As much as the weather has been spectacular the past two months, there could be a dark side to all this sun. Brown pastures, shrinking or disappearing streams, low river levels, and powdered earth are the hallmarks of a seasonal drought that has caught everyone off guard. People love this weather but what’s going on here…?
The weather stats for September are amazing. According to our guy Roger Pannett, volunteer weather observer for Environment Canada, “Overnight on September 10th/11th, a fast moving cold front produced a meager 6.6 mm rainfall, 5.86 per cent of the average monthly rainfall. Consequently it was the driest September in more than 133 years! With a total August and September rainfall of only 7.8 mm compared to the average 177.5 mm it was the driest since records started in 1879. The previous lowest rainfall for the same period was 31.5 mm in 1915.”
Pannett said that, for the fourth consecutive September, mean temperatures were above normal, equalling the trend first recorded from September 1973 to 1976. On September 8th the temperature broke records at 31.8C, which was a huge 10.5oC above normal. The mean maximum for the month was 24.73C compared to the 30-year average of 21.0C. In fact, the 2012 summer (July to September) was the 12th consecutive summer with above normal mean temperatures, a trend never previously observed since Chilliwack temperature records started in 1895.
If this warm trend continues in the coming years, we may see profound changes in natural food sources such as fish, birds, and ungulates. Only last week, UBC fisheries scientists reported in the journal Nature Climate Change that increasing ocean temperatures and decreasing oxygen levels could lead to fish shrinking in size by as much as 14 to 24 per cent in the next 40 years. That’s huge!
There is a rule of nature known as the Bergmann’s rule that mammals in a warmer climate rid themselves of body heat more efficiently with a smaller body size while animals in cooler climates have a larger size to retain heat and keep warm.
The trend has been observed in the evolutionary record as far back as 56 million years ago when the first horses evolved. They were about the size of a small dog. But their appearance coincided with a global warming phase when temperatures increased by about 10C over a period of about 130,000 years. The horses shrunk to about the size of a house cat. Then as the climate cooled during the next 45,000 years, they grew larger and continued their evolution over millions of years to become today’s familiar horse. On the plus side, they had time to adapt as global temperatures warmed and then decreased.
But what about now?
Rapid global warming could trigger a tendency toward smallness in many mammals, fish and birds, some of them food resources. Ornithologists are already reporting a tendency toward smallness in some bird species. The problem is, an increase in global temperature could happen much faster than past evolutionary curves. So can animal species adapt or are some going to face an extinction event? The disappearance of species means changes in the biodiversity of habitats that can put stress on all those in the network of things.
Meanwhile, animals struggle to follow their instincts despite the stresses. The water’s warm, the streams are low and spawning salmon have held back in the ocean for as long as they could.
“Spawning’s like going to the bathroom,” said Chris McCunn with Fred’s Custom Tackle. “You hold off as long as you can. But when you’ve gotta go, you’ve gotta go. Now the fishing’s great!”
If only we were sure that would last…