Producer: Popular Science China
Production: Zhou Yangyang (Little Elephant Jun AnimalDialogue)
Producer: Computer Network Information Center, Chinese Academy of Sciences
After the snow melted last winter, I put a bird feeder in front of the window and installed a mixture of seeds specially formulated for wild birds, including peanuts and melon seeds, and dried cranberries. The surrounding birds soon discovered the treasure, and different birds came to eat it every day.
I put a whiteboard in front of my desk to remember the bird species I saw. Because of the pandemic, I've been at my desk longer than before, and the list of birds has been long. From the beginning, I didn't know any birds, but slowly I could distinguish between the white-bellied lantern grass bunting, the North American cardinal, the black-hated, the hairy-crowned, and even the personality was clear. North American cardinals like to stand there sniffing melon seeds, and the crowned blue jay cries every time, steals two peanuts and runs away. The furry-crowned are the cutest, and even when I'm standing not far away, they come generously to eat them, and after taking one grain, they have to give it to their other half (this is the first time that they have been sprinkled with dog food by birds).
△ South American toucan
Birds are perhaps the animals that give us the most intuitive appreciation of biodiversity. These elves, though not easily approached, are the easiest animals to hear and one of the closest "natures" to us in an increasingly urbanized world.
More than 10,000 kinds of birds in the world actually have their own beauty, from the gorgeous feathers, to the shape of the beak, to the sound of singing, we can not help but marvel at the magic of biodiversity. Darwin, the father of evolution, found that by observing local birds on the Galapagos Islands, although these birds obviously look very similar and share a common ancestor, their beak shapes are very different. Fruit-eating birds have thicker beaks, while slender beaks usually belong to insect-eating birds, so Darwin concluded that "these birds originally had the same ancestor, but due to the scarcity of resources during evolution, different birds chose different foods and evolved corresponding beaks, becoming different species."
△ A kingfisher
In the era when Darwin wrote On the Origin of Species, the definition of "species" mainly relied on the naked eye of the researcher to distinguish the appearance of animals, plus some understanding of animal habits. However, according to Darwin's explanation of how "species" appears, it is easy to have such a question: a species has changed in appearance because of the evolution of adapting to the environment, but to what extent is this species considered a new species? How should the boundaries be drawn between closely related species?
Textbooks now basically define species as "species that are naturally capable of mating and producing fertile offspring, reproductively isolated from other species." Such an explanation is easy to understand, and it is easy for researchers to define and quantify. Quantification is important in data-based scientific research, because in this way we can define "the sum of all species" as a noun – "biodiversity." "If you count the species in an area and add it up, you can see if the species in that place are "diverse." This statement is simple and clear, so at the beginning of the century, scientists represented by Norman Myers proposed to divide the world's land according to the number of species, find out the "biodiversity hotspots" with the most species in the world, and use limited money to protect the most species in the case of establishing protected areas with limited areas.
△ A small red-headed kingfisher
However, when we really want to take action to apply this concept of biodiversity to practical operation, this definition shows great problems.
<h1 class="pgc-h-arrow-right" > question one: "Is "species" really the smallest unit of protection? </h1>
It is not known how well Darwin spoke to the shape of the bird's beak, because the song of the bird is a tool that distinguishes the species of bird more than the shape. In the same region, similar-looking bird species can accurately find their own kind by discerning the song of their own race, avoiding mating with distant cousins who "look like".
However, the dark green willow warbler in the Himalayan region has broken the boundaries of species - these species originally came from the same area on the west side of the mountain, and gradually spread to the distribution around the Himalayas, but every time they are farther away from the place of origin, the song of these birds' populations changes a little, so that the dark green willow warblers that go around the north side of the mountain reach the east side of the mountain, and the dark green willow warblers who come around the south side of the mountain are dumbfounded after meeting - although they come from the same ancestor, their songs have become completely different. Can't mate with each other anymore. Paradoxically, if you walk back in the "footsteps" of their population spread, you will find that in any two adjacent areas, the "song" of the dark green willow warbler is slightly different, but they can still recognize each other as the same kind and mate to give birth to offspring. Such a "ring species" inevitably makes taxonomists scratch their heads: the two groups of dark green willow warblers that cannot mate on the east side of the mountain should be counted as one species or two species? If we ask a more realistic question, we only have enough money to protect a small area, so which group should we protect? Should these "transitional populations", which are constantly undergoing subtle changes from the northern side of the mountain, also be protected?
△ A raccoon
This dilemma occurs in the protection of the Tatra mountain ibex (Capra ibex) in the Czech Republic. In order to protect these goats, which were extinct in Czechoslovakia, the government imported a small number of goats of the same kind from Austria. Alpine sheep from Austria survived in the same climatic conditions, but Austria did not want to give more goats, so they imported goats from Turkey. However, Turkish populations are accustomed to a drier, warmer climate, and the offspring they produce after mating with the local populations in autumn rather than winter, resulting in the possibility of the young sheep being born after the coldest February, and eventually the Czechoslovak flocks were not able to avoid extinction. These flocks belong to the same "species" at every level, but in order to ensure their survival in an ecosystem, it is clear that the definition of this "species" alone is no longer enough to meet our needs, and the term "subspecies" has gradually spread widely.
