The reason of "Loulan is dead"

Statement 1: Loulan disappeared in the war. After the fifth century, the kingdom of Loulan began to weaken, and the northern powers invaded, and Loulan City was destroyed and then abandoned.

Statement 2: Loulan was defeated by drought and water shortage, and the ecology deteriorated. After the upstream river was cut off, people had to leave Loulan. Loulan promulgated the world's earliest environmental protection law discovered so far.

Statement 3: The disappearance of Loulan is related to the north-south migration of Lop Nur. Sven Hedin thinks that the period of north-south migration of Lop Nur is about 1500 years. More than 3,000 years ago, there lived a European ethnic tribe in Loulan area. Loulan once again entered a prosperous era more than 1500 years ago, which was directly related to the wandering of Lop Nur.

Statement 4: The disappearance of Loulan is related to the opening of the North Road of the Silk Road. After the opening of the Silk Road North Road through Hami (Yiwu) and Turpan, the Silk Road Desert Road through Loulan was abandoned, and Loulan lost its former glory.

Statement 5: Loulan was destroyed by the plague. A plague from other places claimed the lives of nine of the ten residents in Loulan City. Those who survived by luck fled Loulan and fled other places.

Statement 6: Loulan was defeated by biological invasion. An insect introduced from the two river basins has no natural enemies in Loulan, lives in the soil, can live in the albic soil in Loulan area, and enters the houses in droves. People can't destroy them and have to give up the city.