Barrie Creeks, Lovers Creek, and Hewitt's Creek Subwatershed Plan

The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatershed Plan
looking for opportunities for outdoor recreation. Further, as development proceeds, accessible
upland natural areas may become even rarer, concentrating this pressure into increasingly rare
remnant habitats. As a result, as development proceeds, the need to manage the impacts
associated with outdoor recreation will only intensify.
6.3.9 Climate change
Projections suggest that climate change will have significant impacts on terrestrial natural
heritage features in the Lake Simcoe watershed. Recent modeling work was completed for the
Lake Simcoe watershed, examining the response of tree species to climate change, as
influenced through factors such as the current range of the species, its current local abundance,
phenology, and seed production (Puric-Mladenovic et al., 2011). As climates change, the model
predicts that balsam fir (Abies balsamea), red maple (Acer rubrum), American beech (Fagus
grandifolia), yellow birch (Betula alleghaniensis), white cedar (Thuja occidentalis) and eastern
hemlock (Tsuga canadensis) will all exhibit slight decreases in their occurrence in the forests of
the Barrie Creeks, Lovers Creek, and Hewitt’s Creek subwatersheds. In fact, the projected
shifts in climate may cause some species which are currently relatively widely distributed to
become more narrowly restricted to remaining habitat, including red maple becoming restricted
to wetlands, as they shift to areas with moister soil, and yellow birch becoming restricted to
ravines, as they shift to areas with cooler and moister microclimate. Other species, notably red
oak (Quercus rubra), are anticipated to become more common as a result of the warming
climate.
Modeling results suggest that forests in cooler microclimates in ravines and north facing slopes,
which tend to have a relatively high dominance of eastern hemlock, yellow birch, and American
beech, may be among the most sensitive ecosystem to the changing climate. Sadly though, the
species which the model suggests are the most vulnerable to climate change are those which
we think of as being proto-typically Canadian. Both sugar maple (Acer saccharum) (Canada’s
national symbol), and white pine (Pinus strobus) (Ontario’s provincial tree) are predicted to
experience severe declines in the Barrie Creeks, Lovers Creek, and Hewitt’s Creek
subwatersheds (Puric-Mladenovic et al., 2011).
A separate set of models, developed to assess the vulnerability of wetland ecosystems, suggest
that a ‘worst case’ climate change scenario would have catastrophic impacts on wetlands in the
Lake Simcoe watershed. The increases in average annual temperature and decreases in
average annual precipitation projected to occur by the year 2100 is estimated to make 90% of
the swamps and 84% of the marshes in the Lake Simcoe watershed vulnerable to drying. As
drying occurs, it is expected that marshes would shift in composition to become swamp (or
thicket swamp) type communities, and treed swamps would shift to become mesic forests.
Interestingly however, these same models suggest that the swamps and marshes in the Barrie
Creeks, Lovers Creek, and Hewitt’s Creek subwatersheds will be more resilient to projected
changes in climate, due to the role of ground water discharge in maintaining these wetland
features (Chu, 2011).
In sum, these models suggest that there will be a shift in community composition in the natural
areas in the Barrie Creeks, Lovers Creek, and Hewitt’s Creek subwatersheds, and a net loss of
tree species diversity. Unfortunately, natural areas lacking in biodiversity tend to be more
vulnerable to other threats such as insects, disease, and invasive species, suggesting that the
impacts seen to terrestrial natural heritage features may become cumulative in nature.
This loss in native tree species diversity may be mitigated somewhat by the ability of species
not currently found here to thrive in the expected new climate. Species found in southern
Chapter 6: Terrestrial Natural Heritage 295