Title: Environmental change in the Yaque river area, northwestern Dominican Republic: Human impact before and after Columbus’ arrival in the New World
Date: Wednesday 26 October, 11:00-12:00
Location: Science Park 904 (please contact Henry Hooghiemstra for details if you want to attend)
Abstract: Multiproxy analysis of the 225-cm long sediment core Los Indios from the Yaque river valley in northwestern Dominican Republic (Hispaniola) shows environmental changes during the last 1150 cal yr BP. The observed changes show a period of little human distubance, followed by increasing human activity and a rapid intensification of these changes after Columbus’ arrival in AD 1492. The fastest changes on the landscape can be observed at 307 cal yr BP, when agricultural development in the Dominican Republic intensified.
Zoe and William just after the graduation ceremony (UvA)
Two students (Zoe van Kemenade and Tessa Driessen) have recently completed projects looking at past environmental change on Samoa working in the Research Group of Palaeoecology & Landscape Ecology at the University of Amsterdam (UvA). Zoe’s project, part of her BSc Future Planet Studies (major Earth Sciences) at UvA, was entitled “A multi‐proxy analysis on the effect of climate and human activity on the environment of Samoa during the Holocene” and investigated charcoal, macro-fossils, and algae. Tessa’s project, “Biodiversity, fire and human dynamics on Samoa over the last 9200 years”, was completed as an internship during her MSc in Environmental Biology at Utrecht University (UU) that was co-supervised by Rike Wagner-Cremer. Tessa focused on the fossil pollen record to reconstruct past vegetation change. Both projects were conducted in cooperation with Jon Hassel and David Sear (both University of Southampton) who provided access to the Samoan sediments; for more on the Southampton Pacific Islands projects check out their blog Palaeoenvironmental Laboratory at the University of Southampton.
The results from both projects, and work by the University of Southampton team, will be presented at this years GTO conference (European conference of tropical ecology) in Gottingen next week.
William giving his personal view on the work of Tessa at her gradation ceremony (UU)
Hayley Keen getting excited about sediments during fieldwork in Ecuador (2012). Photo: J. Malley
Keen, H.F. (2015) Past environmental change on the eastern Andean flank, Ecuador. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.
Abstract The eastern Andean flank of Ecuador (EAF) contains some of the world’s most biodiverse ecosystems. Andean montane forests are threatened due to anthropogenic pressures and both current and projected climate change. This thesis examines the palaeoecological history of two stratigraphic sequences (Mera Tigre West [MTW] and Mera Tigre East [MTE]) obtained from the Ecuadorian modern lower montane forest. The sediments preserved were analysed using eight analytical techniques, allowing an insight into the ecosystem’s potential response to projected changes derived from their past responses. Palaeoecological studies on the EAF are rare, and those that do exist are debated relating to: i) the inference of robust ecological data from pollen records in floristically diverse locations, and ii) the past source area of sediments preserved in fluvially exposed sequences, potentially leading to contamination with older material.
A statistical sub-sampling tool was developed (debate i), capable of producing statistically robust count sizes for each pollen sample; MTW and MTE count sizes ranged from 196-982 showing the diversity within sequences. The depositional environment of MTE was analysed, investigating sediment provenance throughout (debate ii). Results found that large scale volcanic events were critical in the preservation of the sediments, whereas fluvial influence caused a regional sediment source area in the upper stratigraphy, impacting on the palynological interpretation of MTE. Pollen records demonstrated the presence of a diverse vegetation community with no modern analogue at MTE (abundant taxa (>15 %): Hedyosmum, Wettinia, Ilex) and upper montane forest at MTW (Alnus, Hedyosmum, Podocarpus). Fire was not the main driver for the vegetation reassortment at either site (MTW correlation coefficient: -0.37, MTE: 0.16). The two sites have demonstrated the EAF plays host to floristically dynamic ecosystems, susceptible to drivers of change (fire and landscape) and should be considered when predicting the montane forests’ future response to environmental change.
Last week we changed our regular lab meeting, when we all normally discuss a particular paper, to each presenting a general view on the articles published in the first issue of the new journal The Anthopocene Review (SAGE publication). In this lab meeting each member presented and lead discussion of issues within a different paper.
In my case, I had a very interesting paper by Anthony J McMichael about changes in life expectancy (Human population health) related to the human impact caused at global scale during the Anthropocene (defined in the paper as the last 200 yr). Here is a brief summary of the main topics discussed in the paper:
The paper deals with life expectancy trends during the human history on Earth, understood not as the individual health care but as a population or community collective (the “herd” effect), being this two independent topics.
The first section is a nice trip for human evolution and its relationship with the environment, distinguishing three different phases of environment-climate-human relationship:
The Pleistocene (c. 2.6 million – 11,000 years ago): characterised by environment-driven changes;
The Holocene (c. 11,000 – 200 years ago): with cultural-driven changes promoted by the potential of farming. Survival, although relying in culture changes, was still dependent on climatic stability (survival changes caused or amplified by adverse conditions); and
The Anthropocene (last 200 year, as defined in this paper): when humans have become a dominant force on the world stage, being nowadays the major contributor to climatic change.
Finally, the author shows several direct and indirect pathways by which changes in climatic conditions will affect the human health, encouraging the urgent need of an environmentally sustainable way of living.
If you are interested to find out what your ecological footprint might be try these online tests:
Miller, C.S. (2014) 520,000 years of environmental change in West Africa. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.
Global temperatures are predicted to rise by 2–2.5°C by 2065, profoundly affecting the Earth’s environment. The response of ecosystems to past climate fluctuations can inform on how systems will respond in the future. This thesis focuses on Quaternary environmental changes in West Africa, a region important because of its high ecological value and role in the global carbon cycle.
In 2004, the International Continental Drilling Program recovered c. 291m of sediments spanning the last c. 1 Myr from Lake Bosumtwi (Ghana). Pollen, charcoal and nitrogen isotopes (d15N) were analysed from the most recent c. 150m (c. 520 kyr). The latitudinal position and long duration of this core makes it unique for understanding West African monsoon dynamics and vegetation change.
To aid characterisation of the Bosumtwi pollen succession, an atlas of present-day pollen was constructed for 364 pollen and spore taxa.
The pollen record from Bosumtwi reveals dynamic vegetation change over the last c. 520 kyr, characterized by eleven biome shifts between savannah and forest. Savannah vegetation is dominated by Poaceae (>55%) associated with Cyperaceae, Chenopodiaceae-Amaranthaceae and Caryophyllaceae. Forest vegetation is palynologically diverse, but broadly characterised by Moraceae, Celtis, Uapaca, Macaranga and Trema. Low d15N values correspond to forest expansion and these are driven by high lake levels. The timescale indicates that the six periods of forest expansion correspond to global interglacial periods. The record indicates that the wettest climate occurred during the Holocene, and the driest during Marine Isotope Stage 7.
The vegetation and d15N records show a strong response to glacial-interglacial variability between c. 520–320 kyr and 130–0 kyr. Between c. 320–130 kyr there is a weaker response to glacial-interglacial cycles probably related to high eccentricity during the peak of the 400-kyr component of eccentricity, with high eccentricity resulting in greater seasonality and ultimately drier conditions.