Holocene Fires and Ecological Novelty in the High Colombian Cordillera Oriental

Abstract

Rapid climate changes and the increasing presence of humans define the Holocene Epoch (11.6 calibrated kiloyears before present – hereafter kyr BP), when biological systems have faced the most recent and abrupt environmental changes. Understanding how biodiversity responds to extrinsic factors requires determining the effects of varying climatic conditions, changes in disturbance regimes, and increasing anthropogenic impacts. Despite being one center for biodiversity, the potential synergies of long-term anthropogenic and climate changes in shaping areas of high Andean biodiversity have yet to be explored fully. Here we present new pollen and charcoal records from the Pantano de Monquentiva (hereafter Monquentiva) on the highlands of the eastern flank of the Colombian Cordillera Oriental (CCO) to document relationships between climate, vegetation, and fire through the Holocene. We found compositional transitions at 8.7, 6.1, and 4.1 kyr BP at Monquentiva resulting from the interaction of climate, fire, and human occupation. Reduced moisture and temperature caused a compositional shift in Páramo vegetation from ca. 8.7 kyr BP. Fire activity was recorded throughout the Holocene and increased slightly during the Mid-Holocene when regional and local fire decoupling suggested human activities as the source of ignition. Mid-Holocene fires had a large effect on the vegetation composition at Monquentiva which recorded a rapid shift at ca. 6.8 kyr BP. Fire activity increased sharply from 4.1 kyr BP, promoting the reorganization of plant communities at 3.8 kyr BP. This shift in fire activity was likely related to more severe ENSO events and subsequently intensified by human activities after 3.8 kyr BP. Although high climatic sensitivity explains most Holocene vegetation changes in the eastern flank of the CCO, our study highlights the relevance of fire activity, uneven distribution of climatic variables, and human intervention to the composition of the vegetation we see today.

The timing and ecological consequences of Pleistocene megafaunal decline in the eastern Andes of Colombia

“…During the late Holocene, fire activity escalated at Monquentiva (Espinoza et al, 2022) (Supplementary Figure 3, Fig. 6).…”

“…6). High charcoal concentrations likely reflected increased fires linked to agriculture (Gómez et al, 2007) and other anthropogenic activities (Espinoza et al, 2022). Thus, the escalated fire record during Late Holocene megafaunal presence is likely to have been induced by human activities and facilitated by climate, which coupled to override the suppressive effect of megafauna on the vegetation.…”

“…Small streams on the eastern side of the mountain range contribute to the site's hydrology, which feeds into the Orinoco River basin (Avella-M et al, 2014). During pre-Hispanic times, Monquentiva was prone to flooding and may have contained a water body (Avella-M et al, 2014; Espinoza et al, 2022). The contemporary peat bog underwent transformations through the establishment of colonial drainage systems for livestock (Gomez and Rubio, 2003; Avella-M et al, 2014).…”

“…The contemporary peat bog underwent transformations through the establishment of colonial drainage systems for livestock (Gomez and Rubio, 2003; Avella-M et al, 2014). The shape and position of Monquentiva are controlled by the Río Blanco-Machetá Anticline fold and Machetá fault (Kammer et al, 2020; Espinoza et al, 2022) built upon sedimentary Cretaceous rocks (Kammer et al, 2020).

Figure 1.Location of the study site.

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“…The climate, geographical location, and topography of Monquentiva favour a mosaic of vegetation and concentration of biodiversity along a narrow altitudinal gradient in which the High Andean Forest, Subpáramo, and Páramo are the most abundant vegetation types (Avella-M et al, 2014; Espinoza et al, 2022). High Andean forest is the most represented vegetation surrounding Monquentiva today (76%), where Weinmannia and Clusia dominate (Avella-M et al, 2014).…”