The second Sources of Knowledge Forum, held in Tobermory in 2010,  explored Wildlife and Its Value to Community. One notable contribution that has relevance today was from the Nature Conservancy of Canada (NCC) who presented their Conservation Plan for the Northern (Bruce) Saugeen Peninsula.

The NCC stated that the Peninsula is “World renowned for its diversity of orchids (42 species) and ferns (20 species), this region is one of the Great Lakes’ biodiversity “hotspots” … many unique habitats occur, including alvars, sand beaches, fens and meadow marshes. Along its eastern shore, the Peninsula supports a rare example of an ancient forest, with an Eastern White Cedar that is 1,320+ years old. It is the oldest living tree in Ontario and quite possibly Canada.

Another unique feature of the Saugeen Peninsula is that it represents the largest remaining forested area in southern Ontario. According to the Southern Ontario Land Resource Information System, in 2008 the area contained 66,146.7 ha of forest cover, representing 69.15% of the total area. But today, southern Ontario has only about 25% forest cover, which is less than the minimum needed to support healthy wildlife and ecosystems. Southwestern Ontario has only 12.1% forest cover. See Environmental Commissioner’s Report 2018.

Just before the Ford government axed the position, the Environmental Commissioner of Ontario issued the 2018 Environmental Protection Report. The report stated that before European settlement, the landscape of southern Ontario was almost continuously forested.

The Report sets out the forest cover thresholds and corresponding consequences for biodiversity and aquatic systems within a watershed. These are:

  • 30% Minimum forest cover threshold is a high-risk approach that may only support less than one half of the potential species richness, and marginally healthy aquatic systems.
  • 40% Minimum-risk approach that is likely to support more than one half of the potential species richness, and moderately healthy aquatic systems.
  • 50% Low-risk approach that is likely to support most of the potential species and healthy aquatic systems

While we no longer bulldoze entire woodlands as a matter of course, the Report notes that forest loss in southern Ontario is death by a thousand cuts. We allow other land uses to fragment the forest and nibble away at the edges. Each incremental loss has big impacts on the services the forests provide to society and the wildlife they support. When a road cuts through a woodland it not only removes forest, it creates new forest edges, which can have negative impacts on interior forest-dwelling species.


For communities with little forest cover, every small patch of forest counts as a defence against  erosion, storm water run-off, air and water pollution, greenhouse gas emissions, noise and heat. A mature, diverse forest provides functions and services (seed sources, pollen, healthy soils for regeneration, greater biodiversity) that new plantations won’t be able to provide for decades.

One of the problems is that Ontario’s land use planning rules are weak and do not prohibit clearing forests and development tends to take precedence. The key document is the Provincial Policy Statement (PPS) which sets out the general rules for land use planning in southern Ontario. Municipalities then apply these rules in their respective official plans, which must be consistent with the PPS. The PPS prohibits development or site alteration in “significant woodlands” (identified and designated by municipalities) unless it has been demonstrated that there will be no negative impacts on the natural features or their ecological functions. The PPS directs that nothing in its natural heritage policies is … intended to limit agricultural uses to continue. To protect woodland from development it must be identified and designated as significant. Small forest clearance may not be considered significant but cumulatively it probably will and in Bruce County, at least, the planners do not measure cumulative impacts.

If overall forest cover is low across the municipality, the ministry guidelines recommend that even small woodlands be considered significant, but if overall forest cover is higher, the size threshold for significance is also higher.

To increase forest cover to 40% as well as meet Canada’s carbon reduction targets,  control flooding, protect shorelines and reduce erosion, in 2008, the Ontario government created the “50 million Trees Program.” As of this year, 27 million trees have been planted across Ontario. Last month the Ford government announced that it was immediately cancelling the program to save the $4.7 million in costs. After a major nursery operation pointed out that they alone would be obliged to destroy more than three million seedlings and young trees, the Minister backtracked and postponed cancellation for a year. At the same time the government cut in half the funding for conservation authorities for flood control.

Since the start of its involvement on the Saugeen Peninsula the NCC has protected 5,865 hectares (14,490 acres). This is land permanently removed from development. Added to the National Park and other protected areas this amounts to a significant increase in protected lands in the 20 years since the NCC first bought property on the Peninsula. Nevertheless, it is worth the effort because, as the NCC pointed out at the Forum 2010, the Peninsula …represents an ecosystem of global importance for biodiversity conservation … and it provides …one of the last opportunities to protect large-scale functioning ecosystems in Southern Ontario.

