Forest Investment Account (FIA) - Forest Science Program
FIA Project Y091120

    Future vegetation structure and vertebrate distributions based on changes in moisture balance and temperature
Project lead: Bunnell, Fred (University of British Columbia)
Contributing Authors: Bunnell, Fred L.; Wells, Ralph W.; Hebda, Richard J.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Climate change will have profound effects on the flora and fauna of British Columbia (Hebda 1997; Bunnell et al. 2005, Hamann and Wang 2006). This project anticipates those effects and describes them well enough that forestry and other land use practices can respond to them and potentially mitigate and adapt to them. It builds on existing work (e.g., ibid., by improving our ability to project both vegetation and vertebrate response to changes in climate and by describing management responses most likely to reduce impacts. The project addresses two major forest management issues: 1) how are the broad patterns of community structure likely to change and how should silvicultural planning and practice respond, and 2) how is the capacity of the environment to sustain biodiversity likely to change and how should management practices respond. This latter issue is of direct interest to First Nations. This proposal covers the first year of a 3 year project and emphasizes acquiring and compiling data sets and developing, evaluating and refining models.

This project improves the projection of climate change impacts for BC by incorporating influences of evapotranspiration and moisture stress more effectively into existing models. It develops a moisture balance model useful at provincial scale and calibrates biodiversity attributes such as vegetation structure, distribution of modern wetlands and vertebrate species to moisture balance data. The patterns are then projected into future using climate model data. Plant community structure (physiognomy) rather than composition is the focus, because structure is well linked to climate (Stephenson 1990) and vertebrate distribution (Bunnell et al. 1999). . Greater confidence can be developed around changes in vegetation form (such as the proportion of deciduous to coniferous species) than for each of the many species comprising the vegetation.

To more accurately predict vegetation responses we will evaluate and develop a moisture balance model (e.g. Thornthwaite, Penman-Monteith) and create a map with particular focus on intensity and length of the summer dry season. Moisture balance data will be related to vegetation (eco-plot) data available from Ministry of Forests, including where possible wetland types. Using data of future climatic conditions from climate models available through the Pacific Climate Impacts Consortium (PCIC), a range of future vegetation structure and wetland distribution patterns will be developed and using GIS displayed on maps.
Integration of the projected changes of climate, vegetation and vertebrates examines two broad but related issues: 1) simple landform responses at local scales, and 2) responses to vegetative structure more broadly. Two broad geometric responses are evident locally. The first results from the broadly conical shape of mountains: a linear increase in temperature reduces the amount of alpine habitat at a rate much greater than linear. There likely is little that can be done to reduce this impact, though its consequences can be broadly described. The second geometric impact results from the convex shape of ponds, lakes and wetlands. Again, a linear increase in evaporation reduces the area of suitable habitat at a rate more rapid than linear. That is particularly true of species reliant on emergent plants that have a narrow rooting zone. In this case, some mitigation may be possible by water management targeted to areas where effects are anticipated to be most profound or management efforts most likely to succeed.

Broad-scale responses to vegetative structure are most complex for migratory species. Birds, however, are the richest group of vertebrates and must be accommodated. The general model of bird response proposed by Bunnell et al. (2005) uses migratory categories as its major feature, and predicted the direction of response accurately in about 70% of cases for the few species that could then be tested. We will refine that model in a fashion that should allow prediction of: changes in arrival and departure dates, changes in numbers over-wintering, range expansion, shifts in relative density within the province, and dates of clutch initiation. A major goal of this project is to refine the model of general response and to test it over a broad range of bird species. That model makes predictions based largely on temperature. An obvious extension facilitated within this project is to include moisture more directly and to incorporate anticipated changes in vegetation structure.

As the richest group of vertebrates, birds again provide the most fertile opportunities for testing: some species are strongly associated with hardwoods, others with conifers, some are near-obligate shrub nesters, others strongly associated with grasslands or with wetlands of different forms. The links between climate, the moisture balance-vegetation data base, and vertebrates is strong. Although the first tests among vertebrates will be made using bird species, there are clear extensions to amphibians, some reptiles and mammals as well. The approach provides the
potential to relate the response of the biota to changes in moisture and temperature resulting from climate change in general.

The future distribution and abundance of vegetation and selected vertebrate species (initially birds) will be derived from projected climate and displayed on maps. The maps will show the character and extent of likely changes and help reveal potential impacts on silvicultural practices, and provide insight into adaptations to these for sustaining efficient forestry, and biodiversity. The magnitude, rate and location of change can help guide the choice and location of proactive measures to help sustain biodiversity.

Bunnell F.L. et al. 1999. Managing to sustain vertebrate richness in forests of the Pacific Northwest: relationships within stands. Environmental Reviews. ? Bunnell, F.L., K. A. Squires, M. I Preston, and R. W. Campbell. 2005. Towards a general model of avian response to climate change. Pp. 59-70 In Implications of climate change in BCs southern interior forests. Columbia Mountains Institute of Applied Ecology. URL:
? Hamman, A., and T. Wang 2006. Potential effects of climate change on ecosystem and tree species distribution in British Columbia. Ecology 87: 2773-2786. ? Hebda, R.J. 1997. Impact of climate change on biogeoclimatic zones of British Columbia. In Taylor, E. and B. Taylor. Responding to Global Climate Change in British Columbia and Yukon: Volume 1 of the Canada Country Study: Climate Impacts and Adaptation. Environment Canada and British Columbia Min. of Environment, Lands and Parks. Vancouver and Victoria. pp 13:1-15. ? Stephenson, N.L. 1990. Climate controls of vegetation distribution: the role of water balance. The American Naturalist. 135 (5): 649-670.
Related projects:  FSP_Y102120FSP_Y113120


Executive summary (41Kb)
Progress report - Assessment of vulnerability of wetlands to climate change (0.3Mb)
Progress report - Associations of vertebrates with broad habitat types (0.1Mb)

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Updated April 29, 2011 

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