Late-Holocene gallery forest retrogression in the Venezuelan Guayana: New data and implications for the conservation of a cultural landscape

Abstract

Fire is considered a major threat to forest conservation in the Neotropics. Palaeoecological studies are critical for understanding the long-term interactions of climate, fire, and human activities in the savanna-forest dynamic. Here, new data from palynological analyses conducted in sedimentary records from the northern edge of the Amazon Basin, the Gran Sabana, southeast of Canaima National Park (CNP) are presented. Four radiocarbon ages from Quebrada Kowana (QK) and two for Ariwe Fernland (AF) records showed that both are late-Holocene age (with extrapolated basal ages of 3100 and 3400 cal. yr BP, respectively). Both showed the occurrence of gallery forest until 1800 (QK) and 1600 (AF) cal. yr BP, with forest taxa reaching 60% and 40% of the terrestrial pollen sum, respectively. The main forest taxa were Celastraceae, Moraceae/Urticaceae, Schefflera, Protium, and Mahurea (QK) and Dimorphandra, Protium, Schefflera, Tachigali, and Blepharandra (AF). Savanna herbs (mainly Poaceae) reached 40-50% (QK) and 60% (AF). The high abundance of savanna herbs together with the low occurrence of mature forest taxa, and high abundance of pioneer taxa, suggests that the former forests comprised very open and disturbed forest-belts, surrounded by savannas. Since 1800 (QK) and 1600 (AF) cal. yr BP, forest taxa dropped to 10% and 5%, respectively, suggesting the substitution of forests by herbaceous communities. The high abundance of charcoal recorded from the beginning of the records to about 1800-1600 cal. yr BP suggests that recurrent fires spreading from neighboring savannas were reaching the former forest, causing compositional changes and triggering forest reduction. Fires were very likely human-made, but highly controlled by climate. Hence, forest substitution happened when a combination of local fires and droughts was given in every record. Results agree with those from other localities in the CNP in confirming the occurrence of regional-scale gallery forest degradation during the late Holocene.

Rivers shape population genetic structure in Mauritia flexuosa (Arecaceae)

“…In the Gran Sabana of Venezuela and likely in the contiguous Roraima savannas of Brazil (e.g., BVI), the gallery forest was more dominant than the savannas 3,100-1,800 Cal yr BP (Leal et al, 2016). bility that it has adapted to re-colonizing habitats disrupted by fire.…”

From fire suppression to fire management: Advances and resistances to changes in fire policy in the savannas of Brazil and Venezuela

“…First, in ecological and paleoecological sciences, the idea that South American savannas resulted from the degradation of forests due to fire (Dezzeo et al., ; Rull et al, ), especially in the savannas of the Amazon basin, was used by fire‐fighting public bodies to maintain suppression policies. This was done without taking in consideration the value of traditional Indigenous knowledge as a sustainable tool for fire management and the complex interactions between fire and ecosystem dynamics (Bilbao et al., ; Leal et al, ). The idea of savannas as “degraded lands” promotes deforestation of these ancient ecosystems, and serves as a type of “green legitimisation” to expand soybean and more recently eucalyptus plantations across already threatened traditional territories and protected areas (Bond, ).…”

Linking well-being with cultural revitalization for greater cognitive justice in conservation: lessons from Venezuela in Canaima National Park

“…Since fire is considered to be one of the key risk factors in the Gran Sabana (Bilbao and Vessuri 2006), the project also initiated a paleoecological reconstruction of the landscape history (Leal 2010, Leal et al 2016, an analysis of changes in the vegetation cover and land uses, and a study of fire behavior and its impacts in the Gran Sabana (Bilbao et al 2009(Bilbao et al , 2010 [2] . Results of these studies were presented and discussed at various community assemblies that were part of the joint research activities, which prompted important discussions about the historical and social factors that have caused landscape change in the area.…”

“…Likewise, the paleoecological reconstruction of the history of the Gran Sabana landscape revealed that in contrast to what has been commonly assumed, fire has been a permanent component of the Gran Sabana landscape for the last 7000 years (Leal 2010, Leal at al. 2016, similar to what has been reported in the Cerrado savannas in Brazil (Mistry et al 2005).…”

“…This counter-narrative of fire has been steadily finding its way into public discourse, through (a) academic publications (Bilbao et al 2009, Leal 2010, Leal et al 2016, (b) the organization of symposia and plenary discussions in congresses (García and Bilbao 2007), (c) discussions in local, national, and international training courses, and (d) popular publications via the national media, the international press, and the internet (Romero 2010, Morillo 2011, Barras 2015.…”