Current bottlenecks and prospects of the land use intensity

There are, in general, two aspects of land use, which is the most direct human activity on terrestrial ecosystems: land-use type and land-use intensity. However, studies on land-use intensity, which lacks the adoption of established concept models, indicator systems, as well as unified method frameworks, significantly fall behind those on land-use type. With the increasing intensity of human disturbance in the terrestrial ecosystem, the concept of land-use intensity is, once again, garnering significant attention. Studies on land-use intensity can be summarized into three branches: 1) Those concerned with the estimation of human activity intensity based on population density; 2) those in which traditional methods of input and output intensity, the multiple crop index, τ-factor method, the technical efficiency method, etc. are used; 3) those in which the conceptual model of land-use intensity based on social-economic circulation mechanisms of materials and energy, represented by the HANPP index, is used. Combined with studies on the driving mechanism of land-use intensity, research trends on land-use intensity reveal that 1) the population density, which used to be taken as an indicator of land-use intensity, is gradually being replaced by the conceptual models of land-use intensity; 2) land-use intensity studies are shifting from indicator constructs to the distinction between human and natural factors, which is one of the key challenges associated with index comparisons between different natural environments; 3) remote sensing data and methods have immense potential in the study of the quantitative recognition of human activities; 4) the assessment mechanisms for land-use intensity are closely related to agricultural land and the utilization and protection mechanisms for grassland and forest ecosystems are not valued. The balanced development of the assessment mechanisms of land-use intensity and index technology systems is expected to become the inevitable future trends in land-use intensity studies.The most direct human activity on terrestrial ecosystem-land use-generally cover two aspects: land use type and land use intensity. However, the development of researches on land use intensity, which lacks mature concept model, indicator system, as well as the unified methods framework, seriously fall behind the researches on land use type. As human intensifying disturbance in the terrestrial ecosystem, the attentions of scientists to the concept of land use intensity were again aroused. The evolution of the study on the land use intensity could be summarized into three branches: 1) studies on human activity intensity calculations based on the population density; 2) land use intensity researches represented by traditional method of input and output intensity, and the multiple crop index, τ-factor method, the technical efficiency method, etc. 3) the conceptual model of land use intensity based on social-economic circulation mechanism of material and energy, represented by the HANPP index. Combined with researches on driving mechanism of land use intensity, the research trends on land use intensity shows that 1) the population density taken as an indicator of land use intensity is gradually replaced by the conceptual model of land use intensity; 2) the land use intensity researches incline from indicators constructs to the distinction between the human and natural factors, which is the key problems of index comparison between different natural environment; 3) remote sensing data and methods have huge potential in the study of quantitative recognition of human activities; 4) the assessment mechanism for land use intensity were closely related to the agricultural land, the utilization and protection mechanism for the grassland and forest ecosystems were not valued. Balanced development of assessment mechanism of land use intensity and index technology system become the inevitable trends in the future research of land use intensity.