What are the 4 main types of freshwater ecosystems?

Rivers, creeks, lakes, ponds, and streams are all freshwater habitats. So are wetlands like swamps, which have woody plants and trees; and marshes, which have no trees but lots of grasses and reeds. Freshwater accounts for only three percent of the world’s water. (The rest is saltwater.) But despite that tiny amount, freshwater habitats are homes for more than 100,000 species of plants and animals.

Fish living in freshwater habitats have plenty of company. Snails, worms, turtles, frogs, marsh birds, mollusks, alligators, beavers, otters, snakes, and many types of insects live there too. Some unusual animals, like the river dolphin and the diving bell spider, are freshwater creatures. Plants such as algae, cattails, water lilies, and aspen and willow trees help keep the water clean by using their root systems to filter pollution and excess nutrients from the water.

Lakes are formed by different acts of nature. Many appeared after glaciers moved across Earth during the last ice age, between 12,000 and 1.8 million years ago, and left giant bowl-shaped hollows in the land that filled with rainwater and runoff. Others were created when Earth’s crust shifted, leaving grooves and ridges to catch water. And sometimes when a volcano erupts, all the magma flows out. If the land collapses into the empty crater, it leaves holes that can turn into huge lakes. Crater Lake in Oregon was made this way.

Rivers are created when melting snow or ice runs down mountains, following the grooves and channels of the land on the way to the sea—rivers always flow to an ocean. Wetlands, areas where the land is covered with water most of the time, often form in the land surrounding rivers that flood, or in areas where groundwater seeps up through the bedrock underneath the soil. Bedrock is made of different types of rocks like granite, sandstone and limestone. Water can seep through the cracks between these rocks, and it can dissolve limestone. Beavers can even create wetlands by building dams on rivers and streams.

The largest freshwater habitat in the world is the Everglades, a 1.5 million acre wetlands in southern Florida. The Amazon River in South America begins in the Andes Mountains and goes 4,000 miles (6,400 km) to the Atlantic Ocean; it flows through six countries, including Peru and Ecuador. Lake Baikal in Siberia, a region in Russia, is the world’s biggest lake. This North Asian body of water contains one-fifth of all the freshwater on the planet.

So whether you’re a hungry turtle, a pollutant-sucking plant, or a thirsty human who also likes to play in the water, freshwater habitats are vital ecosystems for our planet!