Since the 1970s, some regions have introduced the cultivation of European and American black poplars for papermaking. These European and American black poplars adapt to the local climate and environment, grow rapidly, and the area of planting has expanded rapidly. However, in recent years, local ecological and environmental problems have become increasingly serious. It is believed that the ecological environment in the region can be repaired by cutting off these European and American black poplars. Which of the following options best point out the shortcomings of the above discussion? ['Assume that other crops can replace the economic value of European and American black poplar.', 'Ignoring other exotic plants introduced in the area can also affect the ecological environment.', 'It is assumed that the planting area of European and American black poplar introduced in this area is much larger than the area of local tree species.', 'The causal relationship between the expansion of the poplar planting area in Europe and the United States and the ecological and environmental problems.']