Holocene Paleoecology in the Neotropical Savannas of Northern South America (Llanos of the Orinoquia Ecoregion, Colombia and Venezuela): What Do We Know and on What Should We Focus in the Future?

Daniela Piraquive-Bermúdez,Hermann Behling

doi:10.3389/fevo.2022.824873

Abstract

We provide an overview of the Holocene paleoecology of the Llanos ecoregion. A region that captured the attention of researchers for more than 200 years, as it exhibits a high heterogeneity in landscapes and vegetation, where savanna and forest mosaics exist. Located in an area influenced by the seasonal migration of the Intertropical Convergence Zone (ITCZ), it provides a unique area for understanding long-term dynamics of climate, vegetation and human history. Twelve locations have been paleoecologically studied, showing general vegetation and climate changes trends since the Last Glacial Maximum (LGM). During LGM savanna herbs were dominant, indicating dry climatic conditions. The transition of the Holocene was characterized by a slight increase in forest taxa, suggesting a transition to a wetter climate. Between ∼10,000 and 7,000 cal yr BP, grasslands were abundant, and few forest taxa, including Mauritia were also common but rare, pointing to a warm and humid climate. After ∼7,000 cal yr BP, the gallery forest started to expand, suggesting a change to a wetter climate. Mauritia palms increased markedly after 4,000–3,000 cal yr BP, possibly driven by higher mean annual precipitation and/or longer wet season. The start of human occupation remains unclear, but it has been linked to the time of expansion of Mauritia, a period in which fires, possibly of anthropogenic origin, were more frequent. To understand patterns of change in these ecosystems, it is necessary to improve the chronological control of the sediments in future studies and increase the resolution and proxies used to reconstruct their history.

Highlights

The Llanos Orientales in Colombia and the Orinoco Llanos in Venezuela, known as the Llanos of the Orinoquia ecoregion, represent the second-largest Neotropical savanna ecosystem covering more than 500,000 km2 with an extension of about 1,200 km
The savanna starts at the foothills of the Colombian Oriental Andes extends along the Orinoco River to the swampy forest and Holocene Paleoecology in the Neotropical Savannas wetlands of eastern Venezuela, almost to its delta (Berrio et al, 2002)
In 1799 Alexander von Humboldt and Aimé Bonpland started their expedition along the Orinoco River in Venezuela; they described and collected valuable information about the savannas and the gallery forest, its composition, ecology, and the seasonal contrast in the Venezuelan Llanos (Wulf, 2015)

Summary

INTRODUCTION

The Llanos Orientales in Colombia and the Orinoco Llanos in Venezuela, known as the Llanos of the Orinoquia ecoregion, represent the second-largest Neotropical savanna ecosystem covering more than 500,000 km with an extension of about 1,200 km. Two well-defined landscapes exist the high llanos (locally known as llanos arriba), reaching 300 m asl, and the low llanos (llanos abajo) (Gassón, 2002), while the natural vegetation can be summarized in four types: forest, dry savannas, wet savannas, and swamps (Figure 1; Etter, 1998; Rangel-Ch, 2019) These ecosystems harbor a high ecological diversity and provide different services for the local fauna and human populations. Since the 1980s, the establishment of large-scale intensive agriculture (palm oil—Elaeis guineensis and rice) and increased human population have modified the natural savannas and forest of the Llanos Orientales Other activities such as cattle expansion, road infrastructure, petroleum activities, mining and illicit crops have contributed to land degradation and turned it into one of the most threatened ecosystems in Colombia (Romero-Ruiz et al, 2012).

A BRIEF HISTORICAL VIEW

How climate change influenced the dynamics of vegetation and fire?

Findings

How will these ecosystems change under future climatic scenarios?