In case there is any doubt about the importance to humanity’s continued existence on this planet one should read the UN Report published in May on the destruction of biodiversity and ecosystems. There is a summary here.

There is also a description of the protected areas on the Peninsula illustrated with excellent maps by the Wildlands League here.


Saugeen Peninsula

430 Million years of history

At the 2013 Sources of Knowledge Forum professional geologist Daryl Cowell, who lives in Tobermory, gave an excellent presentation describing the last 10,000 years of the history of the Great Lakes and the Saugeen Peninsula in particular.

Hundreds of thousands of tourists are attracted every year to the Peninsula, drawn to the stunning scenery and the possibilities of amusement on the clear water of Lake Huron and Georgian Bay. The foundation of the spectacular views, the clear water and the unique flora and fauna are the rock formations shaping the peninsula and the islands scattered throughout Fathom Five National Marine Park.

Image by Daryl Cowell. Click here for more detailed maps and information

The Saugeen Peninsula is part of the Niagara Escarpment, which reaches from Niagara Falls to Manitoulin Island and, indeed, in a great arc to Wisconsin. It began roughly 430 million years ago as a barrier chain of sponge-cored reefs that had built up on the floor of an ancient tropical sea teeming with marine life. Over millennia rivers laid down sediment and sea creatures died and were deposited on the sea floor, gradually building up layers of lime-rich sediments. Beneath these lime-rich sediments were older layers of sediments including muds, silts, sands and other lime-rich materials, deposited within a large depression on the pre-existing 2.5 billion year old bedrock. This part of the Canadian Shield forms a gigantic bowl encompassing lakes Michigan, Huron and Georgian Bay, and Erie. It is known as the Michigan Basin and it comes to the surface north of Manitoulin Island. As you drive north of Little Current you can clearly see where the sedimentary rock of the escarpment ends and the Canadian Shield comes to the surface.

In time, magnesium in the saline surface waters replaced some of the calcium in the underlying lime-rich sediments, converting them to the dolomite mineral, eventually hardening to form dolostone, which characterizes the present day Saugeen Peninsula. Dolostone is the dominant rock type on the surface of the peninsula, however shales (from mud), siltones (from silts), and other dolostones appear beneath the escarpment crest on the slopes leading to Georgian Bay. The ancient sea supported sponges, corals and a variety of shelled organisms which gradually built up an enormous reef, which, apparently, would have rivalled Australia’s Great Barrier Reef. The evidence of these ancient life forms can be found in abundant fossils in many parts of the peninsula.

In geological time, the period when the bedrock now forming the peninsula and the islands were formed is known as the Silurian. Throughout that time, climate and ecosystem changes occurred which caused the nature and frequency of the sedimentary deposits to change and these changes are visible today in the differences in the rock layers. North of Wiarton, the dolomite rock generally falls into three main “age groups” although other, older, pre-Silurian formations are visible lower down on the cliffs facing Georgian Bay. The oldest outcrops on the surface of the peninsula mostly occur at Cabot Head, Cape Croker, and Colpoys Bay. These rocks belong to the Cabot Head Formation. Lying above the Cabot Head Formation and spreading west approximately to the Bury Road and south of Cabot Head is a younger layer called the Gasport/Goat Island formations and on the west side of Bury Road to shore of Lake Huron is the youngest rock type belonging to the Guelph Formation.

The dolostone rock is pitted, often with perfectly round holes. These holes, called “pit karren”, have been formed by rainwater opening up pre-existing pores in the bedrock surface which are subsequently expanded by acids secreted from plants colonizing the rock surface. This is a type of karst landform feature which results from the solution of certain types of bedrock by weak acids in rain and from living vegetation. Karst is a suite of landforms created by solution and enhancing the subsurface movement of water  

through sinkholes, cracks and caves down to less soluble rock layers (e.g., shales). There are, for example, sinkholes and cracks which transport water accumulating in the area of Cape Hurd Road and Hwy 6 rapidly via a series of sinkholes into Georgian Bay at Dunks Bay.

Dolostone is not the only rock on the peninsula and the Islands. All over the surface of the peninsula one can find rocks which definitely do not belong. These are known as ‘erratics’ and they have been scooped up in the north and carried huge distances to the area by the glaciers during various ice ages. The glaciers also scooped out the lake basins to great depth so that all the lakes with the exception of Erie, have depths which are well below sea level and could not, therefore, have been carved out by the action of rivers.

