Traditional inhabitants of the Loess Plateau

(1) The traditional houses in the Loess Plateau are caves; Coal is an important energy mineral in the Loess Plateau. Cities A and B in the picture are Taiyuan and Xi 'an respectively.

(2) With the population growth, the per capita arable land decreases and the fuel demand increases, people will expand the wasteland reclamation area, destroy vegetation, reclaim wasteland and cut down forests, resulting in a decline in crop yield;

(3) The information in Figure B shows that the ecological environment in the Loess Plateau is deteriorating and natural disasters occur frequently. The most prominent eco-environmental problem in the Loess Plateau is soil erosion. The causes of this eco-environmental problem are loose soil, heavy rain in summer, serious vegetation destruction and so on. To improve the ecological environment of the Loess Plateau, the reasonable suggestion is to plant trees and grass.

So the answer is:

(1) caves; Coal; Taiyuan; Xi an;

(2)③; ①; ④; ②;

(3) soil erosion; Loose soil, heavy rain in summer, serious damage to vegetation, etc. Planting trees and grass.