How Minnesota Trees Purify Our Lakes

Nothing better describes the joy of a summer day than spending time in the great outdoors. Regardless of whether you prefer to visit one of Minnesota’s 66 state parks, spend the day at the lake, or simply enjoy the scenic views of the Mississippi River, you will encounter the benefits of two of Minnesota’s greatest natural resources: trees and water.

Minnesota trees and forests play essential roles in maintaining a healthy environment by keeping our water sources clean. Aside from creating oxygen, reducing pollution, and providing a habitat for various species, trees also naturally filter water, which is why most natural water is safe to drink. In fact, about 75% of Minnesotans get their drinking water from forested parts of the state. While this natural filtration works to keep Minnesota lakes clean and clear, it also helps cities to reduce water purification costs all while ensuring its citizens have access to safe drinking water.


The simple answer is trees purify water through umbrella, filter, and sponge effects.

  • Umbrella Effect: When it rains, the tree’s leaves act like an umbrella, guiding the rain to the ground. By guiding the water, it hits the ground softer, which then helps prevent the soil from washing away into nearby water sources. Instead, the rainwater can replenish the underground aquifers which are underground sources of water.
  • Filter Effect: Fallen leaves, needles, branches, and logs on the forest floor trap sediment, nutrients, and pollutants that are suspended in rain – filtering the water before it soaks into forest pore spaces and into the ground. For the pollutants and excess nutrients already in the ground, tree roots will filter them into the tree before they soak further downward.
  • Sponge Effect: These fallen leaves, needles, branches, and logs on the forest floor are also able to absorb rainwater and snowmelt, slowly releasing the absorbed water over time. By acting like a sponge, trees help to reduce erosion and prevent potential flooding during particularly wet seasons.


Perhaps you have noticed that the abundance of trees alongside our lakes and rivers. This greenery not only creates beautiful scenery for humans to enjoy, but also benefits all sorts of plants and animals in the water. Planting trees near lakes and rivers allows the tree’s root structures to help prevent soil erosion from contaminating the bodies of water and enhances aquatic life. For example, shade over water keeps the water cool and protects against sudden temperature changes. This is especially important for species of fish such as salmon and trout which are sensitive to water temperature and only lay eggs in cool water. Furthermore, the plant debris of waterside trees provides food, nutrients, and a habitat for many aquatic life species that would not be able to survive otherwise.

Moreover, keeping Minnesota lakes and rivers cool will impact those of us boating, fishing, or swimming in the water. As the temperature of water increases, so does the rate at which harmful bacteria spreads. Therefore, by cooling the water we also are able to decrease the spread of that bacteria, making the water safer for all parties.  


Ultimately, Minnesota’s trees and forests play an essential role in our ability to enjoy clean and fresh water, so why not help make that job easier? For those of you with cabins or lakeside houses, consider leaving a few trees on along the waterline. However, if you do not have land on or near a lake, there are still ways to contribute to a healthy environment. Here are some actions you can take today to ensure we can continue to enjoy our summers among Minnesota’s trees and water:

  • Plant a tree
  • Take shorter, cooler showers
  • Minimize the use of pesticides and fertilizers
  • Keep your trees healthy by removing dead or diseased limbs
  • Properly dispose of all waste at parks and recreational greenspaces

Minnesota’s trees are one of our greatest natural resources and without them, the Land of 10,000 Lakes would not have clean and safe water to boat, fish, or swim in. So, next time you find yourself out on the water, walking through the forest, or looking at the trees in your yard, take a second to appreciate what trees do for our water systems. If you have any questions about keeping your trees healthy contact us and speak with one of our tree specialists today.