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DELTA MARSH

Resource Management

Presentation


www.wilds.mb.ca/delta

Updated December 25, 2000

Information herein is from a presentation given
by Dr. Jennifer Shay
to the Manitoba Naturalists Society on February 9, 1998.


 

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Wise Resource Management

by Dr. Jennifer Shay

Can we make wise resource management decisions?

In addressing this topic, "Can we make wise resource management decisions?", I want to briefly consider what we mean by resource management, and then discuss two important but contrasting ecosystems in Manitoba - one a wetland, the other a prairie. Both provide economic benefits for people, both are home to a wide array of plants and animals, both have been subject to management and both provide lessons for us if we are willing to listen, to learn and to respond.

Resource management amounts to intervention within the ecosystem, either to alter the status quo in a wanted direction, or to prevent the status quo from being altered in an unwanted direction.

Resource management usually involves conflict and uncertainty. Conflict because there are often a wide range of conflicting interests - farmers, hunters, environmentalists, governments and others - each clamoring to be satisfied. Successful management decisions involve a balanced approach in which these conflicting interests must each compromise. Such trade-offs are essential for success in the long-term.

Resource management usually involves uncertainty because managers are almost always faced with a lack of specific data about biological populations and processes, and therefore must rely upon estimates. Financial resources are usually scarce and thus, priorities must be established.

Once management plans are activated, records of successes and failures should be kept so that they can be evaluated and adjustments made to achieve the most appropriate management. When incorrect decisions are made, they should be publicly acknowledged.

Three broad groupings of knowledge relating to natural resources have emerged:
(1) ecological
(2) social and cultural
(3) economic

Recognition of this mix has drawn attention to the fact that in resource management and development, attention must be given to trade-offs, ie. different weights can be given to environmental, social and economic considerations. But ultimately a balanced approach is essential, with sustainability and compromise emphasized, in order to accommodate different but legitimate perspectives over the long term.

What do we mean by wise resource decisions? It depends on your perspective. For many business enterprises and many multinational corporations who use natural resources, profit is the main objective. Seldom is there any concern for the sustainability of the natural resources upon which they depend. To them, wise use is measured by profit margins and they ignore any impact on the environment.

The goal that Ottawa pursues on our behalf is for a just and prosperous Canada, and the main route to achieving this is expanded competitive commerce. The expansion of foreign markets that encourage trade helps Canada. It must be true because economists and politicians keep telling us so.

The questionable part concerns benefits in the long term. No one can doubt the short term gain. But was the exploitation of buffalo, of passenger pigeons, of the white pine wise use?

As Stan Rowe asked in one of his essays, would we starve in Canada if we'd no one with whom to trade? If we ever adopt the national goal of long term sustainability, rather than cheapness, international trade would change radically. Should Ottawa elevate above wealth and prosperity the idea of keeping our rivers clean, our forest productivity stable, our soils, lakes, marine resources in good condition? We cannot keep on taking without replacing - as witness, the depletion of the nation's forests, fisheries and agricultural soils.

I suggest that wise use of our natural resources necessitates a move away from the focus upon exploitation and single resource use, to a more balanced approach. One that carefully assesses the impact of the use on the whole ecosystem - one that strives for long term sustainability. With this in mind I'd like to consider two examples, the first is the Delta Marsh.

After reading about Delta Marsh and CFB Shilo Prairie initiatives, read the summary at the end of this page regarding the lack of political will to rejuvenate Delta Marsh.

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Delta Marsh Ecology

by Dr. Jennifer Shay

The Delta Marsh is at the south end of Lake Manitoba, 90 km north-west of Winnipeg. It is one of the largest and traditionally most important marshes in the prairies. It consists of shallow bays of water interconnected by winding channels. It covers more than 15,000 ha, but it's size varies somewhat depending on water levels.

Formation of the marsh began about 4,500 years ago. At that time the Assiniboine River flowed into the south-western end of Lake Manitoba, creating a sandy delta. As the delta expanded in the lake, currents in an easterly direction re-distributed some of the sand. Through a process called long-shore drift this created a barrier beach. By 2,500 years ago the barrier beach had cut off the wetland, now known as the Delta Marsh. Though no longer accumulating sediment from the south, the sand deposits in the lake are still being moved in an easterly direction.

