Past, Present, and Future Climate Change: Can Palaeoecology Help Manage a Warming World? - Biodiversity Conservation and Environmental Change - page 101

Maximum, but over the timescales necessary for conservation planning, they proved robust
(Roberts and Hamann 2012).
A major modelling experiment has assimilated palaeodistribution data from the last Gla-
cial Maximum and MHA, and aims to develop and refine dynamic vegetation models that
accurately predict changes in biome distribution in the twenty-first century. The BIOME
6000 project integrates worldwide palaeovegetation data for the warmer conditions of the
mid-Holocene into a 6000 bp 'palaeobiome map' (Prentice et al. 2000, Harrison et al. 2014,
Bigelow 2003, Pickett et al. 2004). Known biome distributions are then be compared with the
outputs of coupled climate and biome models via the Palaeo-Modelling Intercomparison
Projects (PMIP1 and PMIP2). Future climate parameters can then be used to simulate distri-
bution changes over the coming century (Figure 5.8).
The 6000 bp and other modelling experiments suggest that arctic biomes will undergo
rapid changes in the course of the coming century. The boreal ecotone represents the north-
ern limit of forest cover, where tree extent is largely limited by temperature, and where a pre-
dicted approximate 2 degree rise in temperature is expected to drive the northward expansion
of boreal forests into tundra biomes (Kaplan et al. 2003). This has a direct impact on tundra
biomes but is also of concern because of vegetation climate feedbacks. In the mid-Holocene,
the northerly expansion of boreal forest in Canada and Eurasia reduced snow cover, which
lowered albedo and led to more heat absorption, exacerbating the warming effects of

MODELLING OF
MODERN AND 6000
BP BIOMES

6000 BP MAPS
FROM POLLEN
DATA

Monthly mean
temperature,
precipitation and
sunshine, soils,
hydrology,
photosynthesis,
stomatal behaviour,
competition between
plant functional types

Plants assigned
to Functional
Types

6000 BP Pollen
taxa assigned to
plant functional
types

Modelling of
modern plant
biome
distribution

6000 BP pollen
assemblages
assigned biomes
based on affinity
scores

Biome
assignments
validated using
modern pollen
data

Input of 6000 BP
climatic parameters

6000 BP
modelled biome
maps

6000 BP
Palaeobiome
Maps

Adjustment of
6000 BP model
parameters

Comparison of Modelled
Maps and PalaeoBiome
Maps

Figure 5.8 Structure of the Palaeo-Modelling Intercomparison Projects (PMIP), which simulate past
biome distributions based on plant functional types and environmental/ecophysiological parameters.
Results are compared to known biome distributions from the fossil pollen record.