In September this year, a piece of news from the World Conservation Union (IUCN) made everyone celebrate our country's national treasure - the giant panda was "downgraded" from endangered to vulnerable. People finally breathed a sigh of relief. We have achieved good results in protecting endangered wild animals.

However, scientists have found that the situation of bamboo forests in giant panda habitats is not optimistic. The area of ​​bamboo forests is reduced, the growth cycle of bamboo is shortened, and the quality of bamboo is reduced, which directly affects the survival of giant pandas. The strange thing is, why does a carnivorous bear like to be "vegetarian"?

Giant pandas should be the happiest and most dazzling animal stars on the earth. They are naive and often have fat bodies. It rolled around on the ground, and everyone gave it the cute nickname "Gungun". It's not something to be happy about for giant pandas to receive so much love and attention, because for "Gun Gun" this is a blessing in disguise.

The first census of giant pandas from 1974 to 1977 resulted in 2,459 giant pandas, but by the second census from 1985 to 1988, the number dropped sharply to 1,114. It can be seen that giant pandas originally lived a comfortable life in the forest, but they lost a large number of friends due to many reasons.

So, what is the reason why the number of giant pandas has plummeted and become an endangered species? Capture, killing, poaching, smuggling...or is it because it is too cute? These reasons are all threats It affects the survival of giant pandas, but the more important reason is that the bamboo forests that allow them to live and obtain food have been severely damaged.

Between 1950 and 1985, the number of large-scale forest industry enterprises in the three provinces of Shaanxi, Gansu and Sichuan increased to nearly dozens, excluding county-owned logging farms. The forest area logged was more than 400,000 hectares, and the average annual logging area was 2 With more than 10,000 hectares, the giant panda’s habitat area has plummeted.

Ouyang Zhiyun’s research group at the Ecological Environment Research Center of the Chinese Academy of Sciences analyzed the national events in the past 40 years in 1976, 1988, 2001 and 2013 by combining satellite remote sensing image data and ground surveys. Evolving characteristics of panda habitats. Ouyang Zhiyun said that from 1976 to 2001, the giant panda's habitat area decreased by 4.9%, and at the same time, the average patch size of the habitat decreased by 24%. In other words, the habitat area of ​​giant pandas has not only been reduced, but has also been severely fragmented. Dividing large populations of giant pandas into small populations is detrimental to the long-term development of pandas.

Chen Yiping, a researcher at the Institute of Earth Environment of the Chinese Academy of Sciences, said: "As the main food of giant pandas, the growth and development of bamboo are affected as CO2 rises, leading to early flowering, early death, and shortened life cycle. And the rejuvenation of bamboo requires a longer period of time. cycle. In addition, rising temperatures also extend the life cycle of bamboo armyworms and other pests, and the increase in insect pests affects the yield and quality of bamboo, thus threatening the survival of pandas."

Natural selection is a natural selection. According to the law, no species can exist on the earth forever. So, will giant pandas also face the crisis of reduced evolutionary potential?

Fortunately, the genetic diversity of giant pandas has not been affected by population changes. Effects of reduced numbers. In 2008, the "Giant Panda Genome" project was launched. Scientists sequenced the giant panda's genome. The results showed that the giant panda has 21 pairs of chromosomes, a genome size of 2.4Gb, a repetitive sequence content of 36%, and more than 20,000 genes. Although the number of giant pandas in the population has not exceeded 2,000, the giant panda genome still has a high heterozygosity rate, which infers that it has high genetic polymorphism.

In people’s minds, the low reproductive rate and high cub mortality rate of giant pandas are also the reasons for the negative growth pattern of this population. However, this is due to the lack of systematic understanding of the reproductive behavior of wild giant pandas. erroneous conclusions drawn. Research shows that the annual reproduction rate of wild giant pandas is as high as 65.4%. Therefore, the reduction of bamboo forests directly threatens the reproduction and expansion of the giant panda population.

Speaking of all this, I have to mention a question. The sharp decrease in forest area will also threaten the safety of many animals, but this may be a disaster for the giant panda. The important reason is that "Gun Gun" eats almost only bamboo. Why is this? This question is so profound that scientists are still unable to give a definite answer.

Is this a question of "chicken and egg" or "egg and chicken"? Is it because the ancestors of giant pandas first changed their diet and then changed their genes, or is it because they mutated their genes first and then led to their eating habits? Has anything changed?

First, let’s take a look at the “family tree” of giant pandas. The ancestor of the giant panda is Eo-panda, a panda that is larger than the current giant panda. Of course, it is not as cute as the current giant panda. The panda is a carnivore that lived in the late Miocene 8 million years ago. The main branch of the giant panda population continues to evolve in China. In the early Pleistocene, 3 million years ago, a small panda evolved. Its size is only half the size of the living panda. Its fossils are defined as a small species of giant panda. . It can be inferred from the teeth of the fossilized giant panda species that the giant pandas were already omnivores at that time. Later, with the extension of subtropical moist forests, giant pandas gradually increased in size. In the middle and late Pleistocene epoch, 500,000 to 700,000 years ago, the size of the giant pandas of that period, the Basin subspecies, was larger than that of the living giant pandas. are larger and rely on bamboo for their livelihood.

According to the research results of researcher Wei Fuwen of the Institute of Zoology, Chinese Academy of Sciences, in the long history of evolution, the giant panda population has shown two significant expansions and contractions, while the three existing genetic populations are composed of two Subpopulations are differentiated and formed. Combining China's paleogeological data, researchers believe that the two expansions and two contractions of the giant panda population are closely related to paleoclimate turbulence. The cold climate of the glacial period caused the giant panda population to shrink or even reach a bottleneck, and the warming climate of the interglacial period caused the giant panda to survive. Population expansion has provided favorable conditions, and human activities over the past three thousand years have been the main factor leading to recent population changes of giant pandas.