The marsh lies in an area of low relief. It is only 4.4 m from the bottom of the deepest bay to the highest point on the ridge. The water depth throughout much of the marsh is only 1 m, and on an annual basis evapotranspiration exceeds precipitation, resulting in an annual growing season deficit of almost 30 cm (1 foot).

Delta Marsh Plant Succession
(relative to water depth)

Delta Marsh plant succession chart relative to water depth

The nutrient-rich, shallow water supports a luxuriant growth of algae and submerged aquatic plants, as well as bulrushes (e.g. hardstem bulrush) which border the open water and also form small islands. Common throughout the marsh is the cattail and on slightly higher ground the giant reed forms dense stands. Whitetop grass and sedges characterize the wet meadows that usually dry out at some point during the growing season. Better drained, more upland sites are colonized by sand bar willow, Manitoba maples, green ash and cotton wood. Invariably, as water depth decreases there is a change in species from pondweeds to emergent macrophytes such as bulrushes, cattails and reeds, then wet meadow species such as sedges and whitetop grass, followed by willow and other upland species.

The productivity of marsh species is substantial, it can be more than 1,000 g/m2 annually. The accumulation of so much organic material on the bottom would lead one to expect that the marsh would rapidly fill in but this has not happened [we know that marsh type vegetation has been present at Delta for more than 2,000 years].

During his M.Sc. research Albert Sproule analyzed two sediment cores taken from the bottom of Cadham Bay. He identified a range of different organisms - bryozoa and invertebrates such as molluscs, cladocera and ostracods, and seeds and pollen. One core was 220 cm long, the other 385 cm long. The sediments are silty clays and silty sands in both cores, and both cores produced similar pollen diagrams. The bottom of one core had a radiocarbon data of 2,400 and 230 years.

The pollen assemblages indicate that marsh conditions have existed since sediment deposition began about 2,000 years ago - this date coincides with the completion of the barrier beach we saw earlier. Submerged aquatics, cattails, sedges and damp ground annuals are represented throughout the cores and the species present resemble those found in the marsh today. The pollen diagrams show dramatic fluctuations in the amount of pollen, suggesting cycles in water levels. Obviously water levels changed often enough to prevent in-filling of the shallow marsh.

Lake Manitoba Levels 1920-1997
Lake Manitoba Level Chart 1920-1997

We might well ask, why have wetland conditions persisted for 2,000 years? The marsh has survived because of connections between it and Lake Manitoba which have allowed marsh water levels to fluctuate with lake levels. Periodic inundations have alternated with periods of low water. For example, since 1924 there have been four periods of 3 to 15 years duration when water levels in Lake Manitoba were higher than the long term average (view Lake Manitoba Level Chart, above). These have alternated with conditions as in the drought of the 1930's and 1940's. The high water in the 1950's resulted in the death of more than 20% of the reeds and cattails in the marsh. When the water levels fell, seeds buried in the mud that had lain dormant for years were able to germinate and the mudflats were colonized by damp ground annuals soon to be replaced by whitetop grass or cattails and a rejuvenated marsh came into being. It is this type of dieback and recolonization that has allowed the marsh to survive.

At the turn of the century when access was provided by a railroad built by the Portage Northwestern Company, Delta (the fourth station on the line) became internationally renowned as a fine waterfowl marsh with high recreational appeal. It produced ducks, geese, muskrat, mink, deer and other wildlife. Pickerel, jackfish and tulabee moved from the lake to the marsh to spawn and a fishery was established. In 1929 a road was built and the marsh soon became a mecca for bird watchers, naturalists and photographers. It is now host to the Delta Waterfowl and Wetlands Research Station (1938) and to the University of Manitoba Field Station (1965).

But for most of the century there have been conflicts between it's users - hunters, wildlife biologists, agricultural interests, Fishermen, trappers and others. Hunters want more ducks, farmers want more hayland and less duck depredation on their crops grown near the marsh, fishermen want channels open to allow access for spawning fish, trappers want adequate water depths for muskrat survival in winter and so on.

