Which of the following statements is correct about the ecological environment in northern China?

Hengshan Mountain, Wutai Mountain and the northern section of Taihang Mountain in the northeast of Shanxi were once densely forested areas. For example, Song Yaohui's Draft describes "dense forests" and "pine forests everywhere" in the northern part of Taihang Mountain. Liang Qingshan Zhi described Wutai Mountain in the Song Dynasty as "surrounded by Mengqingshan Mountain in Lin Lei, with mountains and valleys ringing". Written in the Ming Dynasty, the Biography of Hu Gao's Prohibition of Cutting contains: "Since ancient times, the five peaks have stretched for more than 700 miles, with trees towering into the sky and birds not crossing, and the country is still at the beginning." In the Ming Dynasty, palaces were built in Beijing, and most of the timber was taken from Daizhou (Wutai, Daixian, Fan Shi and Yuanping), which caused serious deforestation. "Ming Jing Shi Wen Edited" recorded the scene of deforestation at that time: "Hundreds of households are neighbors, so we can't catch them, but we can't ban them." The forest area was burned to ashes and the number of loggers was swept away. Only one million big trees are sold to Beijing every year. In this way, the forests of Hengshan Mountain and Wutai Mountain were swept away.

The south-central part of Shanxi is much warmer than the northwest, and the trees are more lush. According to the record of Taiping Yuhuan in Song Dynasty, there are many cypress trees in Xishan, Taiyuan. In the Northern Song Dynasty, the east and west mountains of Taiyuan were still "clouds of Cooper, Sophora japonica and wood" and were called "Jinxiu Mountain". Yuan Haowen of the Jin Dynasty said in the book "Crossing Jinyang Old City" that the West Hill of Jinci was "like a screen lying in the water, three hundred miles gloomy". In ancient times, there were many records about forests in the south and southeast of Shanxi. Shan Hai Jing mentioned that Zhongtiao Mountain and Taihang Mountain are luxuriant in trees and rich in bamboo. The Book of Songs describes the southern section of Taihang Mountain as a "pine and cypress mountain." Yecheng (Linzhang, Hebei), the capital of the Eastern Wei Dynasty, built palaces and used Shangdang materials. Licheng and Pingshun areas are "densely forested and easy to obtain materials." "Meng Qian Bitan" contains: "Gradually to Taihang, Songtai Feng", and so on.

The above historical data fully show that the Loess Plateau is indeed a region with widely distributed forests in history. It's a pity that "grassland theorists on the Loess Plateau" completely ignored such a large number of vivid historical documents. Even leaving aside historical data, the reality of forest distribution in the Loess Plateau is enough to prove that it belongs to the forest grassland belt. Now, the plantations in the northernmost part of the Loess Plateau are thriving, which is proof. For example, in Youyu County, which was once buried by quicksand, more than 654.38+00,000 mu of artificial forests (Larix principis-rupprechtii, Pinus tabulaeformis, Populus simonii, etc.) were built. ), known as the "oasis". Another example is Hequ, Yulin and Jingbian, which were attacked by the front of the Mu Us Desert. Hundreds of thousands of acres of artificial forests have been built, with lush trees. The reason is that there is more than 400 mm precipitation in the local area, and its habitat conditions allow forests to grow. It is originally a forest and forest grassland environment, otherwise it is difficult for forests to survive into forests. Forests in the northern part of the Loess Plateau can still grow well, not to mention the central and southern parts.

Second, the causes of ecological environment destruction in the Loess Plateau

It can be clearly seen from the above that the Loess Plateau before Qin and Han Dynasties was a forest and forest grassland. However, due to man-made destruction for a long time, a large area of forests gradually disappeared and became today's barren hills. Large-scale destruction of forests includes war damage, palace building, logging, deforestation and land reclamation. Among them, deforestation is the most serious and thorough destruction of forests. In the past two thousand years, the ecological environment of the Loess Plateau has been destroyed by continuous logging and reclamation. Since Qin and Han Dynasties, the Loess Plateau has experienced three climaxes of deforestation and land reclamation. The first time was a large-scale "reclamation" (organized reclamation by border guards) and "immigration" reclamation in the Qin and Han Dynasties. This large-scale "reclamation" has caused large-scale destruction of forests in northern Shanxi and northern Shaanxi. The second time was a large-scale "reclamation" in the Ming Dynasty, which caused unprecedented havoc to the ecological environment in the northern part of the Loess Plateau. According to textual research, in the early Ming Dynasty, the system of "ploughing fields" was vigorously promoted in northern Shaanxi (Yan 'an, Suide and Yulin areas) and northern Shanxi on the Loess Plateau, and the task of destroying forests and reclaiming land was imposed on every border guard. The Records of Diseases in Counties and Counties in the World records that "the land near the soldiers and guards in the world is divided into villages" in the Ming Dynasty. As soldiers and civilians scrambled to cut mountains and hoe fields, hills and hills covered with forest and grass were turned into farmland, making wasteland "crisscross among thousands of mountains and connected with hills and mounds". According to Shi Wen's Compilation, on the way from Yongning (now Lishi) to Yan 'an (Sui 'de), "that is, the cliff of the mountain, no matter how big or small it is, it is not cultivated". From here, we can easily see that the system of "reclaiming wasteland" implemented in the Ming Dynasty caused serious damage to the environment. The third reclamation was in the Qing dynasty, and the system of rewarding reclamation was implemented. The scope of reclamation moved from northern Shaanxi and northern Shanxi to southern Inner Mongolia, and millions of acres of grassland in the northern Loess Plateau and Ordos Plateau were reclaimed as farmland, which made the land desertification and soil erosion intensified.

It should be pointed out that the system of extensive cultivation and thin harvest has prevailed in the Loess Plateau since ancient times, and the agricultural proverb is "Don't hit a hundred burdens". Instead of choosing land suitable for farming, they used intensive cultivation to increase food production. Instead, it adopts the rotation system, releases Yamakaji by hook or by crook, plunders and expands cultivated land, and produces food by relying on natural fertility without fertilization. After planting for several years, the topsoil is lost, and when the fertility is used up, it will be abandoned. Choose another slightly better wasteland for farming. In this way, all the land covered by forest and grass has been shaved off, and the original forest and grass vegetation provenance has been destroyed and cannot be restored due to long-term endless reclamation. It can be seen that the failure of extensive planting and crop rotation system are the main bane of the complete destruction of the ecological environment in the Loess Plateau and the main cause of environmental deterioration.

Third, the ecological disasters caused by the destruction of the ecological environment in the Loess Plateau.

Forests are the "guardians" of the environment. After a large area of forest in the Loess Plateau was destroyed, it lost its ecological barrier and the ecological environment deteriorated seriously, which led to a series of disastrous consequences, such as the depletion of river water sources, soil erosion, intensified sandstorms, and increasingly frequent droughts and floods. This is a serious historical lesson. There are five main ecological disasters that still plague the Loess Plateau: