Determining Long-Term Ecological Baselines in the Tropical Andes

Castillo, Bryan Guido Valencia (2014). Determining Long-Term Ecological Baselines in the Tropical Andes. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000eff3

Abstract

Conservation, restoration and management strategies are employed to maintain Earth’s biological diversity and environment to a near “natural” state. But “natural” has included degraded landscapes.

The tropical Andes is a hotspot identified as a global conservation priority because of their high biodiversity, and threat to ecosystems by human activity and climate change. Our understanding of long-term (100-1000’s year) natural ecological baselines is limited due to a paucity of studies in the Andes. In this thesis ecological baselines are identified for tropical Andean vegetation by comparing multi-proxy palaeoecological reconstructions (pollen, diatoms, charcoal, loss-on-ignition and magnetic susceptibility) derived from three lakes; Miski, Huamanmarca and Pacucha. These sites experience different levels of human impact today; Miski and Huamanmarca are undisturbed, Pacucha is disturbed.

The trajectory of vegetation change at the three lakes over the last c. 12ka was determined, and compared, using Detrended Correspondence Analysis of multi-proxy data. The sites share a similar trajectory of vegetation change prior to c. 7 ka. After c. 7 ka Pacucha diverges from the other sites due to anthropogenic disturbance. Therefore natural ecological baselines for the tropical Andes can be determined from undisturbed sites from the last 3-2 ka, and disturbed sites from the last c. 10 ka.

Fossilized tree pollen from across the tropical Andes was then used to test the hypothesis that, prior to human disturbance woodlands (dominated by Polylepis) formed a continuous ‘belt’ from Ecuador to Bolivia. A MaxEnt model based on 22 modern environmental variables and data derived from 13 Andean records were used to determine the spatial arrangement of Polylepis woodlands and suggests that they can naturally occur as a mosaic. The palaeoecological reconstructions confirmed that woodland mosaic predates human arrival (c. 14 ka) and disturbances (c. 7 ka). After c. 7 ka, human disturbances further accentuated the woodland patchiness generating a hyperfragmented landscape.