Abstract: The Malthus population principle, which believes the mass population must lead to the population pressure, and leads to the fragility of the ecosystem, has some fallacies. In fact, with the progress of society and the development of economy, the problem of hunger has been solved, and the bearing capacity of nature has been strengthened. With the increase of population, population pressure does not necessarily increase, but may decline. Therefore, the relationship between population capacity and environmental quality is not necessarily reverse. Inner Mongolia Autonomous Region, China is situated between 37°24′-53°23′ N and 97°12′-126°04′E, with a total area of 1.183 million square kilometers. The terrain slopes from northeast to southwest in a narrow and long shape. In recent years, with the degradation of meadow and farmland caused by overgrazing and cultivation, the relationship between human and land has become more and more tension in desertification areas, which shows a trend of excessive pressure on the utilization of natural resources and environmental carrying capacity. Desertification is an important problem in the sustainable development of ecological environment and social economy in northern China. There are many research results on this problem, but there are few innovations in the study of the causes of desertification. Referenced the principle of Malthus population, this paper constructed a model from the root of desertification and a model from the causes of desertification which took the population pressure into the research innovatively based on the county panel data of Inner Mongolia Autonomous Region. This paper analyzed the quantitative relationship between population pressure and the development and reversal of desertification, and investigated the mechanism of population pressure on the development and change of desertification areas in 68 desertification counties (banners) from 1990 to 2010.In this paper, the population pressure was divided into grain pressure and enrichment pressure, and 68 counties in Inner Mongolia were divided into eastern, central and western regions, and two virtual variables were introduced. Based on them, we investigated the difference of the effect of population pressure on desertification in different regions. It is found that within the range of observed data, population pressure is closely related to the development and change of local desertification. Before 2000, the population pressure increased continuously, which significantly promoted the expansion of desertification. Since 2000, the population pressure has been continuously reduced through regional transfer, and the desertification in this area has been effectively alleviated. The study also showed that the effect of population pressure on desertification in Inner Mongolia Autonomous Region shows obvious temporal and spatial differences. Through the research, we think that the population pressure is the main cause of desertification. The last part of the paper puts forward some suggestions on how to jump out of the Malthus trap at present. In this paper, the theory of population pressure is applied to the field of desertification research, and the internal force is detected to explain the causes and changes of desertification, which could provide a new perspective for the future research on desertification.

Key words: population pressure, Malthus trap, desertification, virtual land, Schultz human capital