Biodiversity

The Alberta-Saskatchewan Cypress Hills

Climate change may exceed land use change as the dominant factor causing change to biodiversity and ecosystems within Saskatchewan. Increasing growing season aridity is the single most important ecosystem impact and also represents a major biodiversity management challenge. Changes in climate will alter environmental conditions to the benefit of some species, and detriment of others, often with economic consequences. As vegetation and animals shift in response to changing climate, tourism and recreation activities and agricultural, forestry and urban pest management practices will have to adjust.

Main Causes of Biodiversity Loss:

• invasive exotic species
• overuse/exploitation of species
• pesticides and pollution
• climate change
• habitat loss and fragmentation - i.e. land use change

Key Climate Change Factors:

Climate variability is increasing. This means that not only is “average” climate changing, but that incidence of extreme climate events, i.e. deviations from average climate, may increase in frequency and duration. Such events can have major ecosystems impacts.

Impacts:

Boreal Forest

• The boreal forest is expected to be significantly affected by climate change (e.g. changes in species composition), especially at its southern boundary where tree growth is typically moisture limited.
• Native conifers will be significantly impacted by increasing aridity and will decline in the southern parts of their current range, while the boreal hardwoods, in particular aspen, may prove more robust and more able to persist in their traditional ranges.
• In water-stressed forest regions there will be a general reduction in tree growth, regeneration failure in dry years, a gradual reduction in tree cover, and expansion of grassland patches.
• Increased average winter temperatures will lead to greater overwinter survival of pathogens and increased disease severity.
• Drought conditions weaken trees' defences to more virulent pathogens.
• In the northern boreal region, however, where the growth limitation is heat, a warmer climate may increase productivity and tree growth.

Prairie Parkland

• Prairie-parkland parks can expect increases in forest fire frequency and intensity, increased forest disease outbreaks and insect infestations, and loss of boreal forest to grassland and hardwood forest

Island Forests

• As they are relatively small ecosystems, island forests (such as Duck Mountain or Cypress Hills forests) are vulnerable to climate change. They may suffer increased pathogen attack, and forest decline.

Vegetation Zonation

• Models of vegetation zonation have shown a northward shift of the forest-grassland boundary with climate change
• New landscape ecosystems might evolve; for example, a drier climate in southern Saskatchewan could potentially support shortgrass prairie currently found farther south.

South Saskatchewan Vegetation Zonation Under Climate Change

Figure #: Vegetation zonation in southern Saskatchewan as predicted by ecoclimatic models (Vandall et al. 2006). The upper map shows the zonation resulting from 1961-90 climatic normals. The lower map shows the predicted zonation resulting from the HadCM3 B21 scenario for the 2050s.

Vandall et al. (2006) modelled the shifts in Saskatchewan vegetation zones resulting from three climate change scenarios for the 2050s. Results for one of these scenarios are shown above (all scenarios gave similar results).

Most of the boreal forest up to 54° latitude is replaced by aspen parkland. Most of the aspen parkland is replaced by mixed prairie. Most of the Canadian mixed prairie is replaced by U.S. mixed prairie (i.e. the kind of mixed prairie found in Montana, Wyoming and the Dakotas). The driest area, in southwestern Saskatchewan, shifts to shortgrass prairie, currently found from Colorado southward.

Waterfowl

The prairie pothole region of central North America is the single most productive habitat for waterfowl in the world, with the Canadian Prairies producing 50% to 80% of the Canadian duck population. As a long-run trend, increasing aridity in the prairie grasslands is likely to negatively impact migratory waterfowl populations as waterfowl numbers decrease in response to drought and habitat loss.

Aquatic Species

• Some prairie aquatic species are at risk of extirpation, as warmer and drier conditions stress aquatic ecosystems.
• Larger algal blooms, accelerated eutrophication, and serious impacts on fish species are expected, due to a combination of climate change, increased nutrient runoff, and increasing human use pressures on natural water systems.

Adaptation Options:

• Boreal and Island Forests:
  • Consider more intensive management practices to preserve some type of forest cover including maintaining a diversity of age stands, responding aggressively to pathogen disturbances and regenerating the forest with non-native tree species that are better adapted to new climate parameters. Test plantations of native and non-native tree species are advisable.
• Protected Areas:
  • Investigate potential to increase connectivity between protected areas to facilitate migration of species populations. However, increased connectivity may also hasten the decline of some ecosystems by favouring alien invasions.
  • Change conservation management to build resilience into ecosystems rather than seeking stability.
  • Selection of protected areas may need to focus on site heterogeneity and habitat diversity (as these provide some buffer against climate change) rather than on representativeness
• Manage other biodiversity pressures so far as possible, such as habitat loss, as biodiversity pressures are cumulative.