Vegetation history in western Uganda during the last 1200 years: a sediment-based reconstruction from two crater lakes

Immaculate Ssemmanda, David B. Ryves, Ole Bennike, Peter G. Appleby

Research output: Contribution to journalArticleResearchpeer-review

44 Citations (Scopus)

Abstract

Pollen, plant macrofossil and charcoal records from two neighbouring crater lakes (Lake Wandakara and Lake Kasenda) in lower montane (altitude ∼1200 m) western Uganda (0.5°N, 30°E) reveal major changes in local and regional vegetation over the last 1200 years, which can be related to regional variations in climate (especially effective precipitation) and human impact. The biological signals are supplemented by evidence from physical sedimentary analyses (magnetic susceptibility, loss-on-ignition, dry mass accumulation rate) for major catchment changes in a wider regional context. From AD 750 to 900, medium-altitude moist forest existed around Lake Kasenda, which was largely replaced by grassland by AD 1000, coincident with evidence for increased catchment erosion and fire events, linked to human impact during a brief arid phase. Despite wetter conditions from AD 1000 to 1200 and in the 1400s, grassland prevailed around both sites until c. AD 1700-1750, with increased catchment disturbance from AD 1600 to 1700, shortly before the abandonment of major regional settlements and a switch to dispersed homesteads more reliant on pastoralism. Both sites show the return of semi-deciduous and swamp forest from c. AD 1700 to 1800, with tree and shrub pollen remaining high until the most recent times. Pollen assemblages reveal increasingly clear human impact on local and regional vegetation in the twentieth century, which obscures any climate signal. Pollen signals may not be sensitive to all climatic fluctuations (e.g., late eighteenth-early nineteenth-century aridity), but appear to record the varying impacts on vegetation communities of both climate and human activity over long timescales. Other proxies should be analysed to disentangle further the relative importance, and interactions, of these two major drivers of environmental change in tropical Africa in recent millennia.

Original languageEnglish
Pages (from-to)119-132
Number of pages14
JournalHolocene
Volume15
Issue number1
DOIs
Publication statusPublished - Jan 2005

Keywords

  • Charcoal
  • Climate change
  • Crater lakes
  • East Africa
  • Human impact
  • Late Holocene
  • Macrofossils
  • Pollen
  • Uganda

Programme Area

  • Programme Area 5: Nature and Climate

Fingerprint

Dive into the research topics of 'Vegetation history in western Uganda during the last 1200 years: a sediment-based reconstruction from two crater lakes'. Together they form a unique fingerprint.

Cite this