The iconic landform in the Fathom Five Marine Park are the structures on Flowerpot Island. Wave action and falling water levels over years have eroded away weaker rock underlying thicker, stronger rock leaving behind rock pedestals which have the locally famous flowerpot shape. The large flowerpot on the island started to form roughly around 3,000 years ago.

A detailed account of the bedrock geology of the Saugeen Peninsula called Memoir 360, Paleozoic Geology of the Bruce Peninsula Area, Ontario by B.A. Liberty and T.E. Bolton

is available from the Geological Survey of Canada, at:

The surface geology of the peninsula including the types of soft sediments can be found in a more recent Open File Report, Surficial Geology of the Bruce Peninsula, Southern Ontario by W.R. Cowan and D.R. Sharpe from the Ontario Geological Survey, at:

A more readable and beautifully illustrated account to which Mr. Cowell made a major contribution is: Geology and Landforms of Grey & Bruce Counties by The Bruce-Grey Geology Committee. This can be ordered from the Ginger Press in Owen Sound.

Plastic Waste

On March 10 this year the Province of Ontario announced that it was considering a ban on plastic waste as part of a broader strategy to send less waste to landfill sites. Almost one tonne of waste per person is generated annually in Ontario and only 30 per cent is diverted from landfills by composting and recycling. According to the government this rate of diversion has not changed over the last thirty years. The Environment Minister Rod Phillips has said, “Plastics is a priority from our government’s point of view, particularly as we talk about plastics in our waterways.” The government estimates that almost 10,000 tonnes of plastic debris enter the Great Lakes each year.

In a February 2017 report by the International Joint Commission (IJC), the Canada/USA body that manages the lakes, studies have documented the occurrence of plastic debris, including plastic bags, bottles, boxes, fibres, micro-beads, and cigarette butts, in marine and fresh waters including the Great Lakes. Larger plastic debris degrades into smaller micro-plastics, and it is these smaller particles that are of particular concern. Micro-plastics generally refer to particles 5 mm or less in size and include; micro-beads from personal care products; fibres from synthetic clothing; pre-production pellets and powders; as well as degraded pieces from larger plastic products. Little is known about the fate of these smaller plastic particles and the IJC is concerned about their potential impacts on environmental and human health.

Plastic enters the Great Lakes in many ways. Most egregiously, people on the shore and on boats throw litter in the water but micro-plastic pollution also comes from wastewater treatment plants, storm water and agricultural runoff. Some plastic fibres become airborne, possibly from clothing or building materials weathering outdoors and these are probably deposited into the lakes directly from the air.

The IJC made 10 recommendations, one of which was to develop a model to determine the sources and fate of micro-plastics. In their Aug 20 2018 issue, The Conversation, an independent, not-for-profit media outlet, reported on the work of two scientists, from the Rochester Institute of Technology, Matthew J. Hoffman and Christy Tyler, who have developed a computer model to track the movement of micro-plastics in the lakes.

They found that, while plastics often accumulate in large floating garbage patches in the oceans, in the Great Lakes there may be temporary accumulation patches but they do not persist as they do in the ocean. In Lake Erie and the other Great Lakes, strong winds break up the accumulated patches and there was no evidence for a Great Lakes garbage patch. This appears to be good news except that we know that a lot of plastic is entering the lakes so if it is not accumulating in large patches, where is it?

Hoffman and Tyler’s computer model shows that most of it ends up closer to shore (see map below.) This helps to explain why so much plastic is found on Great Lakes beaches. In 2017 alone, one group of volunteers collected more than 16 tons of plastic at beach cleanups. Thus, the plastic is ending up near shore, where more wildlife is located and where we obtain our drinking water.

Average density of simulated particles in the Great Lakes from 2009-2014. Notice that there are no patches in the middle of the Lakes, but more of the particles are concentrated near the shores. Credit: Matthew HoffmanCC BY-NC-ND

The scientists estimate that over four tons of micro-plastic are floating in Lake Erie. This figure is only a small fraction of the approximately 2,500 tons of plastic that they estimate enters the Lake each year. According to their initial simulations, much of the plastic is expected to sink. This prediction is supported by sediment samples collected from the bottom of the Great Lakes, which can contain high concentrations of plastic. You can see the computer simulation of the dispersal of micro-plastics in Lake Erie here.

