Vegetation responses to late Holocene climate changes in an Andean forest By Klaas Land (currently studying MSc Biological Sciences (Ecology & Evolution) at the University of Amsterdam.
The discussion during the APC meeting on the 19th of March was on the paper by Schiferl et al. (2018), a very recent study on the climatic shifts in the late Holocene and their effects on the South American tropics. The study had analysed a core going back about 3800 years from Lake Palotoa, which was in the Andean foothills (1370m elevation). They found that subtle changes to the fossil pollen record could be identified around the estimated periods for the Little Ice Age (LIA) and Medieval Climate Anomaly (MCA). The focus in the paper Continue Reading
In the 4th edition of our “Amsterdam Paleoecology Club”(APC), we discussed ‘A 6900-year history of landscape modification by humans in lowland Amazonia’ by Bush et al. (2006)1. The high-resolution record presented in this paper shows impressively that what we might perceive as native rainforest today could rather be a since a long time actively modified landscape.
The chronology from Lake Sauce (Peruvian Andes) suggests a continuously forested landscape under significant anthropogenic impact over the last 6900 years. Indicators of human activity are taken to be the varying presence of crop pollen (Zea mays) throughout the record, combined with the continuous occurrence of charcoal. Two extra-large fire events are dated at c. 6700 and between 4500-4230 cal BP, probably enhanced by the relatively drier climate of the mid-Holocene. However, it is not clear yet if human actions formed a response to climate change or were part of social and cultural changes.
For this “Amsterdam Palaeoecology Club” (APC) meeting we did not discuss a paper, instead I presented my progress on my second research internship of my master’s on the geolocation of pollen samples under the supervision of dr. C. N. H. McMichael. The other students were asked to read the paper ‘Forensic palynology: Why do it and how it works’ by Mildenhall et al. (2006). This paper gives a review of the use of palynological analysis for criminal investigation, which ties in with my research.
The paper we discussed was “Columbus’ footprint in Hispaniola: A paleoenvironmental record of indigenous and colonial impacts on the landscape of the central Cibao Valley, northern Dominican Republic” by Castilla-Beltrán et al (2018). The paper provides a multi-proxy paleoecological reconstruction of the Caribbean island nation of the Dominican Republic, spanning the last 1100 years. Personally I found this to be a very interesting paper, packed with information and interpretations on the impact of anthropogenic factors on past Caribbean environments. What this paper nicely demonstrates is the difference in impact between pre-colonial and post-colonial societies on the vegetation of the Dominican republic. Pre-colonial Hispaniola was inhabited by indigenous societies, the Taíno people, and while this paper clearly shows them having had an environmental impact in the form of fire management (e.g. for slash and burn agriculture), small scale deforestation and the introduction of cultivars such as maize and squash, their environmental impact remains modest compared to post-colonial disturbances. Columbus arriving in AD 1492 signified a moment of change in the landscape. The paleorecord suggests that, after an initial collapse of the Taíno population, the colonization of the Dominican Republic by the Spanish brought with it deforestation, crop monoculture and the introduction of European livestock, all of which still characterizes the landscape to this day.
The discussion mainly focused on the chronology used. One of the radiocarbon samples was excluded from the age-depth model for no apparent reason, which led us to discuss the importance of critically evaluating your calibrated radiocarbon dates and which ones to incorporate in your age-depth model. The age-depth model currently used implied a shift in pollen composition c. 30 years before the arrival of the Spanish. We were unsure how to interpret these findings because you would expect the shift to happen afterwards, so my initial thought was that it had to be a fault in the chronology. This chronology however does imply a large charcoal peak followed by a rapid decline that coincides precisely with the arrival of the Spanish, and it turned out that this was the reason the authors settled on this chronology.
Even though this paper by Castilla-Beltrán et al. didn’t spark any heated discussions, its incorporation of ecology, botany, history, archeology and geology still showcases the interdisciplinary nature of paleoecology, something I very much enjoy about this field of research.
This is the first is a series of blog posts based on papers discussed at our “Amsterdam Palaeoecology Club” meetings. The APC meetings are organized to promote palaeoecological discussion and to help the scientific development of our MSc and BSc research students. At each meeting we discuss a paper and the progress of individual projects. Short summaries of the papers and discussions are then made by the student introducing the paper. First up is MSc researcher Rianne van Duinen with her thoughts on Kaplan et al. (2016).
Rianne on field work in Twente during the 2017 edition of the BSc Palaeoecology course at University of Amsterdam
We discussed the paper “Large scale anthropogenic reduction of forest cover in Last Glacial Maximum Europe“ by Kaplan et al. (2016) which was found by the group to be super interesting and it incited a lot of discussion. The paper was mostly concerned with the anthropogenic influences and past vegetation of Europe. The main conclusion was that humans had a very big impact on forests during the last glacial period through the use of fire. The authors suggest that human actions are the explaining factor for the low amount of forests cover suggested by pollen records during the last glacial maximum (c. 21,000 years ago). The suggestion from Kaplan et al. that human modification of forest cover through fire during the glacial links with a recent study from Sevink et al. (2018) that suggests, based on pollen and charcoal data from the Netherlands, that human use of fire altered forest cover into the Holocene. In our discussion it was also noted that animals (mega-herbivores) were not really taken into account or discussed, even though animals probably had a big impact on the vegetation (e.g. see Bakker et al., 2016). Furthermore, another discussion point was the charcoal records that were used in the Kaplan et al. study, more specifically the number of cores. Kaplan et al. only used three cores to map out the effect of charcoal. It would be interesting to see what happens when more data from more cores is used. The Global Charcoal Database has a lot of data on European cores (c. 38% of the cores are from Europe) so there is a lot of potential for this. All in all, the article by Kaplan et al. raised a lot of questions and opened up a nice discussion.
Since being appointed as an Associate Editor of Vegetation History & Archaeobotany last year I have the pleasure of working on a number of exciting and interesting manuscripts from the tropics. I am particularly delighted that the first of these (Astudillo, 2018) has now been published. I particularly liked this manuscript because of: (i) the close relationship that was shown between the historical and fossil records, and (ii) the clear signal shown from working on a island system. This linkage is something I have been thinking about in my own research on Mauritius recently (Gosling et al., 2017) and is, I believe, particularly valuable to do because it demonstrates the validity of techniques to track human activity when applied in contexts without historical documentation. The impact of people on the Galapagos is shown by Astudillo (2018) from investigation of multiple proxies (charcoal, phytoliths and macrofossils) to build up a comprehensive picture of human impacts on one of the most famous places for biodiversity on Earth. Hopefully this study is just the start of investigations into past human impacts on the Galapagos islands, and I hope that you enjoy reading the manuscript!