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

The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatershed Plan
Ontario (such as black maple [Acer nigrum]) or the southeastern US (such as black hickory
[Carya texana]) may become relatively common in forests in these subwatersheds, further
influencing the shift in plant community composition. However, the fragmented nature of the
landscape that these species would need to cross will no doubt limit their ability to colonize
forest remnants, without assisted migration (i.e. planting) (Puric-Mladenovic et al., 2011).
Other, less desirable, species may also be able to respond positively to changing climates as
well. Some invasive species are projected to experience a northward range expansion (e.g.
Kudzu [Pueraria lobata], an extremely invasive vine), or experience increased growth rates and
biomass (e.g. Eurasian water milfoil [Myriophyllum spicatum], a widespread invasive aquatic
plant) (Sager and Hicks, 2011).
Predicted impacts of climate change on wildlife are less clear. Some authors (e.g. Walpole and
Bowman, 2011) suggest that as average annual temperature increases, more species of both
birds and mammals will be able to inhabit the Lake Simcoe watershed. Others caution that, for
some species, the disadvantages of climate change may outweigh the advantages. For
example, wetland-dependent species may suffer significant population declines as wetlands dry
up (Chu, 2011). Similarly, although some migratory birds have been able to take advantage of
warmer springs and are migrating earlier, other species appear less able to adapt their
behaviour to changing temperature and are vulnerable to being unable to find sufficient food
resources or suitable nesting sites later in the season (Burke et al., 2011). These relationships
may be even more complicated in these subwatersheds however, as the interacting effects of
climate change, landscape fragmentation, and urbanization may constrain the ability of wildlife
to colonize habitat areas, and to persist within them.
Key Points – Factors Impacting Terrestrial Natural Heritage - stressors
• There are multiple stressors to natural heritage systems in these subwatersheds,
many of which interact.
• Over the short term, the greatest impact to natural heritage values is expected to be
due to changes in land use. These impacts can only be expected to increase as the
population, and thus the developed area, in these subwatersheds increases.
• In addition to the direct loss of natural areas, development is typically associated
with an increase in roads (which can cause mortality in wildlife and disturbance to
remaining nearby natural areas), an increase in impervious surfaces (which can
affect the hydrology of remnant natural areas), and the loss of natural habitat along
shoreline and other riparian areas (which tend to be disproportionately important to
wildlife).
• Remnant natural areas in heavily settled landscapes typically face more intense
stresses as well, including an increase in the number and diversity of invasive
species, increased pressure from recreational users, and trophic cascades caused
by changes in food webs and other inter-species relationships.
• The emerging threat of climate change will interact with all of these threats, creating
additive long-term stresses on natural areas and wildlife populations. Although
research in this area is still emerging, initial predictions suggest a loss of wetlands
and wetland-dependent species, and a loss of some of our most-loved species of
native trees.
Chapter 6: Terrestrial Natural Heritage 296