Land use changes can alter climate, says MCDA keynote speaker

Those who doubt that human activity can affect global climate — or for that matter, turn Lake Winnipeg into a toxic green soup — should brush up on their history.

In his keynote address at the recent Manitoba Conservation Districts Association annual conference, Bob Sandford, the EPCOR chair of the Canadian Partnership initiative in support of the United Nations’ Water for Life decade, explained the linkages between climate change, hydrology, and eutrophication.

“Civilizations that existed long before fossil fuels knew the consequences of sweeping land-use changes. They learned the hard way that if you dramatically alter the landscape through deforestation, agricultural transformation or urbanization, you alter the hydrology of a given region,” said Sandford.

“If the land is altered and its hydrology changed, the climate invariably changes too.”

Sandford cited statistics for Manitoba from 1831 to show how much humans have changed the landscape. At that time, there were just 2,152 acres under cultivation. Now, there are 18.8 million acres of farmland of which 13.5 million are in annual crops.

He also noted that over that same period, farming practices have changed from oxen-drawn stoneboats filled with scarce manure to synthetic fertilizers that arrive by the truck- and trainload.

One unintended consequence of the changing face of agriculture — both locally and globally — has been the eutrophication of fresh water supplies to the point that it has been added to the top 10 list of pressing environmental crises today.

Blue-green algae blooms aren’t just a problem for urban beachgoers and fishermen, he added. They are formed by cyanobacteria, dubbed the “cockroaches of the aquatic world” for their tenacity, which produce toxins that can kill livestock.

Cyanobacteria over the maximum guidelines have been detected in 246 water bodies across Canada, and with a warming climate and increased nutrient run-off, they are becoming more widespread and more toxic, he said.

Water management

Greg McCullough, a research scientist at the University of Manitoba, cited recent studies that indicate a need for better upstream water management, not just restricting nutrients.

His research has shown that repeated flooding leads to not only higher volumes of phosphorus in the additional water, but also much higher concentrations of the nutrient.

“It’s getting wetter, and we’re getting more floods, and that flooding is dissolving more nutrients off the land,” said McCullough.

Upstream water storage in preserved or restored wetlands could alleviate flood surges and therefore protect Lake Winnipeg from further eutrophication, he said.

Climate change is causing increased rainfall, said Sandford, which can be traced back to “weakening and meandering” in the jet stream caused by a melting Arctic ice cap that now allows subtropical storm fronts to penetrate farther north.

That means the loss of the polar ice cap, which serves as a kind of “thermal helmet” that stabilizes the global climate, would leave the planet vulnerable to “warming shots right to the head.”

“If we lose the refrigerating effect of the polar sea ice, temperatures could skyrocket,” said Sandford.

‘Atmospheric rivers’

Rising temperatures mean more severe storms, because for every degree rise in global temperatures, the water-holding capacity of the atmosphere increases by seven per cent.

Destabilized historical weather patterns could give rise to more “atmospheric rivers,” which are narrow bands of extremely concentrated water vapour spun off from ocean weather systems that penetrate deep into continental areas.

Containing many times more water than even the Amazon or Mississippi rivers, the recently discovered weather phenomenon has been linked to massively destructive storms such as the one that flooded Calgary last summer.

But while Canada’s attention was fixed on Alberta’s woes, a far more alarming situation was developing in Russia, said Sandford.

A weakening of the European jet stream created a “heat dome” over northern Siberia that led to hundreds of wildfires in July that were so hot they melted the permafrost, which released methane to further fuel the firestorm.

Then in August, three atmospheric rivers collided over the region and flooded one million square kilometres in just four days.

“It was the stuff of science fiction. Fires and floods of a magnitude seldom experienced before on the same river basin in the same year,” said Sandford.

Such phenomenon are likely to continue as a “new normal,” he added, noting that the Mauna Loa Observatory this summer recorded atmospheric CO2 levels in excess of 400 parts per million, up from 320 ppm in the 1960s.

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