Recently from the third university of Toulouse, France? ET？ Diversit？ China Academy of Sciences (IHB), Institute of Aquatic Biology (EDB), Institute of Biology, and French Montpellier Marin Biological University. Exploitation? And then what? Conservation (MARBEC) Research Center and Marseille? A joint research team composed of INRAE(RECOVER) laboratory put forward a new biodiversity change index which comprehensively considered six biodiversity dimensions, and made a comprehensive evaluation on human beings.
The results show that more than half of the fish biodiversity in rivers is seriously affected by human activities, and the related results are published in the top international academic magazine Science.
Why is the Yangtze River closed to fishing for ten years?
Image source: Science
Rivers on the earth are rich in fish biodiversity. Up to now, 17000 species of fish have been recorded, accounting for a quarter of all vertebrates on the earth.
Will human activities affect the life of fish? We can all answer this question.
But how big is its impact? Can you answer this question?
How big is the impact of human activities on fish and how to evaluate it?
In the past, the research on fish biodiversity mainly focused on the temporal and spatial distribution changes of fish species and quantity, that is, whether the species and quantity of fish in river water increased or decreased after human influence.
However, with the deepening of ecosystem research and new changes in methods, more and more studies show that the diversity of a single species cannot reflect the differences between species.
Different fish have different functions in the ecosystem, and communities play different roles in the evolution process. For example, some small carp eat algae to inhibit the growth of algae in water, but if mackerel invades, they will eat small carp. Few fish eat algae, which promotes the growth of birds.
(1) food chain diagram of largemouth bass, small carp and benthic algae (2) From left to right, largemouth bass. There is no big mouth in the environment, and the growth of birds is inhibited. In the environment, largemouth bass promotes the growth of birds.
In recent years, the research method of 3354 based on fish functionality has gradually developed. Considering the characteristics of fish morphology, physiology, behavior and life history, the functions of different fish in the ecosystem have been well quantified. For example, in the early stage, the research group studied the main morphological indexes of 10 fish (body length, kidney rate, size and position of mouth, eyes and fins, etc.). ), the results show that even like freshwater fish, they are different. Moreover, there are obvious regional differences, and the morphological characteristics can show many main functions such as diet and swimming ability.
The map of morphological diversity of freshwater fish in the world is also very different from different species of freshwater fish | Image source: 3 references.
The research team put forward a new biodiversity change index CCBF (cumulative? Change? In biodiversity? Facet).
Species richness (the number of species in a single community), functional richness (the size of functional space), phylogenetic richness (the length of phylogenetic branches), species difference (the difference of species composition between communities), functional difference (the degree of functional space overlap between communities) and phylogenetic difference (the overlap of phylogenetic branches between communities).
Calculation framework of comprehensive change index CCBF of biodiversity
The research team simply synthesized the change rate of a single diversity index in six different dimensions, and got the comprehensive change index CCBF, which can be used not only to evaluate the change of freshwater fish diversity, but also to be widely used in many biota.
Therefore, CCBF computing framework provides an estimation model for other biota and ecosystems, which can quantify the impact of human beings on global biodiversity.
Based on this model, the research team investigated more than 2,000 rivers around the world and analyzed the data of more than 10000 fish on all continents except deserts and polar regions.
More than half of the fish in 2456 rivers around the world are seriously hindered by human beings.
Studies show that more than 50% of fish are strongly affected by human activities, and only 14% of the river basin is slightly affected. There are about 3876 species of fish living in rivers undisturbed by human beings, accounting for only 22% of the fresh water meat species in the world. This means that there is an urgent need to protect the biodiversity of rivers that have been affected by human activities.
During the research, the team found that it is easy to see three kinds of invasive fish, such as carp, cod and tilapia, in the clear water environment such as the reservoir formed by the dam.
More studies show that the success of fish invasion is related to morphological characteristics. These exotic species are often far away from local species, with larger body length and shorter body extension length, which are more suitable for this clear water environment.
Not only that, in general, the species, functions and phylogenetic richness of fish have increased significantly in most river basins invaded by alien species. Isn't it a good thing that the richness of fish communities in the environment has increased and the diversity of fish has increased?
It's not that simple. The invasion of alien species is not only to increase the fish richness of rivers. On the other hand, exotic species have put some pressure on local fish, resulting in a decrease in the number of local fish and may become endangered or endangered species. On the other hand, the widespread spread of these alien species between different river basins has also led to the phenomenon of biological homogenization in the environment, and the differences in species, functions and systematic development between fish communities in disturbed rivers have weakened, that is, the community structure and functions in the water environment have become more and more similar.
Research shows that more than 70 species of fish recorded in the world1are completely extinct, and 23% of the fish's living conditions are threatened. Therefore, on a larger global or regional spatial scale or long-term time scale, the increase of fish population at this stage is not a good phenomenon.
Because once the invasion is successful, it is difficult to eradicate, and species extinction is an irreversible ecological disaster.
Engineering construction, water pollution. In some ways, human beings have similar influence and pressure on most river basins in the world. Due to human interference, fish that can adapt to the pressure of human activities can continue to survive, while the number of fish that cannot adapt to the pressure of human activities may be reduced or even extinct.
The species and functions of fish in rivers will become more and more similar. When the world changes greatly, the freshwater ecosystem will be more easily destroyed.
If necessary protective measures are not taken, the extinction of endangered fish will lead to a drastic change in biodiversity and endanger the basic services provided by aquatic ecosystems to human beings.
Happily, China has taken the lead. After the Yangtze River banned fishing for ten years, dolphins frequently appeared in Wuhan section of the Yangtze River, and the number, frequency and duration were rare in recent ten years.
But this is really just the beginning. I believe that the implementation of this plan can greatly improve the living conditions of fish and other aquatic organisms in the Yangtze River basin.
However, the situation in other parts of the earth is very serious.
Especially in Europe, America, Australia and other industrialized areas, the CCBF values of most rivers are close to the extreme value 12. At the same time, in South America, where the biodiversity of freshwater fish is the richest in the world, only 6% of rivers are almost unaffected by human beings.
Man and nature complement each other, which is not only a slogan, but also a guide to action. Humans need to do more. John F. Kennedy