Farmers like Bill Zylmans are often the first to notice subtle changes in annual weather patterns.

He owns one of the largest potato farms in Western Canada, W&A Farms in Richmond B.C., and says he's noticed the growing seasons are becoming shorter.

"Spring starts a little later so it's wetter longer, so we've had to reduce our long-season potato varieties that are 120 days," he said. "We don't feel we have that many good days any longer."

Climate analysts and scientists at Simon Fraser University, in nearby Burnaby, say that subtle shifts in the seasons and in weather patterns are compounding, and sometimes ending up as extreme weather events, such as the recent flooding in Calgary.

Jon O'Riordan, a former deputy minister of the B.C. Ministry of Sustainable Resource Management, has co-written a new report on climate change and Canada's crops with the SFU-based Adaptation to Climate Change think tank.

The report says higher temperatures and lack of water could lead to shortages of local or regional products such as B.C. wild salmon, Western Canadian beef, and grain; and could alter the conditions that favour the production of ice wine, maple sugar and — further afield — fruits and vegetables we import from California.

Extreme weather, more often

O'Riordan is recommending that both federal and provincial governments change their water-use laws within the next year to keep pace with the changes in weather, and to avert a food shortage crisis.

"Water and agriculture are closely entwined. In B.C., we have a Water Act that's over 100 years old and simply not adapted to the new reality we're facing in agricultural water," he said.

He wants changes to groundwater licensing and flood insurance laws, and research into new crops that will thrive in a warmer Canada.

O'Riordan says if governments don't act now, the problem will become too big to manage. Extreme weather events, such as flooding and high temperatures, are going to become more and more common, he says.

"There will be more frequent events of that nature. More intense, both on the drought side and on the flood side, and we have to start preparing for these because the frequency is going to increase over the next two decades."

Nicholas Simons, the NDP MLA for Powell River-Sunshine Coast, says the B.C. government should look at the think tank's recommendations seriously.

"We have to take action on climate change because, in the simplest terms, it impacts on our ability to survive and food production is so essential," he told CBC News.

Farmers like Zylmans welcome the spotlight on changing growing conditions. But he wonders whether the report's recommendations will be ignored, at our peril.

"You just can't take mother nature un-seriously," he said. "She can do whatever she wants to do at any time."

With files from the CBC's Meera Bains