The main enemies of freshwater are hydropower, poaching, hazardous waste and global climate change.

Fresh water is perceived by people for granted, therefore, care for its preservation fades into the background.

Freshwater bodies are actually fewer,than the oceans and seas combined: only 3% of the earth's water does not have a high salt content. From this minority depends on the life of the billionth population of the planet, growing against the background of the remaining amount of water. It does not become more or less, but not only the quantity is important.

The quality of fresh water should not disturb peopleless than its flaw. According to the Organization for the Conservation of Nature, more than half of the world's 500 major rivers are already polluted. Water from these tanks could be a resource for millions of people, but due to the level of waste it cannot be used.

One sixth of the world's population has no directaccess to water, and the US Agency for International Development predicts that by 2025 the situation will worsen: water will be available to only one-third of humanity. This is the future catastrophe of all mankind, but the cataclysm for other forms of life has already begun. 17.4 thousand species live in different types of freshwater reservoirs, and for them the quality of water is no less important than people.

The paradox of diversity: most aquatic organisms live in fresh water. The volume of oceans, while almost 1000 times greater than the volume of rivers and freshwater lakes. If to describe in numbers - 50.7% of aquatic organisms live in 0.009% of water.

Cretaceous biocenotic crisis of living diversityorganisms began about 135 million years ago and ended with the extinction of dinosaurs. This was the last major period of extinction of living organisms on Earth, and the new did not happen until our days. Some researchers believe that the next such crisis will begin in the anthropocene era due to global climate change and people in particular. It’s early to make pessimistic forecasts, but scientists have reason to be alarmed.

Colorful bland world: a variety of species

The biodiversity fund is made up oforganisms living in all types of freshwater bodies. The classification of reservoirs divides them into rivers, lakes, ponds, small ponds and artificial reservoirs. The type of water varies depending on whether it stagnates in water bodies or constantly flows from one place to another.

The inhabitants of the reservoirs are also divided into severalgroups. These are periphythons, benthos, nekton, plankton and neustons. Periphytes parasitize the dead and living inhabitants of the bottom, finding shelter in the mud or among the algae. Actively floating and mostly large creatures - nektons, including most fish, amphibians and insects. Representatives of the benthos live in the depths: worms, mollusks, and some fish like gudgeon, sterlet, and burbot, who prefer the lower layers of freshwater bodies of water. Plankton, unable to resist the flow, drift in the water, and the neustons gliding along the smooth surface are water striders, smooth-bed bugs and wriggle beetles.

Bioindication - assessment of human impact on the reservoirthe reaction of its inhabitants to the external environment. Bioindicators are the inhabitants of the studied reservoirs, replacing each other, depending on water quality. In polluted water bodies, for example, leeches and prudoviki live, while in pure waters they are replaced by vislokrylki and mayflies.

The presence of leeches in reservoirs indicates the degree of contamination. Leeches live in polluted water bodies. In the net, they are replaced by visokrylki and polenki.

Not all reservoirs are tested, but about the statewater can be judged by external signs: flowering, water color and its viscosity. Another good indicator is endangered species and dead fish. Over the past decade, more than 20% of the ten thousand known species of freshwater fish have either become extinct or are on the verge of extinction. Marguerite Xenopoulos, a biologist from Trent University in Ontario, says: "The numbers are an alarm bell, and we urgently need to take measures to preserve freshwater ecosystems."

The global index of a living planet is formed from data on vertebrate populations and population dynamics. The fluids for freshwater populations have decreased by 81% since 1970: danger levels are measurable.

A study published in the journal ScientificReports, reports the gradual disappearance of the European river mollusk. This representative of bivalves lives about 200 years and lives in fresh rivers of Europe. Environmentalists noted a sharp decline in shell populations in their habitat. In order to investigate the causes of extinction, scientists collected samples from fifty European rivers, and also studied specimens of shells from natural science museums — collections were collected as early as the 19th century. The reason for reducing the population was trivial, but no less dramatic.

Global Warming and Intrusive People

Factors changing freshwater ecosystemsinterrelated and reduced to the essence of the anthropocene. Without human exposure, the rate of extinction of organisms might not be as fast. Nevertheless, today the inhabitants of rivers and lakes are forced to adapt to the gradual increase in water temperature and the constant change in its chemical composition.

In the case of the European mollusk criticalturned out to be an increase in ambient temperature. This type is characterized by a geographic change in the ratio of width to length — convexity. Scientists have discovered that earlier this indicator was the same for all mollusks, southern and northern. Today the situation is this: the colder the water in the river, the smaller the bulge on the sink. The cold beginning of the 20th century was much more comfortable than the current trend towards global warming. Warm water accelerates the metabolism and growth of shells, so the mortality of larvae and juveniles reduces the overall life of the population.

