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Wetland Loss
It is difficult to know exactly how many wetlands have been significantly altered or have disappeared from the Alberta landscape. However the loss is real in the settled parts of Alberta; the land-use changes that accompany industrial development and human settlement have altered local ecosystems where wetlands have been drained, paved over or farmed.
The Institute of Wetlands and Waterfowl Research estimates that approximately 64 per cent of the slough/marsh wetlands in the settled areas of Alberta no longer exist. “Wetlands at Work for You”, a publication of the Parks Foundation Calgary, says the city’s expansion has already consumed 80 to 90 per cent of the prairie wetlands that once comprised the area where Calgarians now live, work and play.
The Alberta picture
According to data from the Pembina Institute, wetland loss in Alberta equates to an annual economic loss of $3,650 per hectare.
In 1988 dollars, the estimated loss in cumulative area of Alberta’s wetlands was tallied at $7.7 billion or 7 per cent of Alberta’s 1999 gross domestic product (GDP). Using a GDP index that rates existing wetlands (1999) on a scale of zero to 100, the Pembina Institute ranked the status of Alberta’s wetlands at 39.6. The report also gives Alberta’s remaining wetlands a value between $5 billion and $30billion to Alberta’s economy for 1999 values.
What can we do about it?
Alberta’s wetlands have been disappearing since late 1800s and are sensitive to water and land management. These natural areas continue to be under direct and indirect pressures from human settlement that may result in further loss or degradation.
It is important to consider threats to wetlands in the context of the entire watershed. Some of the main activities that can negatively impact wetlands include:
- Dredging, draining, and/or filling wetland areas for conversion to agricultural, industrial or residential lands
- Population growth and urban development
- Sand and gravel mining and mineral extraction activities
- Peat extraction activities
- Timber harvesting
- Oil and gas exploration
- Waste disposal
- Storm-water pollution and water contamination
- Nutrient enrichment
Ignorance costs us all
Lack of understanding is one of the major threats to wetland health and longevity. Filling in or draining a single hectare of wetland can negatively impact the surrounding landscape.
The negative effects of wetland loss are cumulative. Every time a wetland is lost, or allowed to degrade, the entire watershed loses value to humans, animals and plants.
Steps to preventing wetland loss and degradation begin with the knowledge that wetland retention is better than wetland restoration. Experience shows the economic cost associated with the construction of expensive flood control works, or the dollar cost of restoring destroyed or degraded wetlands to their former biological state, can be prohibitive—and sometimes impossible to justify.
Knowing the impact on wetlands of various activities and land-use choices helps make better decisions to protect these natural areas.
The loss or destruction of wetlands can result in:
- Loss or degradation of wetland habitat and a loss of plant and animal biological diversity
- Deterioration of wetland water quality
- Reduction in water supply and water storage
- Increased occurrence of algae blooms caused by nutrient overload from land adjacent to a wetland
- Increased sedimentation, which negatively impacts natural filtration
- Loss of flood plain land and flood plain protection
- Reduced range of recreational opportunities
- Loss of aesthetic values
- Increased abundance of weeds
- Loss of species and shifts in species dominance
- Mosquito problems
- Changed hydraulic regimes, such as permanent water cover in a wetland with a natural cycle of wet and dry periods
- Reduction in groundwater recharge, with a negative impact on potential crop production and secure water supplies for humans and livestock
- Increased soil erosion
Other threats to wetlands – pesticide use
Pesticide use in Canada has been on the rise since the Second World War, with a 500 per cent increase in treated land from 1971 to 1991. Pesticides are transported into water bodies by direct over spray by:
- Aerial drift of pesticide droplets
- Wind drift of particles with absorbed pesticides,
- Dissolution in surface runoff, snowmelt or groundwater, or
- Accidental spills.
Studies of pesticide residues in wetlands across North America have reported moderate to high concentration levels. An Alberta study, conducted in 2000, reported measurable levels of pesticide residues in 55 (or 92%) of the 60 semi-permanent wetlands tested.
The economics of wetland loss
An international study of wetland economics released in January 2004 by the World Wildlife Fund (WWF) confirms these natural areas produce a number of economically-important goods and services including food, fresh water, building materials, water treatment, and flood control. Recreational opportunities, storm buffering and aesthetic amenities are other economic attributes of wetlands.
Using data from the Ramsar Convention, the WWF study estimates that wetlands contribute $70 billion a year to the world economy. The study also estimates that half of the world’s wetlands have been lost since the 1900s causing a loss of economic wealth globally.