Over the years various solutions to the problems have been suggested and some implemented. In order to avoid the low water levels of the 1930's and 1940's a dam was built at the Clandeboye channel in 1944 at elevation 247.8 m. This allowed water to enter the marsh when lake levels exceeded 247.8 m but water could not drain out when lake levels fell. Several other connections between the lake and marsh were blocked.

High water levels in Lake Manitoba in the mid-1950's overtopped the Clandeboye dam, killed marsh vegetation, and rejuvenated the marsh but it flooded marginal haylands. Agricultural lobbying resulted in the construction of a dam at Fairford to regulate Lake Manitoba with a target of 247.5 m (reducing it's fluctuations from 2 m to 60 cm).

PROBLEM

PERCEIVED SOLUTION

1930's and 1940's
low water levels reduced marsh productivity

1944 Clandeboye dam built at 247.8 m elevation

1954-1957
high water flooded marginal farmland and killed marsh vegetation

1961 Fairford dam built to regulate Lake Manitoba with target of 247.5 m

Because of the importance of the marsh, the Canadian Wildlife Service carried out an intensive study between 1964 and 1967. They collected data on the physical and biological characteristics of the area. Weekly waterfowl surveys were conducted over the entire marsh. Water levels were recorded, vegetation types mapped from color aerial photographs. Muskrat house counts were made, land values were obtained, underwater contours were mapped and an engineering feasibility study outlined the development possibilities and the associated costs. During the study screens were erected on the channels linking the lake and marsh to keep out carp, an introduced fish. At these locations a substantial carp fishery thrived.

This study recommended:

Appointment of a marsh manager

Construction of 1 or 2 compartments in the marsh to permit water manipulation

Maintain the carp barriers

Study fishery potential

Purchase marginal haylands to 244.8 m to reduce conflicts between agriculture and wildlife.

They also put a price tag of about $1,011,200.00 CDN on the marsh value at that time. In 1998 dollars (Approximately × 10) $10,112,000.00 CDN.

The next intervention was in response to flooding in the Assiniboine River valley; the Portage diversion was constructed in 1968, to divert flows from the Assiniboine River. A reservoir was constructed at Portage la Prairie to allow sediments to settle out. Nevertheless, when the Diversion is in operation a huge sediment load is carried down to Lake Manitoba and when the Diversion's capacity is exceeded and the "tail safe" in the west dyke is used, sediments extend far into the west marsh. The marsh has been flooded four times since 1974.


  Aerial Images of Crescent Pond at Delta Marsh
Delta Marsh Aerial Photos 1974, 1987, 1997

Over the years two plans to construct compartments in the marsh have been proposed, one in the 1960's, the other in the 1980's when extensive dyking and the installation of control structures were proposed by D.U. but the price tag was high, $15 million, and there was considerable opposition from farmers and others so the plan did not come to fruition.

We know from the calculations of Gordon Goldsborough and others that specific sites in the marsh such as Crescent pond will be completely filled by cattails within the next 25 years if the present trends continue.



We know that:

To remain viable marshes need high water levels of long enough duration to kill emergent vegetation and drawdowns to allow revegetation.

Carp are deleterious to pondweeds and other aquatic plants and this affects fall waterfowl populations, particularly diving ducks.

Other fish species have declined dramatically.

Infilling of small ponds and sloughs has accelerated.

Lake Manitoba shoreline configuration has changed under the stable lake levels.

Construction of the Portage diversion blocked Cram Creek and caused flooding problems on it's east side resulting in expenditures of millions of dollars in compensation to farmers.

There has been an increase in the use of fertilizers and other chemicals on adjacent farmlands and hence into the marsh.

Hundreds of thousands of dollars have been spent on water control works and studies.

Was it a mistake to stick rigidly to the regulation of Lake Manitoba at 247.5 m and eliminate the highs and lows in the lake?

Was it a mistake to block Cram Creek when the Diversion was constructed?

Should carp screens have been maintained?

The answer to these questions depends on one's point of view. But we have in place all the ingredients to return one of the continents most famous marshes to a naturally productive and dynamic ecosystem. Since the mid 1960's I have suggested that serious consideration be given to periodic deregulation of Lake Manitoba with compensation for those negatively affected. Deregulation could involve lowering Lake Manitoba to allow revegetation of exposed mudflats of all the marshes in the Lake Manitoba basin or it could involve raising water levels to kill off the cattails that have invaded shallow water. Dr. Bruce Batt, a former director of the Delta Waterfowl and Wetlands Research Station states in a soon to be published book that "de-regulation of Lake Manitoba would be the cheapest solution, but this is unlikely to occur because of opposition by cottage owners, farmers and other single use interests".

