The Lake Simcoe Region Conservation Authority

Riverine Flood Status
Flood Outlook
Lake Simcoe Shoreline Status
Low Water Status

Single Biggest Threat to Lake Simcoe

The Single Biggest Threat to Lake Simcoe

If we told you the single biggest threat to Lake Simcoe is Phosphorus, we’d only be telling part of the story.

The truth of the matter is Lake Simcoe faces a number of very challenging issues whose impacts compound one another … trying to address any one issue without consideration of the others  will not bring about the results we need. We must take a holistic approach to fully understand, and therefore address, the issues we’re facing.

Limnologist Dr. Brian Ginn, or as you may know him, the Lake Doctor, and our team of experts, use hundreds of indicators to determine the current health of the Lake, identify emerging threats and create lake management strategies to protect Lake Simcoe.

Based on these scientific indicators, we know that Lake Simcoe is facing three significant challenges.

The good news is that lake health has been slowly improving. We have to remember it took over 150 years for the damage to get to this point, so we can’t expect the Lake to return to a state of perfect health in only a few years.

Climate Change

Climate change is a global issue, but we’re also seeing changes locally. We’re seeing a longer warm water period in the lake, increases in deep water temperatures, a shorter ice season and increased severe weather events.

It’s important to note that there are a number of biological processes that are tied to annual changes in lake temperatures, in particular. Changes in lake ice could alter the timing of temperature changes that can alter the relationships between predators and prey. For example, early or late temperature changes can leave young fish with no prey to eat at key stages of development.

This example shows only a tiny snapshot of what’s happening in the Lake, and will continue to happen  as the local climate continues to change. 

Read more about Climate Change in the Lake Simcoe watershed

Did You Know?

We're preparing a climate change mitigation strategy to reduce greenhouse gas emissions across the watershed. Results from this report are planned for release in 2020.


Phosphorus loads have decreased since the 1980s but we’re facing some new challenges around the sources of phosphorus loads. These challenges are driven in large part, by climate change and increasing urban development which can result in more urban run-off from storms and melting snow. “Loads” refers to the amount of phosphorus entering the lake from all sources.​​

This means that a wet year with multiple snow melts, rain falling on frozen ground, and high levels of precipitation​ will lead to higher river flow that increases phosphorus loads entering the Lake. These increased loads can lead to more aquatic plant growth.

Read more about Phosphorus Loads in Lake Simcoe

Did You Know?

31% of phosphorus entering Lake Simcoe comes from urban areas. Urban areas account for only 12% of the Lake Simcoe watershed. Find out about our new and innovative phosphorus offsetting policy and how it will help protect the Lake.

Invasive Species

Invasive species like quagga mussels and starry stonewort can wreak havoc on the Lake. Quagga mussels, for example, are greatly affecting species diversity and changing the Lake’s food web. We’ve been researching these impacts for the past 11 years but the new kid on the block is the invasive starry stonewort.

Starry stonewort was first discovered in Lake Simcoe in 2009 and continues to spread. This invasive is particularly worrisome as it will completely change aquatic plant diversity and change shallow water habitat. Most concerning is the inability to effectively get rid of this plant – it doesn’t respond to any herbicides – and it is very fast growing. In summer, it can double in amount every 2 – 3 days! In fact, if herbicides are used to kill off other aquatic plants, that only serves to give starry stonewort a greater opportunity to take over.

Read more about starry stonewort

Did You Know?

Starting this summer, our Lake Doctor, Dr. Ginn, and his team will begin an annual plant survey to monitor aquatic plants and detect invasive species. This annual survey is funded by Lake Simcoe Conservation Foundation thanks to the donations from generous watershed residents.

It's Not All Doom & Gloom

Despite the challenges we’ve mentioned, over all, the news is good. Lake Simcoe’s health is improving. Of course there’s still a lot of work to do.

The Lake is part of a complex ecosystem and improvements will take time. Through our research, planning and restoration efforts, we will continue to address the underlying problems, and not just the symptoms.​​​​

Get to Know the Lake Doctor

Brian Ginn has been the Limnologist for LSRCA since May of 2008. He earned his PhD from Queen’s University and is one of only three Certified Lake Managers in Canada. Studying the environmental changes in Lake Simcoe and its biological communities, he applies his research to help set realistic and effective management strategies for the lake. 

Questions about the health of Lake Simcoe? Submit your question below and we’ll get back to you!

Brian Ginn

Did you know Lake Simcoe is the cleanest lake in the Great Lakes Region?

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