According to a scientific analysis at the end of 2019, there are at least tens of millions of animal species on Earth. Insect experts also specifically pointed out that there may be 5.5 million species of insects alone. For centuries, biologists, ecologists, and taxonomists have documented biological species on a global scale. Andy Purvis, a biodiversity researcher at the National Museum of History in London, said: “It’s hard to know how many species have been recorded, let alone the difficult challenge of counting how many unknown species there are in the world.” It is difficult for scientists to have an accurate statistics on the number of species on the earth. The difficulty is mainly reflected in the following three aspects:
First, the earth is full of biodiversity and has a complete independent ecosystem. It is difficult to explore it at the current technological level. At the same time, there are still many species that live in unknown fields on the planet and have not yet been discovered. Scientists have recently discovered a “lost world” in the mountain jungle of Indonesia, and found many new species of birds, butterflies, frogs and plants there; on the island of New Guinea in the South Pacific, scientists have discovered An inaccessible rain forest mountainous area where hundreds of species that have never been discovered by humans grow, as well as hundreds of thousands of rare frogs, insects and plants.
Second, as McKean, an ecologist at the University of Florida, emphasized, even in areas we are familiar with, there are many undiscovered species, or there are still some known species that are difficult to count because of their large numbers. In 2019, he participated in the “National Biodiversity Championships” held in the Greater Louisville area of Kentucky, USA. A total of about 200 people participated in the four-day competition. They discovered 760 species, many of which have almost no records, and some species appeared for the first time in Kentucky. In this regard, McKean sighed: “In the United States, we are surrounded by biological diversity, which makes our best scientists feel small.”
American biologist John Wiens discovered through research that almost every insect may carry at least one mite. Mites are small arthropods that live on the surface and gaps of insect bodies. For example, some mites live exclusively on the antennae of marching ants. More importantly, there are also small bugs in the stomachs of insects called “nematodes”. Therefore, when the number of specific nematodes and mites growing on a specific insect species is counted, the number of potential species in the world will increase explosively. In this regard, McKean said: “What we know now is that many species are structural species.” Simply put, it is a type of species that provides habitat for other species.
Third, the difficulty of counting biological species lies in the fact that there are still many “mysterious” species in the world that are difficult to classify. The entomologist Randall Schoch of the American Museum of Natural History said: “When we walk into nature and see individual organisms, they cannot be distinguished at all, because they have no name on them, nor can they tell us that they themselves What kind of animal are there. Some species seem to be widely distributed and in large numbers, but in fact, they may be a group formed by multiple hidden species.” Hidden species refer to the same genus, their morphology is very similar, only It is difficult to distinguish based on surface characteristics. At present, the number of known hidden species is mostly small, or even on the verge of extinction. In addition, scientists do not know how many unknown hidden species in the world, so there is no way to protect the hidden species.
Therefore, the biggest challenge facing scientists is not to count how many species there may be on the planet, but more importantly to understand as early as possible how many of these known species are threatened or endangered by human activities. At present, the culprits that endanger the global flora and fauna are destroyed wilderness, accelerated climate change and extensive pollution. Now, about 70% of the ice-free land on the earth is affected by human activities, which means that the habitat of wild animals is inevitably reduced. According to the report of the United Nations, the rate of extinction of modern species has reached the highest value in human history, which is tens to hundreds of times higher than the normal rate of extinction in the past 10 million years. In modern history, not only are little-known species extinct, the report also emphasizes that the number of large vertebrates has declined sharply since the 16th century, and more than 100 species have disappeared almost every century, with at least 680 species today. Vertebrates are extinct due to human activities. The rise in extinction is an important reason for humans to find new species-“Before they disappear forever, it is best to move quickly.” McKean believes.
At present, taxonomists have mastered some new research techniques, especially the DNA sequencing technology of “mysterious species” and small species. This DNA sequencing technology is helping scientists to obtain genome maps of more and more unknown species. Biologists are also involved in a series of research projects that find biological lineages by classification, such as the “Census of Marine Life” and the “Planet Biodiversity Directory” dedicated to bed bug research led by Schuker. As McKean said: “The debate about how many species there are is eternal.”