With the popularization of gene sequencing technology, it has been found that more and more animals that were previously considered to be the same "species" actually have very different genes, such as people once thought that the golden jackal was widely distributed in Eurasia and the African continent, but from the latest genetic testing, the African "golden jackal" is actually closer to the wolf. Species that were previously thought to be unable to mate have also been shown to have a constant flow of genes, such as the gray wolf and coyote wolf in North America, which overlapped habitats due to the excessive occupation of land by humans, resulting in the otherwise unrelated gray wolf and coyote wolf mating with each other and giving birth to offspring. Similar "hybridizations" occur in many endangered species.
△ A proboscis raccoon
<h1 class="pgc-h-arrow-right" > question two: Can quantity represent everything? </h1>
The world's ecosystems are diverse, and if we were to divide by species, as the Myers call them, we would only get a "biodiversity hotspot" that surrounds the Earth's equator. After all, what could be more species than a rainforest? Marine ecosystems are simply ignored, because plant species alone can produce much more on land than in the ocean.
However, beneath the seemingly boring surface of the seawater is actually another complete ecosystem. At the bottom of the sea, there are not only mountains and canyons on land, but also "volcanoes". Where the plates meet the plates, the mantle under the ground is constantly emerging from the depths of the ground because it is hotter and lighter. The cold sea water above flows down the gap, the cold sea water encounters the hot mantle, it evaporates, and the cooled mantle becomes rock, and the evaporated water carries the stones containing minerals, which have to overflow from the gap due to the increase in pressure, becoming a hot island in the cold seabed. According to measurements, the temperature of these hydrothermal vents can reach an average of 380 degrees Celsius.
△ Author's favorite western scrub jay (West Bush Crow)
Since the hot steam touches the seawater and cools quickly, the hydrogen sulfide precipitated from the metal is highly toxic. How can an environment with strong high pressure, no light, high temperature, and surrounded by sulfide survive? But there is such a group of creatures, thriving on the only source of heat in this cold deep sea. There's a giant tube worm ( Riftia pachyptila ) that is the star of the ecosystem of deep-sea hot springs. Although the name is not very honorable, these two-meter-long bugs, which have no mouth, no digestive organs, cling firmly to the surface of the rocks on the seabed, look more like clusters of red-haired enoki mushrooms. The red "hair" on the top of their heads is actually the gills used to capture oxygen, carbon dioxide and sulfides in the water, and then they will transport the captured inorganic matter to the bacteria in the body, which will convert these inorganic matter into organic matter, and the insects will use these organic matter to survive. In addition to giant tube worms, there are also many crabs and shellfish that rely on these bacteria to transform organic matter to live on the heat island on the seafloor.
Even if you don't find such a combination of organisms in any other ecological environment, even if you do, there is no egg use - from the perspective of biodiversity, an ecosystem with only a few organisms and some bacteria is really not "diverse" or "protective." "Without a basis for protection, these ecosystems become objects of exploitation. The abundance of sulphides and minerals on the seabed is favored by some countries with scarce terrestrial resources and abundant marine resources, and has become the object of their research and exploitation. In Japan and Australia, research on deep-sea mining has been ongoing, and we don't know what impact such mining will have on these giant tube worms and their partners. What is more dangerous is that once such ecosystems are destroyed, due to the harsh conditions of "going to the sea", the cost of repairing them may be several times or dozens of times that of terrestrial ecosystems.
<h1 class="pgc-h-arrow-right" > question three: How to protect species that are far away from us? </h1>
This problem has nothing to do with the creatures themselves, but it has to do with people's hearts - people are more willing to protect what they are familiar with, and these tropical rainforests and deep-sea hot springs, although they are desirable, are distant things from us, and if they are used as synonymous with biodiversity, it is inevitable that they will not be grounded and difficult to have a sense of reality. In fact, the animals around us are enough for us to appreciate biodiversity. When you are in the city, you can start to learn, listen carefully to the birdsong in the morning, and try to distinguish the different birds. When you see a bug you've never seen before, don't be busy screaming, distinguish its pattern and size, and you'll be surprised to find that nature that you thought was far away from the city was actually around.
Rachel Carlson, who used birds as the title of her famous book Silent Spring — Silent Spring, referring to the spring when birds can't be heard — painted a powerful stroke in the history of biodiversity conservation. In the era when DDT was used in large quantities as an insecticide, she proposed that a large number of birds were dying because of the toxicity of DDT, and eventually Americans who could not bear the death of beautiful birds around them amended the law to prohibit the use of DDT. Another example is the sadder, the American passenger pigeon. The book says they are so numerous that when the passenger pigeons fly into the sky, they can cover the sky. The extinction of this bird made everyone realize that numbers were not a guarantee of the survival of the race. In either case, these species are not in the distant rainforest, but can actually be seen and heard.
The radius of the Earth is about 6,000 kilometers, and the biosphere ranges from the deepest seabed to the highest altitude, but only 20 kilometers, and most of these organisms live between 500 meters below sea level and 6 kilometers above sea level. Therefore, some people say that if the earth is compared to an apple, the biosphere is nothing more than a layer of skin on the apple. However, this layer of apple peel is home to 10 million extant species, including humans. The charm of biodiversity may lie not only in its beauty and diversity, but also in its fragility, in its reach, and in how it is shaped by the influence of our every move.
The pictures in this article are all taken by the author, during the shooting, no animals were injured and wild animals were released into the wild, except for the cat.
bibliography:
1.Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G., & Worm, B. (2011). How many species are there on Earth and in the ocean?. PLoS biology, 9(8), e1001127. https://doi.org/10.1371/journal.pbio.1001127
2.Meyers N, Mittermeier RA, Mittermeier CG, da Donseca GAB, Kent J. 2000.“ Biodiversity hotspot for conservation priorities.” Nature