The Paleoanthropocene of the Yucatán Peninsula: palynological evidence of environmental change

Boletín de la Sociedad Geológica Mexicana / 2018 / 49 Gerald A. Islebe Nuria Torrescano-Valle Alejandro A. Aragón-Moreno Alejandro A. Vela-Peláez Mirna Valdez-Hernández El Colegio de la Frontera Sur, Herbario, Departamento Conservación de la Biodiversidad, Avenida Centenario km 5.5, Apartado Postal 424, CP 77014, Chetumal, Quintana Roo, México. ABSTRACT RESUMEN Human activities have changed and shaped landscape conditions of the Yucatán Peninsula for more than 4000 years. Several paleoecological studies showed the oldest pollen record of corn-based agriculture is from northern Belize, with an estimated age of 3300 BC. Several other studies report maize between 1500 and 3000 BC from northern Guatemala and the Mexican part of the Yucatán Peninsula. After 3500 cal yr BP several paleoecological studies showed a marked tendency to drier climatic conditions. In pollen records, increased drought is expressed as a reduced presence of fossil arboreal pollen. Pollen records with the presence of Zea mays also show other taxa, which are indicators of disturbance in different vegetation types. Las actividades humanas han influenciado sobre los paisajes de la península de Yucatán desde más de 4000 años. Varios estudios paleoecológicos muestran actividades de agricultura, el registro polínico más antiguo de maíz (Zea mays L.) proviene del norte de Belice, con una edad aproximada de 3300 BC. Otros estudios paleoecológicos del norte de Guatemala y de la porción mexicana de la península de Yucatán muestran registros de maíz fósil con rangos de edad desde 1500 a 3000 A.C. La mayoría de los registros muestran una marcada tendencia a condiciones de mayor sequía después de los 3500 A.C. Estas tendencias de sequía se registran como reducción del polen fósil arbóreo. El registro polínico de Z. mays está acompañado de taxa que indican diferentes grados de perturbación en la vegetación natural. Keywords: Paleoanthropocene, Holocene, Yucatán Peninsula, fossil pollen, Zea mays. BOL. SOC. GEOL. MEX. 2018 VOL. 70 NO. 1 P. 49 ‒ 60 http://dx.doi.org/10.18268/BSGM2018v70n1a3 Manuscript received: October 12, 2016. Corrected manuscript received: April 26, 2017. Manuscript accepted: August 15, 2017. Palabras clave: Paleoantropoceno, Holoceno, península de Yucatán, polen fósil, Zea mays. The Paleoanthropocene of the Yucatán Peninsula: palynological evidence of environmental change Gerald A. Islebe, Nuria Torrescano-Valle, Alejandro A. Aragón-Moreno, Alejandro A. Vela-Peláez, Mirna Valdez-Hernández ABSTRACT The Paleoanthropocene of the Yucatán Peninsula: palynological evidence of environmental change The Paleoanthropocene of the Yucatán Peninsula: palynological evidence of environmental change INTRODUCTION 50 / Boletín de la Sociedad Geológica Mexicana / 2018 1. Introduction The Yucatán Peninsula has a long history of human impact and use, starting in the middle Holocene until the present, or Anthropocene. The interaction of human with natural forces has shaped the landscape of the Yucatán Peninsula on different scales and therefore offers a valuable opportunity of understanding past and present sustainability (DeClerk et al., 2010; Douglas et al., 2016; Ford and Nigh, 2016). The term Anthropocene was introduced by Crutzen and Stoermer (2000) to highlight the human influence on the environment and some researchers even proposed the term Palaeoanthropocene as the period of first anthropogenic change until the early industrial revolution (Foley et al., 2013). More specific to the area occupied by Maya culture and their influence on the environment, the term Mayacene was proposed to describe the period for the last 3000 years (Beach et al., 2015). In this paper we expand the idea of the Paleoanthropocene to the last 4000 years, as human impact on natural resources is evident in southern Mexico and Mesoamerica (Voorhies, 1996; Leyden, 2002) from this environmentally influential period. The human-environment-climate interaction goes back at least 4000 years, when early settlers became established and agriculture began transforming the landscape during the Archaic period. Abandonment of cities is strongly but not exclusively linked to climatic variability (Fedick, 2010; McNeil et al., 2010; Dunning et al., 2012, 2015; McNeil, 2012; Douglas et al., 2016), and several studies have highlighted Maya cultural development related to climatic events and environmental conditions using different proxies like isotope chemistry, sediment geochemistry and pollen (Hodell et al., 1995; Islebe et al., 1996; Kennett et al., 2012; Medina-Elizalde and Rohling, 2012). Opposing views on geographical determinism are ongoing in scholarly discussions, and it seems clear as a general consensus that the rise and fall of Maya culture is multifactorial. The periods of Maya cultural development are based on archaeology and are usually divided into Archaic (7000–2000 before Christ [BC]; Voorhies, 1996), Preclassic (2000 BC–250 AD), Classic (250–900 AD), and Postclassic and Contact periods (900–1500 AD; Coe, 1993; Webster, 2002; Dunning et al., 2015). This subdivision does not necessarily reflect environmental or climatic change in each period. Influence of Maya culture on the environment was reflected mainly in land cover changes, including deforestation in a broad sense, although there is ongoing discussion on the extent and relevance leading to culture demise and political breakdown (Aimers, 2007). This discussion includes different views, ranging from widespread forest reduction causing increasing aridity (Oglesby et al., 2010; Cook et al., 2012) to minimal forest cover loss due to adequate forest management (Ford and Nigh, 2009, 2016) and regional limited deforestation (Carrillo-Bastos et al., 2012), depending on the cultural period and climatic conditions. Climate variability is a key factor, mainly helping to explain precipitation variability in the Maya lowlands (Hodell et al., 1995; Dahlin, 2002; Medina-Elizalde and Rohling, 2012; Carrillo-Bastos et al., 2013; Douglas et al., 2016). The ancient Maya culture had profound knowledge of agriculture and forest management, and archaeological studies (Fedick, 2003) have shown transformation of wetlands for agricultural purposes with specific drainage channels. Others studies described the construction of terraces to reduce erosion and foster agricultural production (Dunning and Beach, 2000). Forest recovery after agricultural practices and climatic impact have shown that primary vegetation has a cycle of nearly 80 years (Mueller et al., 2010), and ancient Maya had a well-developed agroforestry system (Ford and Nigh, 2009). In this paper we summarize available published data on fossil maize (Zea mays L.) in pollen records from the Yucatán Peninsula, showing the first use of maize in agriculture, and the relationship with environmental and climatic change. Fossil pollen of corn (Z. mays) is an excellent proxy for human impact, as its presence provides a direct link bet (...truncated)