Chapter 2

Abstract

We provide an overview of environmental and climatic change in Colombia during the Quaternary, the last ca. 2.58 million years (Ma) before present. This period is characterised by a suite of glacial-interglacial cycles which are remarkably well documented in Colombian sediments. The distribution of Colombia's main ecosystems has changed repeatedly driven by orbital forcing at 21, 41, and 100 ky frequencies which were superimposed by millennial-scale (ca. 2.5 ky) climate oscillations. Fossil pollen records have detected biome dynamics through time but records vary in length: the shortest comes from the Chocó rainforest (extending back to ca. 7 thousand years before present, ka) and dry inter-Andean forest (ca. 12 ka), followed by the savannas of the Llanos Orientales (ca. 20 ka), the Amazonian rainforests (ca. 40 ka), and lower montane forest (ca. 40 ka). The longest records are from the deep sedimentary basins Bogotá (Funza09, last 2.25 Ma) and Fúquene (last 284 ka), alternatingly located in the upper montane forest and páramo during interglacial and glacial conditions, respectively. Climate change caused shifting biome distributions: mainly latitudinally in the lowlands and elevationally in the mountains. Extrinsic drivers (e.g., mean annual precipitation, length of dry season, atmospheric pCO 2 , mean annual temperature, freezing days) of migration and changes in vegetation composition and intrinsic drivers (such as interspecies competition and legacy effects) are still insufficiently understood, and thus hamper meaningful projections of the effect of future environmental change on biomes. Multi-site Pleistocene and Holocene information has been spatially synthesised by developing the Latin American Pollen Database. Multi-site information has been analysed by the biomisation method to serve palaeodata-model comparisons and projections about the future of biomes in Colombia. A new method in which pollen-based palaeo-reconstructions are spatially analysed with digital elevation models improved our understanding of spatial and elevational shifts of ecotones, for example the upper forest line, in the northern Andes. In the Supplementary Information we highlight the strengths and weaknesses in current Quaternary palaeoecological research and provide suggestions for future research.

Constraints on the paleoelevation history of the Eastern Cordillera of Colombia from its palynological record

“…4A and 5A). Both of these taxa immigrated from North America to the Eastern Cordillera in Pleistocene time, and hence both are absent in Pliocene and Miocene pollen assemblages (Felde et al, 2016;Hooghiemstra and Flantua, 2019;Hooghiemstra and Ran, 1994;Hooghiemstra and Van der Hammen, 2004;Hooghiemstra et al, 2006;Torres et al, 2013;Van der Hammen, 1974). Moreover, because they competed with and to some extent replaced other taxa that had thrived in the same environments for millions of years (e.g., Hooghiemstra and Van der Hammen, 2004;Torres et al, 2013), a test in which the dominant taxa are immigrants and not representative of past assemblages is less than ideal.…”

“…With many decades of study, Dutch and Colombian botanists have made the Eastern Cordillera of the Colombian Andes (Fig. 1) a test area for characterizing how tropical plants live and evolve along elevation gradients in the tropics (e.g., Hooghiemstra and Flantua, 2019). A by-product of this work has been steadily evolving images of how the Eastern Cordillera itself has risen to its present-day height in late Cenozoic time.…”

The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes

“…Recently, Hooghiemstra and Flantua (2019) reviewed the studies of northern Andean fossil pollen records for the upper and the lower montane forests (UMF and LMF, respectively), which are the biomes where Q. humboldtii is distributed (Hooghiemstra, 2006;Rangel-Ch & Avella, 2011). They describe that during the last glacial maximum (21 ka BP to ~14 ka BP), a period characterized as extremely cold and dry (van der Hammen, 1974), the upper forest limit reached an elevation of ~2,000 m (van der Hammen & Cleef, 1986), and the UMF was displaced to a lower elevation and compressed by ~400 m compared to today's altitudinal range (Figure 1a,b).…”

Presentation

“…In chapter 2, Hooghiemstra & Flantua (2019) summarize sixty years of palynological research in the Colombian territory. The authors present an overview of Quaternary history through the identification of environmental and climate changes characterized by a set of glacial-interglacial cycles very well-documented in the Quaternary sedimentary record of Colombia.…”