Planet Earth should be called Blue Planet or Planet Water. The reason is obvious. Just look at it!

Among all water in the planet drinkable water is rare. Since 97.5% of the water is found in the ocean and is too salty to drink or use to water crops, which leaves us with only 2.5% of fresh water, with few dissolved salts. Yes, there is desalination technology to remove salt from sea water and have fresh water. This process is used by many countries and cities but it is really expensive. I can talk more about it on another post.

Since most fresh water is tied up in glaciers, icecaps and underground aquifers, just over 1 part in 10,000 of Earth’s water is easily accessible for human use.

Glacier - forms in locations where the mass accumulation of snow and ice exceeds ablation over years. As they move and flow they shape the landscape

Ice caps - bodies of ice located at the earth's poles. More stagnant than glaciers, it's land area is less than 50 000 km². Land areas with more than 50 000 km² are ice sheets

Water constantly moves among the reservoirs via the hydrologic cycle. As it does so it distributes heat, erodes mountain ranges, builds river deltas, maintains organisms and ecosystems, shapes civilizations, and also gives rise to political conflicts.

As water physically shapes Earth’s landscapes, fresh water systems support a large fraction of our planet’s organisms. Several freshwater ecosystem types can be thought of as the aquatic equivalents of biomes.

On this post I will start talking about these freshwater systems. Despite the fact that they are not that many, there is a lot to talk about each of them, so I’ll talk about them one post at a time.

The freshwater systems are:

  • Glaciers;
  • Lakes and ponds;
  • Rivers and streams and
  • Underground aquifers

As a whole, you’ll find in the next few posts things like:

  • The importance of freshwater systems to us, human beings;
  • The importance of freshwater systems to ecosystems that depend on them;
  • How freshwater systems relate to the ecosystem as a whole. For instance, why cutting the trees on water bodies margins cause erosion, sedimentation, droughts and floodings among many other problems;
  • How freshwater systems affect one another, since they are connected.
  • What actions we take that can affect these freshwater systems and the ecosystems related to them;
  • How our actions affect freshwater systems and the ecosystems related to them;
  • The consequences of anthropogenic actions and what can be done to prevent them.

Freshwater ecosystems – Rivers and Streams

Rivers and streams are formed by water from rain, snowmelt, or springs that run downhill and converge where the land dips lowest, forming streams, creeks, or brooks. Such water courses merge into rivers which, eventually, reach the ocean or a landlocked water body.

The landscape is shaped by the rivers and areas flooded by rivers periodically are said to be within the river’s floodplain.

Agriculture thrives in floodplains because its soil is fertile due to the deposition of silt from floodings.

Waters of rivers and streams host diverse ecological communities and riparian (riverside) forests, that are productive and species-rich.

Like any other ecosystem, the rivers and riparian forests depend on each other to survive. Without the river and stream the soil isn’t fertile enough for the riverside forest to exist.

The riverside forest, on its turn, is important to the river because:

1. Riparian forests maintain the high water quality needed for supplying drinking water and maintaining diverse forms of aquatic life.

Nitrogen and phosphorus are found naturally in the environment and are necessary for aquatic plants and algae to grow and reproduce. However, excess nitrogen and phosphorus can be very damaging to the aquatic environment.

Because of human activities phosphorus and nitrogen are also found in fertilizers, septic leachate, sewage treatment plants, urban runoff, detergents, road dust, grass clippings, and yard debris.

When such nutrients are found in excess they can cause the rapid growth of algae and aquatic plants, which can reduce the amount of light penetrating the water and provoke death to aquatic plants and fishes. This process is called eutrophication.

When this algae dies, it’s decomposed by bacteria that use oxygen, lowering the amount of oxygen in the water. The depletion of oxygen causes taste and odor problems in drinking water and can also cause fish and other aquatic organisms to die or move.

Organisms that thrive in low oxygen environments release hydrogen sulfate and methane, chemicals that can be toxic to aquatic life and can compound the problem of an oxygen-deprived environment.

2. Riparian forests act as nutrient filters, sinks and transformers to help reduce the amount of nutrients reaching streams. Since most phosphorous is bound to small soil particles and both are filtered down, the remaining that is not soil bound is not removed by filtration, but by other mechanisms:

Riparian forests function as a nutrient sink. They sequester nitrogen and phosphorus in biomass and improve the ability of soils to hold nutrients by adding organic material to the soil. As water flows over the surface or as groundwater moves within the root zone of riparian plants, the plants actively uptake nutrients and absorb them. This plant material is removed from the riparian forest when it’s eaten or incorporated into animal biomass.

Studies have shown that riparian forests can remove a lot of nitrate (a form of nitrogen) and

phosphorus from agricultural runoff. The storage of these nutrients in the riparian forests reduces the amount of nutrients reaching streams and lakes. I would like to give you an idea in numbers for the amount of nutrients removed by the riparian forests, but these numbers seem to vary from area to area, influenced by the type of soil, climate, types of flora and other characteristics.

Here is a study from Iowa State University; and here an article about the importance of riparian forests that are examples of these studies for the amount of nutrients removed by the forests.

Riparian forests act as nutrient transformers as they change the chemical composition of nutrient compounds. When soil moisture is high enough to create anaerobic conditions in surface soil layers, bacteria can convert dissolved nitrate do gaseous nitrogen, releasing it safely into the atmosphere and reducing the amount reaching streams.

Here you can find a an interactive animation of the nitrogen cycle that I find it really interesting!

