Escalating tensions between water users are among the key challenges facing North America says the Intergovernmental Panel on Climate Change (IPCC). Many water resources across the region are already heavily utilized by industry, agriculture, for drinking water and hydropower.
Shifts in rainfall patterns, melting mountain glaciers, rising temperatures, increased demand and reduced supplies in some places are likely to aggravate the situation unless cuts are made in greenhouse gases to reduce the scale and pace of climate change.
Ground-water flows from the Edwards Aquifer in Texas for example could drop by up to 40 per cent leading to economic losses for farmers. Summer flows in some river systems such as the Colorado and Columbia basin are likely to decline sharply within four decades. This is expected to increase competition between industry, cities, hydropower operators, farmers and fishermen for freshwater supplies.
Other climate-related impacts include increased growth of Lodge pole pine-- a widespread species in North America-- in its northern range, decreased growth in its middle range and devastation of its southern forests under a three degree C temperature rise.
North American producers of wood and timber could suffer losses of between $1 billion and $2 billion a year during the 21st century if climate change also sparks changes in diseases, insect attacks and forest fires. Between 15 per cent and close to 40 per cent of plant and animal species will be “committed to extinction” by 2050.
Over the coming decades, up to a fifth of the remaining coastal wetlands in the mid-Atlantic region of the United States like those in Chesapeake Bay will be at risk of inundation as a result of impacts such as sea level rise and storm surges.
Cities could also be at risk from high tides and storm surges. Towards the end of the century-- under a strong warming scenario--a current one in 100 year flood in New York could have a return period of three to four years.
A 25 per cent increase in heat waves is projected for Chicago later this century with the estimated increase in Los Angeles rising from the current 12 days to between 44 and close to a 100.
The report notes that while North America has “considerable adaptive capacity, actual practices have not always protected people and property from adverse impacts of climate variability and extreme weather events”.
Some of the challenges facing North America in terms of adaptation include a lack of information on climate change and its likely local impacts, financial barriers and the slow turnover of existing infrastructure. The report cites the case of Hurricane Andrew in the early 1990s and the development of property building codes. “If all properties in southern California met this updated code, the property damage would have been lower by nearly 45 per cent”.
“Some early steps toward planned adaptation have been taken by the engineering community, insurance companies, water managers, public health officials, forest managers and hydroelectric producers,” says the report but adds that there is a great deal still to be done.
“Mainstreaming climate change issues into decision making is a key prerequisite for sustainability,” it says.
Achim Steiner, Executive Director of the UN Environment Programme (UNEP) which co-founded the IPCC, said: “Canada and the United States are, despite being strong economies with the financial power to cope, facing many of the same impacts that are projected for the rest of the world”.
“Moreover in some areas, such as already heavily utilized water resources, the impacts could be acute and may require very careful, strategic planning and investment if tensions are to be avoided between humans and nature and between a wide-range of economically and socially important water users,” he said.
“Overall the findings underline that the best and probably most cost effective form of adaptation is mitigation—in other words deep and decisive cuts in greenhouse gas emissions to avoid dangerous climate change in the first place,” said Mr Steiner.
“Heavily-utilized water systems of the western US and Canada, such as the Columbia River, that rely on capturing snowmelt runoff will be especially vulnerable,” says the Fourth report of IPCC Working Group II.
A two degree C warming by the 2040s is likely to lead to sharply reduced summer flows coinciding with sharply rising demand. The report estimates that Portland, Oregon will by then require over 26 million additional cubic meters of water as a result of climate change and population growth. This will coincide with a fall in summer supplies from the Columbia River by an estimated five million cubic meters.
Meanwhile, just over 40 per cent of the supply to southern California is likely to be vulnerable by the 2020s due to warming triggering losses of the Sierra Nevada and Colorado River basin snow pack. "Lower levels in the Great Lakes are likely to influence many sectors. Adapting infrastructure and dredging would entail a range of costs,” says the report.
This is likely to exacerbate controversies linked with water diversions to cities such as Chicago and the competing demands of water quality, lake-based transport and drought mitigation. Summer temperatures in Midwestern and southern lakes and reservoirs could exceed 30 degrees C.
Levels of phosphorus, a nutrient from sources like sewage and detergents which can trigger algal blooms and oxygen scarce waters, are likely to rise in some bays in the Great Lakes by as much as 98 per cent.
Heavily-utilized ground waters are likely to come under increasing stress as a result of climate change. “Simulations of the Edwards aquifer in Texas project lower or ceased flows from springs, water shortages and considerable negative environmental impacts,” says the report.
Economic losses, for example to agriculture could amount to just over $2 million to nearly $7 million a year as water allocation is shifted to industry and cities. Other vulnerable supplies include Ogalla Aquifer—a shallow formation which underlies South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico and Texas. Here a 2.5 degree C temperature rise or more reduces natural re-charge of the aquifer by over a fifth.
Cities and Towns
Some northern settlements are at “moderate to high hazard” by the middle of the 21st century as a result of coastal erosion and the thawing of permafrost, says the report.
These include Shishmaref, Nome and Barrow in Alaska and Tuktoyaktuk in the Northwestern Territories. Infrastructure at risk includes the Dalton Highway in Alaska, the Dempster Highway in Yukon, airfields in the Hudson Bay region and the Alaska railroad.
By the 2090s, a one in 500 year flood in New York could be a one in 50 year event “putting much of the region’s infrastructure at risk”. Boston’s urban transportation network may also be at risk from a sea level rise of 3 mm a year and an increased probability of a 100 year storm surge.
Tourism and Recreation
Nature-based tourism is a major market sector with over 900 million visitor-days in national, provincial and state parks in 2001. Canada’s national parks may see an increase of up to 40 per cent by the 2080s as a result of a longer warm weather season.
However, this might be offset by other climate change-induced factors such as loss of glaciers, changes in biodiversity and fire and pest-related impacts on forests.
The costs of replenishing Florida’s beaches with sand, in order to counter a sea level rise of half a metre, could be between nearly $2 billion and close to $9 billion.
The North American snowmobiling industry, currently worth $27 billion, may be hardest hit because it relies on natural snowfall rather than artificially-made snow. A reliable snowmobile season disappears from most regions of eastern North America by the 2050s.
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