GLOBAL CHANGE AND BRITISH COLUMBIA NATIVE FLORA
Richard Hebda
Botany Unit
Royal British Columbia Museum
Victoria, B.C.   V8V 1X4
Presented at the "British Columbia Native Plants, their current Status and 
Future
Colloquium at Botany Dept., University of British Columbia, May 12, 1990
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Forests
	Before moving to general comments and summary I will briefly 
address the impact of global warming on forest vegetation.  The 
distribution of tree species will change.  Paleoecological studies have 
shown that species will behave individualistically, so there is no guarantee 
that we will see the same forest types as occur today.  The forest types on 
valley sides in the south will likely get squashed together on the upper 
slopes.  In arid regions of central and southern B.C. we can expect:  1)  
Reduction of lowland forests and expansion of upland forests;  2)  General 
northward migration of forest zones, and gradually increasing change in 
their structure;  3)  Increasing fire frequency and the predominance of 
seral lodgepole pine forests, especially in central B.C.  (see Mathewes 
1985). 
	The new equilibrium forests will not be the same as the forests 
today. Some species such as moisture-requiring western red cedar, will 
have a diminished role in forests.  It is only in the last 5 000 years that this 
species has become a major forest element (Hebda and Mathewes 1984).  
Forest change may not be gradual.  In the Victoria area, during the 
relatively droughty summer of 1988, large healthy cedar trees died, 
presumably because of an insufficient supply of nutrient-rich water.  
Episodes of extreme climate (drought) will likely eliminate some species 
from large parts of their range.
	An important point to consider is the organic content of the forest 
soil. Large organic deposits in moist forests serve to cool the soil, reduce 
moisture loss and erosion and to store carbon.  The organic-rich soils must 
be protected from disruption and desiccation as much as possible.  They 
will act to moderate climatic effects, moderate the release of carbon 
dioxide and help slow the rate of change of vegetation and species 
distribution.  From a practical perspective this might mean treading as 
lightly as possible when logging an area, and perhaps leaving a partial 
canopy (selective logging) to protect the organic component of the soil 
from decomposing or eroding.