Warming changes not only mollusks, but also the environmenttheir habitats. In the rivers there are more algae, they often overflow the banks. Pessimistic forecasts predict the extinction of European mollusks. Pearl oysters can survive only in high-mountain icy rivers, where the temperature remains the same.

The second reason for the gradual extinctionfreshwater organisms - anthropogenic impact, and in particular, the results of industrialization. The exploitation of water resources of rivers and lakes by industrial enterprises leads to large-scale pollution of nearby waters. Although technology reduces waste, new wastewater treatment plants are being introduced on a minority of enterprises. The annual use of approximately 30 billion cubic meters of water at the outlet gives 700 million cubic meters of wastewater. The disintegration of chemical wastes in water takes years, during which substances penetrate groundwater and spread to nearby bodies of water.

Harm is brought not only by industrial waste. The cheapest way to produce electricity is hydropower. It is a source of renewable energy, taking the resource from rain and snow. Engineers easily control volumes of distilled water, and reservoirs are not only of strategic, but also of public importance - these are good options for winter skating rinks or artificial reservoirs.

Dams and hydrostation bring not only benefitsbut also detrimental to nature. An artificial change in the flow of rivers, the retention or acceleration of water leads to a change in the direction of movement of the fish. Salmon, for example, swims to spawn upstream through fish ladders, but dams or power plants can be a serious obstacle that literally prohibits breeding.

Fish ladder - specialized water facilities, divers of different height from 50 to 500 meters. These rapids provide natural migration of fish up and down the river.

The BioSciences study showed thatHydroelectric power plants reduce oxygen levels: the amount of methane and carbon dioxide in the water increases. Fish do not always successfully adapt to temperature increases, and, in addition, suffocate from lack of oxygen.

Oksana Nikitina, Project Coordinatorto the conservation of aquatic ecosystems of WWF Russia, commented on the massive construction of facilities that use the energy of rivers: “Aquatic inhabitants are evolutionarily adapted to the natural dynamics of the water regime, which determines the time of their reproduction, migration and feeding. Violation of the mode leads to failure of life cycles. If the river is not isolated from the surrounding area by dams and dams and preserves the natural water regime, it is called freely flowing. The construction of dams led to a sharp decrease in the number of free flowing rivers: more than 50,000 large dams have already been built in the world. ”

Another “human” threat is poaching. Non-normalized fishing of fish and other inhabitants of freshwater bodies destroys ecosystems. The quota for catching is usually set by the federal authorities: when calculating, the season, the number of populations, and the tendency to increase or decrease are taken into account. For example, in one year from a reservoir it is possible to catch six trout and only three in the following. Of course, poachers catches rarely meet the established standards.

How to cope with the crisis of freshwater?

Today, scientists are developing an understanding of the functionseach element of the biosystem of each individual reservoir. So far, the definition of the role of any organism that lives in a particular lake is complicated by the uniqueness of environmental conditions. Unlike large saline bodies of water, the particular cases of lake and river ecosystems may differ significantly from each other. The only thing that remains the same is the importance of living in water. Because of this, techniques for saving species are effective point-to-point, but not on the scale of all freshwater bodies of water. The situation requires a change in external, not internal conditions.

The crisis of freshwater diversity will not end inovernight, but this does not mean that you can give up and stop the acute stage. Now people can limit the construction of dams, create more protected freshwater areas and reduce industrial and personal water intake. By the way, anyone can find out how much water he spends every day - you need to use a special calculator.

Enterprises may collect special pumps forpumping runoff waste. They allow you to clean the channel from sediment with the help of dredging buckets and roiling jets. Settings are created for each reservoir separately: take into account the nature of bottom sediments, hydraulic resistance of the channel, erosion factors.

It is especially important to reduce the number of builtthe dams. “To preserve aquatic ecosystems, it is important to initially protect particularly valuable parts of river basins from the possible construction of dams. It is necessary to prevent the construction of those dams that are designed without due regard for their impact on ecosystems. If construction is still unavoidable, then we should choose those dams, the location of which has the least impact on the environment compared to other options, ”adds Oksana Nikitina.

Freshwater is not a secondary concern.humanity, but an important component of the overall ecological balance. A man in the street who is aware of the importance of preserving freshwater bodies should follow the necessary minimum recommendations for protecting the environment and preserving water resources. Banal tips: save water, sort garbage, relax in specialized places - not an empty phrase, but the real basis for saving the planet.