Coastal

Status and Trends
most less developed coasts: healthy but under pressure
Healthy, getting worse at a slow to moderate rate
good data for some regions only; trends clear where data exist
Impaired, getting worse at a slow to moderate rate
good data for some regions only
Medium confidence in finding

KEY FINDING 5. Coastal ecosystems, such as estuaries, salt marshes, and mud flats, are believed to be healthy in less-developed coastal areas, although there are exceptions. In developed areas, extent and quality of coastal ecosystems are declining as a result of habitat modification, erosion, and sea-level rise.

This key finding is divided into five sections:

Coastal ecosystems occur at the interface between land and sea. They include intertidal zones, estuaries, salt marshes, mud flats, seagrass meadows, beaches, cliffs, banks, and dunes. Bounded by three oceans, Canada has the longest marine coastline in the world, with 29% of the world's total coastline.1 Coastal ecosystems are important as they are particularly productive environments. Canadian coastal ecosystems support a diversity of marine and terrestrial species, including members of all major groups of marine organisms, approximately 1,100 species of fish, and numerous marine mammals, birds, plants, and invertebrates.2

Developed coastlines In Canada, as elsewhere in the world, increasing human population and development of coastal regions is resulting in ongoing loss and degradation of coastal ecosystems. Infrastructure, industry, commercial activity, and settlements near the coast have depleted and altered natural systems and made coastlines more sensitive to erosion. Wetlands, including salt marshes and estuarine habitat, were severely depleted during early development of the populated areas of Canada's east and west coasts. Further losses will occur as sea levels rise, especially where development now leaves only a narrow margin of habitat. Inventories are available of extent and sensitivity of some coastal ecosystems,3-5 but information on past and current rates of loss and alteration is sparse.

Less developed coastlines Sea-level rise and changes in sea ice are examples of emerging stressors that are altering ecosystems in coastal areas that are not greatly affected by development. For example, along the southwestern, western, and eastern coasts of Newfoundland, the combination of rising sea level and changing offshore winter ice conditions, along with increased human use of the coast for residences and tourism, has resulted in widespread acceleration of erosion and degradation of dunes and coastline.6-9 In Quebec, from the upper estuary to the Gulf of St. Lawrence, rates of coastal erosion measured from 1990 to 2004 were higher than those measured before 1990. This was likely influenced Photo: protected coastal wetlands at Lord Selkirk Provincial Park, P.E.I. © iStock.com/Photawaby changes in climate-related processes such as ice scouring and wave action.10 Erosion in sensitive areas of the Beaufort Sea coastline may also increase because of reduction in sea ice, melting ground ice, and increase in storms11 as is currently happening along the coast of the Alaskan Beaufort Sea.12

It is estimated that up to 65% of Atlantic coastal marshes have been lost since the 1700s as a result of dyking and drainage for agriculture and settlement, and more recently for industrial and recreational development as well.15, 16

Globe

Global Trends

An estimated 19% of land within 100 km of the coast (excluding Antarctica) has been converted for agriculture and urbanization. Important coastal habitats, including mangroves, wetlands, seagrasses, and coral reefs, are disappearing rapidly.13, 14

Return to Table of Contents

Photo: low tide © iStock.com/liquidfog
Low tide, New Brunswick

Atlantic coastal ecosystems

Increase in development along Atlantic coasts

Number of lot registrations (thousands), within 2 km of the Nova Scotia coastline
Graph: increase in development along Atlantic coasts. Click for graphic description (new window).
Source: adapted from CBCL Limited, 20093, data from N.S. Property Online Database

Coastal development, including converting natural ecosystems to built-up areas, often increases sensitivity to erosion, impairs
coastal water quality, and alters wildlife habitat. In Nova Scotia, although increased urbanization has led to population declines
in many rural areas, human population along the coast has increased.3 In the more densely populated areas of Newfoundland, where human activity has been modifying the shoreline for more than 100 years,22 many types of activities contribute to increasing rates of erosion.9 For example, compaction of beach sediment by all-terrain vehicles leads to incoming waves washing further landward, increasing erosion above the mean high-tide line.23

Decline in wetlands and beach and dune habitat, Atlantic coast

Percent change, 1944 to 2001
Graph and map displaying decline in wetlands and beach and dune habitat. Click for graphic description (new window).
Source: adapted from O'Carroll et al., 200617 and Hanson et al., 200618

