Fire, climate change and human impact in tropical ecosystems: paleoecological insights from the East African region

Fire is an important ecological factor of disturbance in African tropical ecosystems, driving vegetation dynamics and regulating nutrient cycling and biomass. The significance of wildfires for future environmental processes is underlined by recent projections of global warming, which predict more frequent and more intense extremes of natural events. Particularly in East Africa, where population growth and natural resource exploitation are among the highest in the world, strategies for sustainable economic development will have to deal with environmental changes at regional to continental scales. Understanding such complex responses to global change requires long-term records, since only they provide a way to observe the response of ecosystems to large-magnitude environmental change on decadal and longer time scales.

Keywords: tropical fire ecology, forest management, East Africa, climatic change, Holocene, fire history

We use high-resolution charcoal data from lake-sediment cores to reconstruct past fire/climate/human interactions in East Africa, aiming in particular

  1. to understand how the fire regime influenced vegetation dynamics during the last millennia in savannah-type and sub-humid tropical ecosystems,
  2. to test whether changes in fire regime are coupled with episodes of past climatic extremes inferred from the available sedimentological data, and
  3. to detect early human deforestation and the timing of increased fire frequencies beyond its natural variability.

Additionally, we will apply novel techniques such as molecular markers (benzene polycarboxylic acids, BPCAs) to complement the standard sedimentary approaches to reconstruct Holocene fire history. The proposed research addresses new, highly relevant questions for today's key issue of sustainability (economic development, natural resource management, adaptation of vulnerable communities to global change). Additionally, it will contribute with new high-quality data to ongoing multi-proxy research concerning the magnitude, frequency, and rates of past climate change in equatorial East Africa. Finally, the project will contribute to our understanding of tropical ecosystem functioning and its interaction with regional, cultural, and economic systems.

investigated sites
Location map of the investigated sites in East Africa

a) Rainfall Estimation (RFE), showing a W-E precipitation gradient (modified from NOAA's Climate Prediction, U.S. Geological survey)
b) current land use
c) NDVI index (Normalized Difference Vegetation Index, dark green=tropical forest and light green=savannah)

Vegetation cover and fire activity
Vegetation cover (NDVI index, green) and fire activity (red) along a S-N transect through Africa, in early spring 2010.

Fires increase at the tropical forest/savannah interface (modified from NEO - Nasa Earth Observation).

Funding

This is an "Ambizione" program funded by the Swiss National Science Foundation (Project no. 126573).

Participants

Internal

Daniele Colombaroli, Willy Tinner

External

Dirk Verschuren (University of Ghent), Feng Sheng Hu (University of Illinois), Michael Schmidt and Samuel Abiven (University of Zuerich)