Discovery Magazine

Shifted Baselines: Quantifying Past Human Influences on Andean Landscapes

This research project will use paleoecology to investigate what is "natural" in the Andes. Bush's team will work in an area of very high biodiversity in the Peruvian Andes, where efforts to conserve Andean habitats to promote both biodiversity and carbon sequestration are being undertaken in a landscape that has been manipulated for millennia by humans. The high Andes is well-suited to paleoecology as there are large numbers of lakes that hold environmental records in their sediments. The investigators will use paleoecology to define "natural baselines" for ecosystems across a range of elevations, determining the natural height of tree line (important for above-ground carbon storage), and the trajectory of landscape change relative to climate change for the last 11,000 years. The researchers will analyze sediment cores from 10 lakes and 200 soil cores to provide the historical data to establish these natural baselines, and they will investigate how climate change interacted with human activity to produce altered fire regimes, crop use and forest cover. Paleoecology can, through analysis of fossil pollen and charcoal recovered from soils and lake sediments, provide detailed information about how systems have changed. The early Holocene climate (from roughly. 11,000 years to 9,000 years ago) was quite similar to that of today, but human populations in the Andes were very few. This period, therefore offers insights into the Andean ecosystem paleoecology without human activity.

The team will also look at records of climate change based on fossil pollen, diatoms and charcoal from lake sediments in the Galapagos where there has been no human influence until very recently. These records will provide a new high-resolution proxy showing periods of intense climate change. In the Andes, precipitation records derived from stalagmites will provide a longer time-series to assess variability of climate. Using these independently derived climate and vegetation data, the team will investigate whether paleoecology supports the concept of shifting baselines on a millennial scale.

Forming regional conservation policy with regard to local land use or even global carbon budgets requires an understanding of the trajectory of human influence on ecosystems. This project will provide new data on regional paleoecology, specifically the timing, extent and nature of human-induced change in Andean landscapes. It will also provide baseline data relevant to ongoing efforts to constrain the effects of climate change through carbon sequestration while conserving biodiversity. Collaborations with scientists in complimentary disciplines (soil science, plant physiology, ecology and remote sensing) will permit project results to be integrated into a larger prediction of appropriate policy for Andean conservation and for attempts to mitigate carbon release within Andean ecosystems.