Another IJC recommendation was to assess the potential ecological and human health impacts of micro-plastics in the Great Lakes. One such recent study – available here.

The researchers found micro-plastic particles – fragments measuring less then five millimetres – in tap water and beer brewed with water from the Great Lakes. Since many studies indicate risks to human health when plastic particles such as synthetic polymers are ingested, clearly more needs to be known about the presence and abundance of micro-plastic particles in human foods and beverages. The PLOS study investigated the presence of micro-plastic particles in 159 samples of globally sourced tap water, 12 brands of Great Lakes beer, and 12 brands of commercial sea salt. Of the tap water samples analyzed, 81% were found to contain micro-plastic particles. The majority of these particles were fibres (98.3%) between 0.1–5 mm in length and there was an average of 5.45 particles per litre. Plastic debris was also found in each brand of beer and salt. Of the extracted particles, over 99% were fibres. The average number of particles found in beer was 4.05 particles per litre and the average number of particles found in each brand of salt was 212 particles per kg. Based on consumer guidelines, the study indicated that the average person ingests over 5,800 particles of synthetic debris from these three sources annually, with the largest contribution coming from tap water (88%).

The IJC also recognized that it is vital to change peoples’ behaviour and the only way to do that is through education. They recommended that Canada and the USA increase their funding of education programs, particularly for grades K to 12.

Tobermory Seiches

A Review of a study by John Greenhouse

A seiche (SAYSH) is a wave in an enclosed or partially enclosed body of water. Like water in a jostled tub, energy sloshes back and forth between the boundaries of the water body creating what are known as “standing waves”, not unlike those that can be seen in a skipping rope. Seiches and seiche-related phenomena can be observed on lakes, reservoirs, bays, harbours and oceans. Some can be very dramatic, but others are all but imperceptible.

On the Great Lakes a seiche derives its energy (the “jostling”) from the atmosphere. A sharp change in pressure or wind speed will produce a wave in the body of water (Figure 1). The wave is reflected repeatedly from the shores, generating standing waves with one or more peaks. The repetition time, or “period” of the oscillation is determined by the size and shape of the water body, and by its depth.  In large water bodies the period of oscillation will be several hours. As shown in Figure 1, the thermocline can also oscillate as a standing wave.

Figure 1. Wind generating standing waves on the surface and the thermocline of a lake.
Frankemann [CC BY-SA 3.0 (

In bays leading off Lake Huron the water level will rise and fall with the lake, but they also have oscillations with periods determined by the size, shape and depth of the bay itself. These harbour oscillations or seiches, have periods typically from a few minutes to an hour.

Large seiches occur every few years and, are exceptional events. They are generated by extreme weather out in the big lake and, when they arrive at a harbour, they can be hugely amplified. They are extreme events but a seiche is continual. The lake and its harbours are in almost constant but very low level oscillation because the atmosphere itself is never completely static. This continual seiche activity is most often imperceptible to observers on land or in boats due to the extremely long period and low amplitude of the wave.

John Greenhouse is fascinated by these harbour oscillations. They have already been studied quite extensively but there are nothing more than anecdotal accounts of the seiche activity in individual bays and harbours around the peninsula. Do they have characteristic and repeatable periods independent of the those in Lake Huron itself? Are these characteristics explainable in terms of the size, shape and depth of bays? Do these characteristics determine what happens when a major seiche comes from the big lake outside? Despite an extensive body of literature on the subject, there seemed to be a local knowledge gap to fill.

Figure 2. Numbered red dots indicate the location of measuring stations in this study.

Accordingly, over a four year period, John Greenhouse set up water-level monitoring stations (Figure 2) at 19 locations in Tobermory and along the western shore of the peninsula.

The frequency of a wave is the number of times per second that the wave cycles. Frequency is measured in cycles per hour (cph). The period of the wave is the time between wave crests. The period is also measured in time units. The period and frequency are inverse of each other. Frequency, the inverse of period, is measured in cycles per hour (for example, 4 cycles per hour implies a period of 15 minutes).

John has characterized each harbour in terms of the frequency of its oscillations. He found that each harbour had its own characteristic frequency that was consistent over time and it was unique to that harbour. In other words, each harbour or bay had its own “signature”. 

