Ecosystems are a community of where living plants, animals, bacteria (i.e. biotic) interact and rely on non-living things like water, nutrients, rocks, energy (i.e. abiotic). Since ecosystems can virtually be any size (small like a pond, to virtually the entire world), here we are focusing on freshwater ecosystems. Further, in discussing ecosystems, we will also focus on the habitat, where the freshwater biotic organisms receive the necessary food, water, and energy needed to survive.
Ecosystems function through food webs – where smaller organisms and animals are consumed by larger or better suited predators. As such, ecosystems thrive off of habitat diversity, where greater specie numbers provide greater stability. As we have discussed on Our Water pages, water pollution, reduction of physical processes in rivers, poor watershed management, and inefficient water infrastructure has been responsible for degrading the quantity and quality of water available in freshwater ecosystems. Therefore, all the solutions presented on these pages are relevant; however, here we present specific habitat benefits.
To reduce water pollution, we mainly focus our attention to reducing the amount of water pollution from city and agricultural runoff, industrial waste, and temperature and suspended matter. These improvements will:
- enable greater diversity and quantity of freshwater species. Over last 4 decades, fresh water species have decline by 76% (World Wildlife Fund), and improving water quality would provide a major step forward in replenishing these numbers.
- increase bacteria and bugs in freshwater will have greater ability to process nutrients
- reduce sediment and suspended matter, which will
- improve habitat conditions (since this can clog fish gills) and keep fine sediment limited, which can bury spawning areas for fish and habitat for bacteria and bugs
- and allow light to penetrate deeper into the water depths, thus allowing aquatic vegetation to thrive. This increase in aquatic vegetation will provide more food and shelter for bugs and fish and greater ability for the ecosystem to absorb nutrients.
- reduce temperature spikes that often make species leave or die, and in more mild temperature differences it can make species not reproduce.
Overall, improving the water quality will drastically improve the diversity and numbers of freshwater species. As new research suggests, healthier river systems (ones with abundant bugs, fish, and plants), naturally absorb and process pollution better than degraded systems. Therefore, improving the water quality will have sort term and long term gains to the ecosystem and provide cleaner and safer water for humans.
The physical processes of a river (hydraulics, morphology, and vegetation) are what helps a river maintain biological and physical vitality. Through everyday low-flows, and infrequent flood events (i.e. hydraulics), rivers naturally evolve through erosion and deposition (i.e. morphology changes) and in these processes nutrients are delivered to biota, and habitats are destroyed and re-created. The following improvments will benefit ecosystems:
- Allowing/designing dams to:
- release/pass sediment will maintain a connected river process and provide downstream habitats the constant supply of nutrient delivery from finer sediments.
- release/pass regular flows to ensure that maintain the minium water necessary for a healthy ecosystem functionality.
- release flood events that will help downstream systems generate new habitats through sediment and vegetation disturbances.
- incorporate fish passage to allow the natural cycle of spawning and migration.
- Vegetation management will ensure that the right species are thriving, and the invasive species are minimised. This will ensure that the proper balanced ecosystem is functioning.
- Finally, in the case of floodplain development, expanding the available room for the river to evolve will not only create new habitat, but it will expand the available and valuable habitat.
Watershed protection plans are vitally important to healthy ecosystems, particularly the vast miles of freshwater ecosystems in the smaller headwaters. These areas are typically smaller water volumes and limited populations, but they have the majority of river miles and land use (i.e. farming and forestry), making them some of the most susceptible to ecosystem degradation. Effective watershed management can have the following ecosystem benefits:
- Improving dam planning and design can accomplish both the need for water storage, but proper design and watershed consideration can locate new dams in areas of least impact. By limiting dams to tributaries, and not main stems of rivers, dams can have significantly less impact on the entire ecosystem by allowing the majority of sediment transport, fish passage, and less modified river flows.
- By working with agriculture, forestry, and mines (abandoned or active), watershed protection efforts can help identify land water drainage can significantly help reduce the amount of pollution and fine sediment from entering the freshwater ecosystems. Further, through planning, action, and some funding, riparian buffers, crop borders, and native crops during the winter can significantly improve the land's ability to reduce the amount of pollution/sediment runoff as well as improve the infiltration of surface water, which would lead to improved ground water storage. All of these improvements would drastically improve the water quality and thus the habitats and environment.
- Through reforestation and wetland restoration, these watershed improvements will help process pollutants, increase the water storage, and in some cases may help influences the local climate by reducing land, water, and air temperature and promoting precipitation. Through greater water storage, the land will act like a sponge - soaking up water when it is dry, and slowly releasing it when it is wet. This ability will help a steady water supply to the ecosystem.
- Restoring natural landscapes and indigenous vegetation along along rivers is vastly important for ecosystems functioning.
- Smaller herbaceous vegetation provides food and shelter for both aqueous and land biota and also helps rivers function properly through flood events and natural evolution of morphology.
- Larger vegetation, like trees, offer two main benefits. First, the trees' shade helps regulate water temperatures. Second, all organic material that eventually falls in to the river (leaves and dead trees), will provide food and shelter for the biota. Particularly, large woody debris research shows that "more than 75 percent of wood structures placed in rivers and streams remain in place and provide habitat benefits for a decade or more." While relatively few studies of restoration projects monitor fish numbers, "studies of the monitored projects reported significant increases in the frequency and depth of pools and improvements in habitat complexity and spawning gravels following the placement of instream wood structures" and of the "81 studies that examined the response of fish to wood structures, 68 reported a positive response in fish abundance, biomass or survival for at least one fish species and life stage." (NOAA). Further, large wood in rivers helps the creation and maintenance of bar formation and vegetation establishment, which can ultimately lead to bifurcation and increased floodplain connectivity, and thus making river channels more habitable for many species (especially young juvenile fish) as well as providing better feeding grounds for predators.
Due to old and outdated infrastructure piping, a significant portion of the water drawn from rivers, lakes, and dams never even makes it to the fields. In fact, up to 1,500 trillion liters of water are lost annually due to old agriculture irrigation infrastructure (WWF). Possibly worse, household leaks go undetected through toilets and leaky faucets, which when scaled to every household can be an enormous amount of water. Just in the United States, it is estimated that 1 trillion gallons are wasted due to common household leaks (EPA).
All of this waste would have been very valuable if left in the ecosystem. Simply having more water will increase the depth, width, and physical processes of any body of water.
Depth: While many freshwater systems are governed to maintain minimal water levels for species survival, deeper pools have been shown to drastically help fish abundance and survival. This is due to added habitat area, increased security of deeper pools, and simply a bigger area to maintain the ecosystem diversity.
Width: The added expansion of the water will not only provide more room for the freshwater species, but will add valuable area of food and shelter. In general, the bigger and more diverse the system is allowed to be, the interactions it will have with ecosystem biota, and return help pull pollutants and provide clean water.
Volume: The added volume of water will help dilute any pollutants that enter the system. With less and less water available, the introduction to pollutants will becomes significantly more potent and dangerous. Further, increasing the water volume of any system will help promote added physical processes, where the water's flow can interact with sediment and vegetation, and ultimately help provide the necessary processes that help maintain a healthy and dynamic ecosystem.
- "Freshwater species declined 76% between 1970 and 2010" (World Wildlife Fund)
- More than 50% of wetlands in parts of North America, Europe, Australia, and New Zealand were destroyed during the twentieth century (Millennium Ecosystem Assessment)
- Some wetlands have been found to reduce the concentration of nitrate by more than 80%. (Millennium Ecosystem Assessment)
- More than 20 percent of the 10,000 known freshwater fish species have become extinct or imperiled in recent decades. (National Geographic)