering to consider how this can limit the conclusions of wide-ranging studies like this.

It was also striking how, when it comes to ancient human impacts on forests, people can draw very different conclusions from the same data. As I embark on my research into the effects of past humans and climate change on southern Brazil’s Araucaria forests, these will certainly be important things to bear in mind!

Oli

@olijwilson

The original paper by Caroline Levis and colleagues can be found here: http://science.sciencemag.org/content/355/6328/925. Some scientists have responded to the paper in its eLetters section (http://science.sciencemag.org/content/355/6328/925/tab-e-letters), and Christopher Dick posted his thoughts on his research group website (http://sites.lsa.umich.edu/cwdick-lab/2017/03/18/a-critical-take-on-persistent-effects-of-pre-columbian-plant-domestication-on-amazonian-forest-composition). The paper on the link between forest plots and areas of ancient human impact was published by Crystal McMichael et al., and can be found here: http://www.pnas.org/lookup/doi/10.1073/pnas.1614577114.

Anthropology, Weather & Climate Change Conference

THE ROYAL ANTHROPOLOGICAL INSTITUTE AND THE DEPARTMENT OF AFRICA,

OCEANIA AND THE AMERICAS OF THE BRITISH MUSEUM

RAI

27-29 May 2016

 

Aimed to understand past vegetation and its interaction with human, our group was moved to propose a panel in this conference where multiple disciplines of research as well as the private sector could come together to discuss about the environment-human relationship.

 

About the panel:

 

 Indigenous populations-vegetation-climate relationship in the past: what can this teach us about sustainable vegetation use in the present? (P31)

 

 

This panel invites multiple research disciplines and concerned private and public sectors to share evidence and discuss how knowledge of past climate change and past land use by indigenous cultures help us to understand what affects the vegetation and how this information can be used to protect it.

To know more about the conference, click here

Or contact us for more information about this panel

 

 

Panel abstract:

Threats of climate change and expanding human urbanisation makes the future of worldwide vegetation uncertain. Increasing demands of land for the growing global human population adds pressure to people and governments to protect the remaining native vegetation. Nevertheless, are the large efforts of protecting what seems to be the last places of “pristine” vegetation adequate or enough?

 

Understanding the impact of different factors in changing the vegetation is crucial for their protection. Although modelling is becoming a valid methodology to determine the main factors involved in vegetational change, it is still not specific enough to account for individual communities. Specific information of how the vegetation responds to climate change and human impact can be found in palaeoecological, palaeoclimatic and archaeological studies; these studies give us clues to how the vegetation responds to main factors from millennial to centennial time scales. Combining these disciplines we can also help us to understand the role that past human populations had within a specific landscape allow us to evaluate the role that past humans played in shaping the vegetation we see today.

 

Here we propose a discussion amongst archaeologists, palaeoecologists, palaeoeclimatologists, human geographers, anthropologists, policy makers and NGOs to share both evidence and techniques as well to discuss to what extent past cultures and climate modulated the vegetation we see today in areas considered pristine or well preserved. Special emphasis is to evaluate what can be learned about past cultures and their vegetation/landscape use to help land management and conservation today. We expect this discussion to help integrate valuable knowledge and facilitate decision making today in creating, protecting and improving endangered vegetation communities.

 

 

 

 

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