The dominant frequency of the harbours he studied ranged from 0.8 cph at Stokes Bay (period of 75 minutes) to 13 cph (period of 4.5 minutes) at Little Tub Harbour.  These harbour frequencies are broadly consistent with predictions based on the size, shape and depth. They are quite distinct from oscillations in the big lake, which also can be measured in the harbours but have much longer periods.

As noted above, a large seiche coming in from the lake can hugely amplify a seiche in a harbour like Little Tub with possibly damaging effects. The next step in this study may be to obtain simultaneous measurements of a large seiche on the lake before it reaches the harbour and measure the harbour’s response. From that one might be able to predict a large seiche and mitigate the effects on property.

The full paper will soon be published on the SOK website (www.sourcesof In the meantime you might enjoy reading Chapter 7 of Sherwood Fox’s book, The Bruce Beckons, who gives a wonderful description of  a very large seiche in Stokes Bay in the late 1940’s.

SOK Talks

Sources of Knowledge is not just about the annual forum. It has also been running a series of evening talks at the Park Visitor Centre auditorium. On March 13, 2019 at 7pm, Brian McHattie from Parks Canada will be giving a talk on: Iconic West Coast Orca Population in Crisis.

Fathom Five National Marine Park – Conservation Options

Fathom Five is a 114 km2 freshwater, protected area located on Lake Huron at the top of the Saugeen Peninsula. It was established as a provincial park in 1972 to protect sunken shipwrecks. Then in 1987, along with the regional islands of Georgian Bay Islands National Park (e.g., Flowerpot Is.), Fathom Five became the first site to be managed under the stewardship of Parks Canada’s national marine conservation area program.

The 2013 Sources of Knowledge Forum on “Changing Lakes” featured Scott Parker, a climate change ecologist with Parks Canada. Dr. Parker made the case for adopting a “resilience” approach to lake conservation as opposed to a traditional management approach.

Ecological resilience is the ability of an ecosystem to cope with disturbance and retain defining structures, functions and feedbacks. Whereas a traditional management approach may focus on resisting change, maintaining historic conditions or promoting system efficiency (e.g., maximum sustainable yield, single stable state), resilience prepares for disturbance by enhancing adaptive capacity and system diversity.

Today, Lake Huron is arguably a novel ecosystem, a system that no longer resembles its historic state in terms of composition and function. It’s a challenging context for conservation, and management approaches focused solely on maintaining or restoring the abundance of native species may simply be untenable. It is here that resilience creates space for discussing conservation goals based on ecosystem structure and function, and on disturbance and adaptive capacity.

In 2013, Dr. Parker found that much of the current change in the offshore ecosystem was coincident with the invasion of quagga and zebra mussels. This most recent disturbance followed an earlier invasion of sea lamprey and alewife and period of over-fishing which contributed to the near lake-wide extirpation of lake trout and loss of four of the six deepwater cisco species (two are extinct). The subsequent decline of the sea lamprey and alewife created favourable conditions for native lake trout and cisco to recover. However, their recovery was limited because the newly established mussels had played a role in making the lake less productive. Coincidently, one of the primary lake bed crustaceans, Diporeia spp (a tiny shrimp-like organism) a major food item for whitefish and other fishes, was experience a population collapsing. Together, these impacts contributed to a break in traditional transfer of energy and nutrients back into the water column. Thus, after the recovery from the sea lamprey and alewife invasion the lake, although resilient as shown by the return of the native species, did not return to its original state. Further, the subsequent dominance of invasive quagga and zebra mussels has virtually eliminated any prospect of restoring this ecosystem to its historical composition. It appears the offshore ecosystem of Fathom Five transitioned to a resilient although less-desired state.

As to the coastal areas there was, in 2013 a widespread concern with low lake levels, which by 2012 had approached twelve years of sustained low levels as compared with a maximum period of five years during the past century. Non-native species, including round goby, common carp, and Eurasian watermilfoil were present and had the potential to impact some coastal areas. In spite of this, in 2013 Dr. Parker felt that the coastal ecosystem of Fathom Five appeared to be in a resilient and desirable state.

There are a number of impediments to adopting a resilience approach to conservation. The relatively small size of Fathom Five (114 km2) and limited connectedness with other protected areas in Lake Huron makes aspects of resilience, such as protection of representative biodiversity and facilitation of disturbance recovery, more challenging. Secondly, governance of the lake is complex involving a multitude of organizations, stake-holders and rights-holders, such as Parks Canada and other federal department’s the Province, and the Saugeen Ojibway Nation.

