Changes in fire regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data

Abstract

Knowledge of historical fire activity tends to be focused at local to landscape scales with few attempts to examine how local patterns of fire activity scale to global patterns. Generally, fire activity varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesised sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In eastern and western North America and western Europe and southern South America, charcoal records indicate less-than-present fire activity from 21,000 to ~11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greaterthan-present fire activity from ~19,000 to ~17,000 cal yr BP whereas most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ~13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8000 to ~2000 cal yr BP, Indonesia from 11,000 to 4000 cal yr BP, and southern South America from 6000 to 3000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the postglacial period. These complex patterns can be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.

A continuous record of fire covering the last 10,500 calendar years from southern Sweden — The role of climate and human activities

“…The concept of a "fire regime" usually include parameters such as fire intensity, fire strength/depth in the humus layer, frequency and spatial size (Conedera et al, 2009). In the following discussion we refer to "fire activity" following the definition of Power et al (2008). However, we also discuss "fire regimes" at a century to millennial temporal scale, a "fire regime" being in that case defined by the frequency of major fire episodes (including one to several "fire events") despite the fact that the time resolution of the analyses is not high enough to allow inference of detailed fire frequencies at decadal scales.…”

“…Such changes can be studied over a variety of temporal scales using records of charcoal in lake sediments or peat deposits (e.g. Power et al, 2008). However, full understanding of the effects of climate change on fire activity at the regional to local spatial scale, and the consequences on vegetation and fauna, still requires detailed reconstructions of fire history over the last millennia in many parts of the world.…”

“…Tinner et al (1999) suggested that increased fire in the Alps for the period 7000-5000 cal yr BP resulted from the combined effects of intensified land-use activities and centennial-scale shifts to warmer and drier climatic conditions. A comprehensive discussion and synthesis of the long-term climate forcing on past fire activity is found in Power et al (2008). Charcoal records in Europe indicate fire activity greater than present during the early Holocene (6500-4500 BC) and the late Holocene (1000 BC-AD 1500), and fire activity lower than present during the middle Holocene (4500-1000 BC).…”

“…Fires during the late Holocene in Europe and western Asia are generally explained by the use of fire as a tool for deforestation during the Bronze Age and Iron Age. In the Northern Hemisphere, increased seasonality and biomass may have regulated the early Holocene fire regimes, whereas decreased seasonality, coupled with increased human activity, were important regulators of fire during the late Holocene (Power et al, 2008).…”

Vegetation and fire history since the last glacial maximum in an inland area of the western Mediterranean Basin (Northern Iberian Plateau, NW Spain)

“…This situation was widespread over the entire Iberian Peninsula (Carrion and van Geel, 1999;Carrion, 2002;Connor et al, 2012) and the rest of Europe (Power et al, 2008).…”