If the expenditures for management decisions that have occurred were calculated and the associated compensation to injured parties and the cost of studies and management plans that have been drawn up over the years added, the dollars expended would be in the millions. Clearly the management interventions to date have not resulted in a viable marsh, but we know the marsh has existed for more than 2,000 years. We have the knowledge, but we lack the leadership and will to do the right thing. If we take no action will we be seeing the sunset over the Delta Marsh in the next few decades?

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Shilo Prairie Ecology

by Dr. Jennifer Shay

The second landscape that I'd like to discuss is mixed grass prairie at the Canadian Forces Base at Shilo, Manitoba. CFB Shilo is close to Carberry about 190 km west of Winnipeg.

It is part of the upper Assiniboine Delta where the ancient Assiniboine River once flowed into Glacial Lake Agassiz. The coarse textured sands support the largest extent of mixed grass prairie in the province. Some of the characteristic plants are prairie crocus, field chickweed, puccoon, bergamot, gramma grass, prairie sage, echinacea and brown-eyed susan.

In 1924, the Department of National Defense leased 48 sq. miles (12,400 ha) from the Province of Manitoba. Since that time parts of the area have been used for Canadian army training activities. By the 1970's the Manitoba Naturalists Society and others expressed concern about the impact of frequent fires and training activities on the environment, with the result that in 1972 a Shilo Environmental Advisory Committee (SEAC) was formed. This committee has representatives from the army, the federal and provincial government, the Manitoba Museum and the University of Manitoba. When the lease with the army was renewed in 1973 it included an order-in-council that stated that the army should restore the Crown land to the condition existing before it's occupancy. In 1974, use of the area increased when an agreement was forged with the German army. Since then every 21 days from May until October as many as 700 German troops a year visit the base for mechanized training - ie. there are 8 rotations of troops to the base. The local economy has benefited from the infusion of $50 million a year.

With the increased activity SEAC became concerned with the deterioration of the prairie. They were concerned about weed invasion, especially by brome grass and leafy spurge, by the effect of repeated fires related to training activities, and by damage and erosion resulting from track vehicles such as Leopard tanks and other track vehicles. The result of these concerns was a series of studies - in the main part funded by the German army. Among the investigations were the effects of repeated fires on the native prairie and on brome grass; and the impact of tank traffic on mixed grass prairie.

Tonight I want to tell you about the tank study. In order to assess the impact of Leopard tanks on the mixed grass prairie vegetation 48, 10 x 10 m plots were laid out in undamaged prairie. Treatments were allocated in a random manner with 8 replicates of each treatment:

1 pass over the appropriated plot each week from May to September was called the every week treatment.

1 pass a week from May to September in year one, then a years rest and one pass a week from May to September in year 3 (Alternate).

1 pass each week May and June (Spring).

1 pass each week July and August (Summer).

1 pass every 3 weeks (Occasional).

Controls, no traffic.

We sampled the vegetation before any traffic on all the plots, then in mid May, early July and late August each year. We also tested the soil compaction in each plot. We were fortunate to have the cooperation of the German army who provided a Leopard tank and crew each Wednesday at 1:00 p.m. from May to September in 1986, 1987 and 1988.


  Mean Frequency of Bare Ground and
  Weed Species on Tank Plots
  at CFB Shilo, August 1989.

  Numbers in parenthesis indicate the
  total number of tank passes in three years. Chart showing mean frequency of bare ground and weed species on tank plots, August 1989.

This chart shows that the plots traversed every week and those traversed every week with a year's rest in between have the most bare ground. There is 15% more bare ground in the plots impacted in the spring than those impacted in the summer. Control plots have only about 5% bare ground. Turns show a striking increase of bare ground as the number of turns increases.