Coastal wetlands and beach and dune habitats declined at five sites in southeastern New Brunswick between 1944 and 2001. Total losses at each site ranged from 7 to 18 ha for beaches and dunes, and from 30 to 55 ha for wetlands. Erosion, removal of sand for aggregate production, and increased hardening of the foreshore for development have contributed to these losses. Beaches and dunes provide important habitat for species such as the endangered Atlantic population of piping plovers, which decreased by 17% from 1991 to 2006, partly due to habitat loss and degradation from accelerating coastal development.19-21

Sea-level rise, storms, and coastal erosion

Increase in water level in Charlottetown Harbour
Metres above reference level on land, 1911 to 2008
Graph:  increase in water level in Charlottetown Harbour. Click for graphic description (new window).
Source: adapted from Marine Environmental Data Service, 2008 in CBCL Limited, 20093

Sea-level rise and associated storm impacts are likely to increase erosion along the Atlantic coast.3, 17, 24, 25 Water level relative to land in six Atlantic harbours is currently rising at rates from 22 to 32 cm per century, over half of which is due to land subsidence.3 (The land in this region is still affected by changing ice and water loads following glacier retreat.) The remainder of the increase, about 12 cm per century at Charlottetown, is a signal of global and regional sea-level rise. This rate is anticipated to increase due to climate change.4, 26 Canada's Atlantic coast is particularly sensitive to ecological damage from sea-level rise because there are many low-lying areas with salt marshes, barrier beaches, and lagoons.27 Impacts from sea-level rise are compounded by the effects of storm surges, which are increasing in number and intensity because of increases in tropical storms.9, 28-31

Return to Table of Contents

Pacific intertidal wetlands

Loss of intertidal wetlands in southern British Columbia

Loss of intertidal wetlands to urban, agricultural, and industrial development was greatest at the turn of the 20th century, but continues today due to the pressures of human population growth.38, 39 About 76% of B.C.'s population lives in coastal communities, mainly in the Lower Mainland and southeastern Vancouver Island.40 The population of coastal B.C. is projected to increase by almost one million people by 2025.5

Total loss of intertidal wetlands, mainly through dyking for agriculture in the early part of the 20th century, is estimated at 70% for the Fraser River estuary and 32% for major estuaries along the east coast of Vancouver Island.39

Photo: western Sandpipers, Boundary Bay © John Hayes
 
Boundary Bay is part of the Fraser River estuary. The extensive (5,000 ha)42 mud flats support the largest known migrant populations of western sandpipers and the largest Canadian winter populations of dunlins, black-bellied plovers, and great blue herons.43
 

There are over 440 estuaries in the Pacific Maritime Ecozone+, most with fairly small intertidal zones of 1 to 10 ha.41 The largest estuary is that of the Fraser River, with about 21,000 ha of intertidal wetlands remaining. Although estuaries occupy less than 3% of the coast,41 an estimated 80% of coastal wildlife, including birds, fish, mammals, and invertebrates, use estuarine habitat at some point in their life cycle.5 Estuaries are also important to surrounding land and water ecosystems because of their role in water filtration and nutrient cycling.41

Return to Table of Contents

Hudson Plains salt marshes

The salt marshes of the Hudson Plains are an exception to the general finding that coastal habitats in less-developed areas are healthy. These coastal marshes are under stress from the increasing population of mid-continent lesser snow geese. The goose population increase is mainly due to human influences outside of the region, including increased supply of agricultural food on wintering grounds in the United States and along migration routes, along with declining harvest and the development of refuges.33, 34

Loss of salt marsh vegetation from snow goose foraging, Hudson Plains

Areas with vegetation loss, La Perouse Bay, Manitoba
Map: loss of salt marsh vegetation in La Perouse Bay. Click for graphic description (new window).
Source: adapted from Jefferies et al., 200632

Intensive foraging by snow geese has led to vegetation loss, shifts in plant community composition, and exposure and sometimes erosion of sediment.32, 34, 35 This results in large areas of exposed sediment that are resistant to re-colonization because few plants can germinate or establish themselves in the saline sediments. Approximately one third of the coastal salt marsh vegetation in the Hudson Plains Ecozone+ has been destroyed by geese and a far greater area will be severely damaged if this intense foraging pressure continues.36

