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.

Palaeo-science in the Pyrenees at PAGES YSM 2017

Morillo de Tou – the beautiful location of the YSM

I recently attend the PAGES (Past Global Changes) YSM (Young Scientists Meeting) as well as the OSM (Open Science Meeting) 2017 in sunny Spain. The YSM was particularly exciting – a group of 80 early career researchers met in the Pyrenees, at the restored village of Morillo de Tou.

Morillo de Tou

Morillo de Tou

 

The spectacular surroundings were matched by spectacular science, with a combination of great talks and posters as well as breakout group discussions and workshops. The schedule was pretty packed, but we made time for some star gazing with local astronomers and a night of traditional Aragon music and “dancing” in the moonlight. Overall, I thought the YSM was an excellent opportunity to meet other young scientists, and discuss issues of particular import to our community.

A highlight for me was the breakout discussion on communication with the public and communicating the relevance of palaeo-science to funders and policy makers. We had some great discussions in our group, centering on the need to engage children in science from a young age. We also talked about the importance of telling a story when you present your work, and how talking to politicians and journalists in a positive, optimistic way can enhance engagement.

We also discussed the idea of setting up a PAGES working group for young scientists, with regular meetings to discuss funding, careers and to network. Watch this space!

 

The conference venue at Morillo de Tou

 

I enjoyed presenting my PhD work in the Monday morning session, and received some helpful feedback from fellow YSM participants through a peer review scheme. I think the scheme was a great way to encourage everyone to consider their own presentation style, by reviewing their peers’.

A further benefit of attending the YSM was that we already knew 80 people attending the OSM in Zaragoza, so there were plenty of friendly faces amid the ~900 OSM participants. This made the OSM much less intimidating and more enjoyable. Overall, the organisation of the YSM was incredible and I would certainly encourage early careers researchers to attend the next one in 2021. The only complaint was the cold coffee at breakfast – conference mornings without coffee are a tough sell for sleepy PhD students… but the beautiful Spanish sunshine more than made up for it.

Morning views across the lake at Morillo de Tou

 

If you’re interested in what went on at PAGES 17 (YSM and OSM) check out the #PAGES17 on twitter for some great insights.

By Heather Plumpton 

@heatherplumpton

 

 

 

PhD opportunity with us

 

NERC ‘Scenario’ DTP PhD project at University of Reading:

 Assessing the resilience of Brazil’s iconic Araucaria forest

to past and future climate change

 

Araucaria

 

Lead Supervisor: Francis E. Mayle, Dept. Geography & Environ. Science, Univ. Reading.

Email: f.mayle@reading.ac.uk

Staff profile 

Broader context of the project 

Co-supervisors: Richard Walters, School of Biological Sciences, Univ. Reading; Joy Singarayer, Dept. Meteorology, Univ. Reading; Macarena Cárdenas, Dept. Geography & Environ. Science, Univ. Reading.

Collaborator: Jose Iriarte, Dept. Archaeology, Univ. Exeter.

 

Background:

The Parana pine (Araucaria angustifolia) of southern Brazil is an iconic ‘living fossil’, dating back to the Mesozoic, when it was likely grazed upon by Sauropod dinosaurs.  This evergreen conifer once dominated highland areas of Brazil’s southern Atlantic Forest (a global biodiversity hotspot) until the colonial period, but is now critically endangered and is a key conservation priority.  To gain a robust understanding of the likely response of Parana pine to future climate change, a better understanding of the underlying reasons for its current biogeographic distribution is first needed, which can only be gained via knowledge of the long-term dynamics of this species over the past several millennia, in relation to both past climate change and pre-Columbian (pre-1492) human land use.  The overall aim is to determine the relationship between Araucaria forest, climate change, and human land use over the past ~ 6,000 years in southern Brazil, and thereby improve understanding of the likely response of this species to future climate change and the implications for conservation policy.  This PhD project complements an ongoing AHRC(UK)-FAPESP(Brazil)-funded project which provides the archaeological context.

 

Approach and Methods:

The student will use a novel, multi-disciplinary approach, which combines palaeoecological and archaeological data with ecological and climate models.  Fossil pollen will be analysed from bog sediments and fed into land-cover models (REVEALS, LOVE) to reconstruct the history of Araucaria forest over the last ~ 6,000 years.  These data will be integrated with ongoing archaeological studies and previously published palaeoclimate records to determine the respective roles of people versus climate change in driving late Holocene Araucaria expansion.  Climate models and ecological niche models (e.g. MAXENT) will be tested against these palaeo data and used to map the environmental niche of Araucaria through time, in response to past and future climate change.

Training opportunities:

Training will be given in field- (bog coring) and laboratory-based (pollen microscopy) palaeoecological skills (Mayle & Cárdenas), climate (Singarayer) and ecological (Walters) modelling, and integration with archaeological data (Iriarte).  Sediment cores have already been collected, but there will be scope to visit the field area and collect further material if necessary and any relevant ecological data.

Student profile:

Applicants should hold a minimum of a UK honours degree at 2.1 level, or equivalent, in a relevant subject such as biology, geography or environmental science.  A strong background in numerical/statistical techniques is essential and knowledge of ecology, microscopy and coding/modelling would be advantageous.

 

How to apply:

Full details of how to apply, as well as a podcast of this advert, can be found at:

http://www.met.reading.ac.uk/nercdtp/home/available/

The deadline for applications is 25th January 2016, although later applications may be considered.  For further details about the project, please contact the lead supervisor, Francis Mayle.