Control plots had no weeds in them but the frequency of plots with weeds increased in the same manner as the bare ground in the previous slide. This indicates that weedy species are the first to colonize bare ground. Their seeds are in the seed bank and rapidly take advantage of any opening in the (dense) prairie sward. But unlike many native species, many weeds do not have much branched fibrous root systems that help to stabilize the soil. Leafy spurge is one such example of a species that rapidly colonizes bare ground.


  Mean Frequency of Native Species
  on Control and Impacted Tank Plots
  at CFB Shilo, August 1988.

  Numbers in parenthesis indicate the
  total number of tank passes in three years. Chart showing mean frequency of native species on control and impacted tank plots, August 1988.

The frequency of native species follows the same pattern with a dramatic decrease in the frequency of native species as tank impact increases. The following year after all the plots had a year's rest two of the grasses characteristic of mixed grass prairie - blue gramma and needle-and-thread show little effect of the stress of tank impact. The same applies to prairie sage.



In contrast juniper is dramatically reduced, lichens and spike mosses are eliminated altogether on plots traversed every week and almost eliminated on the spring and alternate year plots. Although seemingly insignificant because they are small and grow close to the soil surface, they both play an important role in stabilizing the soil surface which in turn reduces erosion.

Tank Experiment Conclusions:

  • Tank traffic creates bare ground

  • Bare ground results in
    • weed invasion
    • loss of native prairie species
    • soil erosion

  • Bare ground is minimized when
    • spring traffic is eliminated
    • traffic is distributed over time
    • turning is minimal
We presented the findings of our studies to the Canadian and German military at Shilo, and after discussion they have agree:

(1) The training season for Germans will be shortened by two rotations, ie. 2 weeks in the spring and 2 weeks in the fall to allow vegetation some time to recover from the impact of traffic. The number of tanks will be 26 instead of 33, they will use 26 Marders instead of 39 - this , to allow battle runs more time to rest and regenerate vegetation.

(2) Dry training supervisors will make every effort to record any significant damage and mitigative steps will be taken (eg. leveling, roller packing and reseeding where practical). Appropriate monitoring will be conducted prior to, during and after training rotations. Satellite or other air photos will be obtained in May and November, and damage assessed.

(3) Vehicles used on battle runs contaminated with leafy spurge will not be used elsewhere on the range to reduce the spread of this noxious weed.

Changes in their training activities have been accepted by the German Army in order to reduce their impact on the natural vegetation. At Shilo, compromises have had to be accepted by environmentalists and by the army. Compromises are not necessarily a sign of weakness. At Shilo, compromises have had to occur. If all the environmental interests had been satisfied German military training would not have continued and this would mean devastating repercussions for the local economy.

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Political Will

In summary, we can say there is no political will to make the decision to do something to rejuvenate the Delta Marsh - but to say that the environment suffers because of the lack of political will means that relative to people problems the well-being of the environment has a low priority. In contrast, at CFB Shilo there has been some movement towards respecting the environment.

Political will reflects society's sense of what is important, and what should have a high priority. I think what is at the root of our collective lack of will, is our assumption that the earth belongs to us as something to be used and exploited. I suggest that until we acknowledge that we belong to the earth, it does not belong to us, we will continue to have difficulties in managing our natural resources wisely.

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Sources

Bossenmaier, E.F., ed. (1968)
The Delta Marsh: its values, problems and potentialities. Dept. of Mines and Natural Resources, Winnipeg, MB.

 

Goldsborough, G.L. (1987)
Ontogeny of a small marsh pond: revisited. University of Manitoba Field Station (Delta Marsh) Annual Report 22: 37-42.

 

Kunec, D.L. and Shay, J.M. (1990)
The effect of military activity on native mixed-grass prairie. C.F.B. Shilo, Contract Report. Dept. of Botany, University of Manitoba, Winnipeg, MB.

 

Mitchell, B., ed. (1991)
Resource management and development. Oxford University Press, Toronto, ON.

 

Rowe, S. (1990)
Home place, essays on ecology. NeWest Publ. Ltd., Edmonton, AB.

 

Shay, J.M., Gorrie, S.E., Kunec, D.L.,and McIraith, A. (1989)
The effect of military activity on mixed-grass prairie, C.F.B. Shilo. Contract Report. Dept. of Botany, University of Manitoba, Winnipeg, MB.

 

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Copyright © 1998 Dr. Jennifer Shay