They are also capable of transforming toxic chemical and pesticides to nontoxic forms through microbiological decomposition, oxidation, reduction, hydrolysis, and solar oxidation.

3. The conservation of riparian forest is important in stabilizing stream banks, reducing erosion, and providing high quality wildlife habitat.

Stream banks are stabilized by the riparian forests deep root systems, which hold the soil in place and provide a degree of roughness capable of slowing runoff velocities and spreading flow during storms.

Riparian forests help prevent erosion of stream banks and the production of sediments. Without forest buffers, stream flow scours the streambed and banks leading to bank erosion and channel straightening. Straight channels lead to accelerated stream flow velocity and additional stream bank erosion, leading to the development of wide shallow streams with elevated temperatures and a low diversity of aquatic species.

4. Riparian forest helps on the maintenance of proper stream temperature and a healthy ecosystem.

Rriparian forest forms a canopy, that shades the stream. The shade moderates water temperature and protects it against fluctuations in temperature that can be detrimental to the stream ecosystem’s health.

Elevated temperatures reduce the amount of dissolved oxygen in the water and reduce fish spawning and survival. Studies have shown that, for example, when stream surface shade is reduced to 35%, trout population drop as much as 85%.

The amount of light reaching the stream also affect the types of algae produced in the stream. The type of algae growing in wooded areas are different from the ones in the open sunny areas. Fish eat macroinvertebrates and they prefer to eat the algae growing in wooden areas –diatoms- to the ones in sunny areas –filamentous green-. Because of that, the amount of sun defines the amount of each type of algae to grow and the types of food available for fish and other aquatic organisms.

What happens when there is a nutrient excess in a water body..

Macroinvertebrates, small animals eaten by fish

Diatoms, algae eaten by macroinvertebrates. Grow in wooded areas

5. The stream riparian forest function as source of food and energy for different forms of life and also provides diverse and high quality wildlife habitat.

The many kinds of plants like grasses, shrubs, vines and trees grow in the riparian forests providing important habitats because they make available nesting areas for birds and other animals as well as a variety of food items for wildlife.

The unbroken riparian forest also provides a pathway called ecological or wildlife corridor, important for the movement and migration of animals. It works as a connection between isolated blocks of forests, important to keep a high bio and genetic diversity. Here is an interesting short article about wildlife corridors from the science and nature writer DeLene Beeland. Here is a 4 page article about wildlife corridors design.

Even the woody debris that falls into the stream has its’ importance since it provides cover for fish and invertebrates. The debris forms debris dams that form pools providing space, cover, protection from high flow and a diversity of microenvironments for fish and other aquatic life.

Debris dams also block the transport of sediment and smaller litter materials. Such delay in transport of organic material down stream allows sufficient time for aquatic organisms to utilize it. The slowing of transport helps protect the sudden deposition of sediments down stream. There are studies that have shown a link between the presence of large woody debris and habitat quality, population growth of fish, and a diversity of fish and other aquatic organisms. Since fish also have non-aquatic predators, their presence attracts other animals, again increasing the biodiversity.

Example of a woody debris dam

The woody debris, stems, leaves, buds, flowers, etc., that fall into the stream from riparian forest form the basis of the aquatic food chain. This organic material is broken down into small pieces by aquatic insect larvae, crayfish and other invertebrates; bacteria and fungi breaks these small pieces into very fine material known as detritus, used for food by many small aquatic animals that are food for bigger aquatic animals. It’s a very delicate balanced environment, everything is interconnected. If something happens on one end everything else is affected as well.

6. Riparian forest is important in stabilizing stream banks, reducing erosion, and providing high quality wildlife habitat.

As water passes through a riparian area, the roughness of the forest floor and the vegetation help reduce the energy of the water flow allowing some of the water to infiltrate into the ground to be stored in wetlands and reduce downstream flooding, reaching groundwater, and maintaining stream base flow during the summer months.

Storm water treatment options that integrate natural systems and bioretention areas, such as riparian forests, are less expensive to construct than storm drain systems and provide better environmental results. Here is a website that almost teaches you to make a bioretention system.

Riparian forests can save money by providing protection from floods and management of storm waters. Storm water treatment options that integrate natural systems and bio-retention areas, like riparian forests, are less expensive to construct than storm drain systems

* In the flood of 1993 in the Midwest, the forested floodplain areas had less damage to the levee system and river than grass or farmland areas. A savings of $50,000 to $250,000 per mile in property damage was calculated. Here you can learn more about the effects of the Midwest Flood on wetlands.

7. Riparian forests function as efficient sediment filtering systems that are environmentally sound and economically advantageous.

Sediment is carried to streams from sources such as cropland erosion, pasture erosion, range erosion, road and construction sites, and stream bank deterioration.

The problem is that sediment suspended in water can reduce the penetration of sunlight into the stream and affect the growth of aquatic plants;

Since sediment can make the water cloudy, aquatic organisms may have some difficulty to find food and fish can have their gills clogged or damaged;

When sediment gets deposited on the stream bottom it affects the bottom dwelling fish and insects and it also destroy fish spawning areas.

Large sediment deposits can fill in stream channels and increase the potential for flooding

Help reduce the amount of sediment reaching streams because sediment settles out when the speed of water flow is reduced as it enters the riparian forest due to contact with vegetation, decaying leaves, twigs, and branches. In addition to that, sediment is removed as water runoff and sediment infiltrate into and are incorporated into the porous forest floor. Mature riparian forests can reduce the sediment load of water flowing from upland crop fields by eighty percent.