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.
When I first heard about this class in Peru, I had no idea that I was going to experience so much in such a short period. Our goal was to visit two lakes in Peru and raise sediment cores for paleoecology. The first lake that we went to was Laguna Huayabamba, which sits at about 3250 m elevation in the La Libertad region of the Peruvian Andes.
However, getting to this lake was no easy task. Before the hike even started, we had to obtain the necessary permits and permission from the local people. After several days of visiting different town officials and waiting for approval, we could set out on our adventure.
Lahr, M.M. et al. (2016) Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya. Nature 529, 394-398. doi: 10.1038/nature16477
Rademaker, K., Hodgins, G., Moore, K., Zarrillo, S., Miller, C., Bromley, G.R.M., Leach, P., Reid, D.A., Yepez Alvarez, W. & Sandweiss, D.H. (2014) Paleoindian settlement of the high-altitude Peruvian Andes. Science 346, 466-469. doi: 10.1126/science.1258260
da Silva, S.G. & Tehrani, J.J. (2016) Comparative phylogenetic analyses uncover the ancient roots of Indo-European folktales. Royal Society Open Science 3. doi: 10.1098/rsos.150645
Veenendaal, E.M. et al. (2015) Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents – how different are co-occurring savanna and forest formations? Biogeosciences 12, 2927-2951. doi: 10.5194/bg-12-2927-2015
Patterson, R.T., Huckerby, G., Kelly, T.J., Swindles, G.T. & Nasser, N.A. (2015) Hydroecology of Amazonian lacustrine Arcellinida (testate amoebae): A case study from Lake Quistococha, Peru. European Journal of Protistology 51, 460-469. DOI: 10.1016/j.ejop.2015.06.009
Pitulko, V.V., Tikhonov, A.N., Pavlova, E.Y., Nikolskiy, P.A., Kuper, K.E. & Polozov, R.N. (2016) Early human presence in the Arctic: Evidence from 45,000-year-old mammoth remains. Science 351, 260-263. DOI: 10.1126/science.aad0554
Moseley, G.E., Edwards, R.L., Wendt, K.A., Cheng, H., Dublyansky, Y., Lu, Y., Boch, R. & Spotl, C. (2016) Reconciliation of the Devils Hole climate record with orbital forcing. Science 351, 165-168. DOI: 10.1126/science.aad4132
Open access online:
Matthews-Bird, F., Gosling, W.D., Coe, A.L., Bush, M., Mayle, F.E., Axford, Y. & Brooks, S.J. (2015) Environmental controls on the distribution and diversity of lentic Chironomidae (Insecta: Diptera) across an altitudinal gradient in tropical South America. Ecology and Evolution. DOI: 10.1002/ece3.1833
Open access online:
Flantua, S.G.A., Hooghiemstra, H., Grimm, E.C., Behling, H., Bush, M.B., González-Arango, C., Gosling, W.D., Ledru, M., Lozano-García, S., Maldonado, A., Prieto, A.R., Rull, V. & Van Boxel, J.H. Updated site compilation of the Latin American Pollen Database. Review of Palaeobotany and Palynology 223, 104-115. DOI: 10.1016/j.revpalbo.2015.09.008
Valencia Castillo, B.G. (2014) From glacial to modern conditions: Vegetation and climate change under human influence in the Central Andes. PhD Thesis, Department of Environment, Earth & Ecosystems, The Open University.
Conservation, restoration and management strategies are employed to maintain Earth’s biological diversity and physical environment to a near “natural” state. However, the concept of “natural” is generally inexact and may include degraded landscapes. In absence of long-term empirical data of natural baselines, impacted assemblages (human altered baselines) could be falsely assumed to be natural and set as conservation or restoration goals. Therefore, the identification of long-term ecological baselines becomes a pressing requirement especially in threatened biodiversity hotspots such as the tropical Andes that were under human pressure for several millennial.
This thesis aims to identify ecological baselines for tropical Andean ecosystems based on multi-proxy palaeoecological reconstructions from three Andean lakes. Trends of vegetation change are used to identify when landscapes became anthropogenic in the Andes. Because vegetation assemblages at c. 10 ka experienced negligible anthropogenic impacts and had modern-like climate condition, this time was considered the most recent period likely to provide insight into natural ecological baseline conditions.
Changes in vegetation assemblages were evaluated over time departing from 10 ka around Miski and Huamanmarca, two sites that remained virtually impervious to human impacts. Baselines in Miski and Huamanmarca drifted continuously over time and showed that baselines are dynamic entities. The vegetation assemblages derived from Miski and Huamanmarca suggest that that human impact was not homogeneous throughout the Andean landscape.
Once baselines were defined it was possible to evaluate if the spatial distribution of Andean woodlands represented by Polylepis was a product of human impacts. A MaxEnt model generated based on 22 modern environmental variables and 13 palaeoecological vegetation reconstructions showed that Polylepis woodlands were naturally fragmented before humans arrived in South America (14 ka). However, the influence of humans during the mid and late Holocene enhanced the patchiness of the forest generating a hyper-fragmented landscape.