Mid-continent lesser snow goose population
Millions, 1970 to 2008
Graph: mid-continent lesser snow goose population. Click for graphic description (new window). Photo: Snow goose © iStock.com/stasvolik.
Source: adapted from Canadian Wildlife Service Waterfowl Committee, 200937

Return to Table of Contents

Photo: eelgrass © Gabriolan.ca
Eelgrass

Eelgrass meadows: a coastal ecosystem at risk

Eelgrass meadows are among the most productive ecosystems in the world,44 and among the most threatened.45 They are declining globally, with mixed and often uncertain status along Canadian coasts. Seagrass meadows, which include eelgrass, have declined at an average rate of 7% per year around the world since 1990, an acceleration from an annual decline of less than 1% prior to 1940.46 Declines are most often associated with stressors, such as eutrophication and increased turbidity of coastal waters, mainly related to the growth of coastal human populations. The global analysis on which these rates of decline are based45 does not include Canada due to lack of adequate trend data.

Major regional declines have occurred in the past. In the early 1930s, thousands of hectares of eelgrass disappeared in eastern North America,46 attributed to eelgrass wasting disease, although climatic conditions may also have played a role.47

Eelgrass, a flowering marine plant that forms extensive subtidal beds in sand and mud along coastlines, traps particulate matter and plankton and provides habitat for invertebrates, fish, and marine mammals. Eelgrass is an important food for migrating and wintering waterfowl, and provides foraging areas for other birds.48-50

Pacific On the Pacific coast, where eelgrass beds are spawning grounds for herring and rearing habitat for salmon, some declines may be due to the Pacific oyster, which was introduced for oyster farming and has spread into the wild. Oysters alter habitat physically and may also cause sulphide to accumulate in sediments – the net result is that eelgrass is typically absent seaward of oyster beds.51, 52 Other declines are related to development of coastal areas, for example for log storage and harbours.41 A nonnative dwarf species of eelgrass that thrives higher up in the intertidal zone than does native eelgrass has taken hold in some areas of southern B.C., with mixed ecological consequences. Colonization of mudflats by dwarf eelgrass meadows on Roberts Bank in the Fraser river estuary53-55 has displaced migratory shorebirds that graze on the thin film of organic matter covering the mud.55

James Bay Eelgrass beds along the east coast of James Bay were among the most extensive in North America, covering 250 km2 prior to their rapid decline around 1998.56 Since the decline, eelgrass has shown signs of recovery,57 but neither the cause of the decline nor the present status are well understood.48 Alternative explanations for the decline in James Bay have been put forward, such as:

  • an outbreak of eelgrass wasting disease triggered by a year with unusually high summer and winter temperatures, along with changes to habitat from coastal uplift and climate change;57
  • impaired growth and survival due to reduced salinity of water in James Bay resulting from larger and more frequent discharges of fresh water via the La Grande River, due to diversions.50
Decline of eelgrass in James Bay
Dry leaf biomass (g/m2)
Graph: eelgrass decline in James Bay. Click for graphic description (new window).
Note: samples were taken at several depths at six
sites – this figure shows results typical at all depths
for five of the six sites. The sixth site showed no
change. No data for 1992 and 1996-1997.
Source: adapted from Hydro-Quebec and
GENIVAR Group Conseil Inc., 200557

Atlantic Coast and Gulf of St. Lawrence Compiling results from a number of mainly short-term studies provides a picture of a general decline in eelgrass and some abrupt die-offs, along with some areas with stable to increasing trends.44, 49 One factor in declines on the Atlantic coast is the spread of the invasive green crab, which can uproot eelgrass plants.53 Some study results:

LocationYearsEelgrass trends
Lobster Bay, N.S.1978 to 2000estimated losses of 30% and 44% in two areas58
4 Nova Scotia inlets1992 to 2002loss of 80% of total intertidal area occupied by eelgrass59
13 southern Gulf of St. Lawrence estuaries2001 to 2002biomass decline of 40%60
Antigonish Harbour, N.S.2000 to 2001biomass decline of 95% followed by 50% decline in geese and ducks that feed on the eelgrass61
Newfoundlandpast decadeincrease in abundance, based on local knowledge, possibly due to milder temperatures and changes in sea ice44
Gulf of St. Lawrence in QuebecvariousManicouagan Peninsula distribution expanded (1986 to 2004); generally also expanding or stable in other areas62

Return to Table of Contents