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Effects of Climate on Numbers of Northern Prairie Wetlands

Results: Effects of Changing Temperature and Precipitation


The effect of increasing temperature on number of wet basins was not consistent among the three regions (Table 2). Temperature had the greatest affect in the parkland; an increase of 3 °C resulted in a 56% decline in the average number of wet basins. Canadian grassland was least affected, showing a 15% decline; United States grassland was intermediate with a 28% decline in average number of wet basins. Increasing temperature by 6 °C in the parkland resulted in five years with a predicted average of zero wet basins (Figure 3). The same increase in temperature had a less dramatic effect in the grassland areas of Canada and the United States; numbers of wet basins declined, but the average never fell to zero. During nearly half of the period 1973-1987 a greater percentage of basins held water in the parkland than in United States grassland (Figure 4). Under the scenario of increased temperature, wetland conditions in the parkland are projected to be better than in the United States grassland in only three of the 15 years simulated.

A 10% increase in precipitation alone resulted in a uniform increase in percentage of wet basins throughout the regions studied (Table 2). Parkland wet basins increased by 11%, whereas wet basins in the United States and the Canadian grassland increased by 12%. The 10% increase in precipitation compensated for some of the effect of increased temperature, but results varied by region (Table 2). In the Canadian grassland, a 10% increase in precipitation nearly balanced a 3 °C increase in temperature. Parkland wet basins still declined by 39%, while United States wet basins declined 12% from the current average conditions.

Decreasing precipitation alone by 10% resulted in roughly similar declines in wet basins among the three regions (Table 2). When decreased precipitation was examined in concert with a 3 °C temperature increase, the models again revealed the heightened sensitivity of wetlands in parkland to temperature compared with wetlands in grasslands: parkland wet basins declined by 74%, compared with 31% and 56% declines in Canadian and United States grassland wet basins, respectively (Table 2).


Table 2. Model projections for increased temperature and precipitation.

Model Area Mean percent wet basins/year (percent change in parentheses)
Observed
1974- 1987
+3C +6C +10% precip. +3 C and +10% precip. -10% precip.
+3 C and -10% precip.
Parkland51.522.4
(-56)
4.5
(-91)
57.2
(+13)
31.2
(-38)
36.3
(-28)
13.4
(-74)
Canadian Grassland49.242.0
(-15)
35.1
(-29)
55.0
(+12)
38.9
(-21)
38.9
(-21)
34.1
(-31)
United States Grassland51.4 36.4
(-28)
22.8
(-56)
57.8
(+12)
38.2
(-26)
38.2
(-26)
22.8
(-56)

gif -- Line Graph

Figure 3. Yearly estimates of percentage of basins holding water for current climate (red line) and climate with a 6 °C increase in temperature (blue line) in parkland, Canadian grassland, and United States grassland.

gif -- Line Graph

Figure 4. Comparison of percentage of basins holding water in parkland (red line) and United States grassland (blue line) for current climate and climate with a 3 °C increase in temperature.

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