In 2013, Dr. Parker felt that it was an opportune time for Fathom Five to consider incorporating resilience within its planning and management processes. Now, six years later, the topic of this years’ SOKF is intended to focus on whether the expectations for Fathom Five have been met and what should be its future. Accordingly, Dr. Parker’s 2013 observations and prescriptions for the lake are relevant. At the Forum on May 3 to 5 of this year, Dr. Parker, together with Cavan Harpur, Parks Canada Ecologist will be offering an update of resilience in their presentation entitled: But Doth Suffer a Sea Change, Into Something Rich and Strange: An Update on the State of the Fathom Five Ecosystem

Great Lake Water Levels – The Long View

The Sources of Knowledge Forum (SOKF), a charitable non-profit organization based in Tobermory, was founded to inform local people and a wider general public about the unique environment that is the Saugeen Peninsula and its surrounding lake. SOKF hosts an annual, three day public seminar in Tobermory to highlight some aspect of this environment. SOKF also has a responsibility to extend its reach and to develop a model for a larger knowledge network. With that in mind SOKF is starting a monthly blog to highlight current issues and resurrect topics from previous forums which are relevant today.

The next annual forum, on May 3 to 5, 2019, will focus on Fathom Five National Marine Park. Ten years ago, as part of the first forum, Steve Blasco of the Geological Survey of Canada, gave an overview of the history of Lake Huron since the end of the last ice age 12,000 years ago. Over that period the lake levels have changed dramatically. There have been at least three extremely low water level episodes and three high ones. 4500 years ago, the Peninsula, including the cliffs along the Georgian Bay shore, was almost submerged.

Between 10,000 to 7,500 years ago the lake levels were generally low and forests grew on what are now the lake beds of Lake Huron and Georgian Bay. Today the remains of those forest are known as the “drowned forest’ because the trunks are still rooted on the land where they originally grew. Those dramatic changes in lake levels, varying by as much as 125 meters, were caused by the receding glaciers of the last ice age, which allowed the land, freed of the weight of the ice, to spring upwards. Climate changes also played a role as did the way the lakes drained into the sea. Originally, the Mississippi was the preferred route to the sea. Ten thousand years ago the lakes drained through the Pettawawa/Ottawa rivers into the St. Lawrence.

Today’s modest changes in the lake levels (as much as two meters) have two principal causes, precipitation (including run off) and evaporation and these are the result of weather. Water levels rise and fall in seasonal cycles, with annual highs typically occurring in the summer and annual low levels in winter. Water levels also fluctuate in longer cycles in response to persistent wet or dry conditions that may last for a number of years. Declining annual ice cover and warmer water temperatures increase the potential for evaporation when water is open and there is a large difference between air and water temperatures. A mild winter produces less evaporation.

Inevitably, humanity has an impact on lake levels, although they are much less than is often believed. Since the late 19th century, Lake Michigan-Huron has been lowered by about 16 inches due to dredging and other channel changes in the St. Clair and Detroit Rivers. The International Joint Commission (IJC), which manages the Great Lakes on behalf of Canada and the US, published a study in 2012, which found that erosion since 1962 had caused another 3 to 5 inches of lowering. However, the erosion is not ongoing. The effect of the diversion at Chicago has removed the equivalent of lowering the Lake Michigan-Huron by about 2 inches whereas the Long Lac and Ogoki diversions into Lake Superior have raised Lake Michigan-Huron by the equivalent of 4 inches..  The table below illustrates humanity’s impact.

Human Impacts on Lake Levels

                                                        Long Lac 
and Ogoki
Chicago WellandNet Effect
+ 0.06 m

– 0.02 m

– 0.02 m

+ 0.02 m
Michigan / Huron
+ 0.11 m

– 0.06 m

– 0.06 m

– 0.01 m
+ 0.08 m

– 0.04 m

– 0.13 m

– 0.09 m
+ 0.07 m

– 0.03 m


+ 0.04 m

  International Joint Commission

Because of climate change, the IJC admitted that there is considerable uncertainty regarding future trends in Great Lakes water levels. In short, the 2012 IJC study indicates that over the next 30 years, lakes Superior, Michigan, Huron and Erie levels are likely to go down – but they may go up.

You can find the full, 236 page report at