Humans now dominate most ecosystems on Earth. In Canada, with more wilderness than most countries, the domination is not always obvious – but even in remote areas human influence is increasingly apparent. In this section we look at status and trends of some of the actions Canadians are taking to conserve ecosystems, some stressors on ecosystems that are by–products of human activity, and trends in goods and services provided by healthy and diverse ecosystems.
As of May 2009, 9.4% of Canada’s land area and 0.64% of its ocean area had provincial, territorial, or federal protected–area designation. Large and small protected areas have a role to play in biodiversity conservation. Thirty–six protected areas in Canada are larger than 5,000 km2, making up 59% of the total area protected. In several places, adjacent protected areas create large protected–area complexes. At the other end of the scale, 3,464 protected areas smaller than 10 km2, which make up less than 1% of the total area protected, play an important role in protecting rare species and habitats. Progress has been made in identifying potential sites for marine protected areas, although designation of marine areas has been slow.
Over a million people and a thousand stewardship groups participate in stewardship activities in Canada – everything from community projects to government initiatives. Tax incentives, conservation easements, and the growth of land trusts have helped facilitate stewardship on private land. Also important are large, landscape–level initiatives. For example, the North American Waterfowl Management Plan has influenced the stewardship of over 70,000 km2 of wetland, grassland, and agricultural habitat across Canada in the 2000s alone. Standards and codes of practice, such as forest and marine certification, are important tools in the stewardship of public and private lands and waters. Participation in all forms of stewardship has increased substantially since the 1980s.
Invasive non–native species are considered the second greatest threat to biodiversity world–wide, after habitat destruction. Ecosystems that are already altered or degraded are more vulnerable to colonization by aggressive non–native species. Non–native species are destroying valuable wetland and grassland habitat, are invading marine intertidal areas, and dominate the Great Lakes. Economic and ecological losses caused by invasive non–native species have been estimated at $5.7 billion annually in the Great Lakes alone. Wildlife diseases caused by non–native pathogens, such as West Nile virus, have killed thousands of birds and potentially threaten many different wildlife species.
Levels of legacy contaminants – banned or restricted chemicals, such as PCBs – have declined in wildlife in the Strait of Georgia, St Lawrence Estuary, Great Lakes, Bay of Fundy, and the Arctic since the 1970s, although rates of decline in some areas have slowed in recent years. The recovery of peregrine falcons after the banning of DDT demonstrates that some species can rebound after the contaminant stress has been lifted. Flame retardants (PBDEs) are examples of emerging contaminants, which have more recently been found to spread through and accumulate in ecosystems. PBDE levels have increased since the 1980s in fish, birds, whales, and polar bears. Contaminants can directly affect wildlife health and reproduction and increase vulnerability to other stressors.
Fertilizers from agriculture, phosphates from detergents and industry, and sewage from towns and cities add nutrients to aquatic systems, sometimes causing algal blooms. In recent years, algal blooms have been reported in lakes, reservoirs, ponds, rivers, swamps, and estuaries across the southern half of the country. Some past successes in nutrient reductions, particularly in the Great Lakes, are now being reversed. Over the past 16 years, nitrogen has increased in 28% of water bodies sampled and decreased in 12%, while phosphorus has increased in 21% and decreased in 29%. Although harmful marine algal blooms occur naturally, they appear to be increasing in the oceans off Canada’s coasts.
Acid deposition occurs when sulphur and nitrogen–based air pollutants react with water and settle on the Earth's surface. In aquatic systems, the survival of many species is threatened by the acidification of their habitat. Emissions have declined since 1980, but improvements in lake acidity have been slow to follow. Some areas, such as parts of the Boreal Shield, have acid deposition levels beyond the ability of the ecosystem to cope. The Atlantic Maritime has some of the most acidic waters and heavily affected fish habitat in North America. Although acidification is often considered an eastern issue, it is an increasing concern in parts of the West. In northwest Saskatchewan, for example, many lakes downwind of oil and gas development emissions are sensitive to acid deposition.
Canada’s climate has changed significantly since the 1950s. Temperatures have increased across the country, especially in winter and spring. Spring now arrives earlier, meaning snow melts earlier and growing seasons are longer. Precipitation has generally increased, especially in the North. The average annual temperature has increased by 1.4°C. No significant cooling trend has occurred at any location in any season. Changes in climate have led to widespread environmental changes, such as loss of sea ice. Some currently localized changes are likely to increase and become more widespread with continued warming. These include rising sea levels, higher seawater temperatures, and increases in wildfires. Ecosystems and species are affected by all of these changes, often in complex and unexpected ways that interact with other stressors, such as habitat fragmentation
Many of Canada’s vast wetlands, coastal ecosystems, and forests are healthy and provide billions of dollars in ecosystem services annually. Services include commercial, recreational, and subsistence food gathering, flood and drought control, sediment filtering, nutrient cycling, erosion control, and climate regulation. There are also signs of loss of ecosystem services. Increased erosion, spread of wildlife diseases, and less predictable river flows have been documented. Several commercial fisheries are declining. Subsistence opportunities are hampered by wildlife population declines, contaminants in culturally important species, and, in the North, by altered access to harvesting due to changes in ice and permafrost. Recreational opportunities are affected by closed beaches, fouled fishing equipment, and invasive non–native species.