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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Abstract
	The profound climatic and physical changes predicted as a result of 
the "greenhouse effect" may have major impact on British Columbia's 
vascular plants and vegetation.  Potential warming of 2ūC-4ūC, reduction 
of summer soil moisture by 30-40%, and a rising seal level from 0.5-1.5m 
could strongly alter or eliminate major vegetation types and lead to 
expansion or shrinking of species ranges and in extreme cases extirpation 
of species.  The relatively warm and dry interval between 10,000 and 6,000 
years ago provides an analog for predicting the impact and global 
warming.  Alpine zones may shrink significantly as timberline rises 
possibly as much as 100-200 m.  Species areas will be reduced, populations 
will become isolated, and some species may be lost.  Small alpine and 
subalpine patches in the south are at greatest risk.  Wetlands will change 
in character, and shrink. Hydrological gradients will change and there 
may be a shift from acidic bog-wetlands and species to neutral or even 
alkaline fens and marshes and species.  Demand for water by people will 
increase and further stress wetland habitats.  Major vegetation 
adjustments will occur in the dry interior where grassland communities 
may expand up-slope and northward.  Grassland area may increase 400%, 
and grassland communities may become vertically differentiated. Arid 
habitat species, including rare taxa, may become more abundant and 
widespread providing there are migration corridors.  Sea levels will rise 
and drown estuaries.  The size of confined estuaries will be severely 
reduced and rare species may disappear.  Forest composition and extent 
will change as species respond individually and re-assemble into new 
forest types.  Weedy, adventive species will likely expand and become 
permanent elements of new vegetation types. In general, impacts on plant 
populations will likely be sudden, precipitated by extremes of climate.
	Recommendations include:  1.  a long-term project to inventory, 
study the biology of, and monitor the flora, especially rare species,  2.  
protection of populations and areas of concentration of rare plants as 
reservoirs of raw material for future vegetation types,  3.  Conservation of 
ecological gradients for future dispersal.  4.  Paleoecological studies to 
provide predictive data.

Introduction

	The richest, vascular flora in Canada, that of the province of British 
Columbia, comprising about 2 500 species (Straley et al. 1985) may be at 
great risk.  In the next 50-100 years the profound climatic and physical 
changes predicted by many experts as a result of the "Greenhouse Effect" 
can be expected to significantly affect this native flora.
	In this paper, I will briefly outline the expected climatic and 
physical changes resulting from anticipated global warming, and how 
these might directly impact the native flora.  I will focus on four major 
ecosystems liable to change dramatically:  the alpine (cf. Alpine Tundra 
Biogeoclimatic Zone of Krajima et al. 1982); wetlands; interior grassland 
and sagelands (cf. Ponderosa Pine Biogeoclimatic Zone and Bunchgrass 
Biogeoclimatic Zone; Research Branch 1988) and marine shoreline 
vegetation.  I will note some rare or threatened species potentially at risk.  
Then I will propose some future strategies to soften the potential impact of 
global change on the native flora.