Drastic land pattern change has taken place in the northeast region of China, which may have a significant impact on landscape and ecosystem service. Up to now, insufficient renewal of land use patterns may limit the latest assessment of landscape transition and ecosystem service value. Meanwhile, the adaptive ecosystem service value improvement method should be established. To solve this issue, the integrated methodology of land-use change monitoring—landscape analysis—the promoted ecosystem service measurement is established. Results show that: (1) New evidence is observed that the cultivated land in Northeast China has been reduced, with 309,610.33 km2 in 2010 and 309,417.52 km2 in 2020, showing a net change area of −192.82 km2. This is the opposite of the increase of cultivated land compared to the past. (2) Shannon’s diversity index displays an upward trend, with the richer landscape types and higher fragmentation in the whole region. In addition, the contagion index reduced, with a total decrease of 1.93, indicating that the patches distribute intermittently and the agglomeration degree of these patches is weakened. (3) More precise ecosystem service value is assessed, from 2868.39 billion yuan in 2000 to 2814.06 billion yuan in 2020, and the hydrological regulation, climate regulation, and soil conservation play a dominant role in these functions in 2020. The spatial pattern of ecosystem service value is high-rank in the Northwest and Southeast, and low-rank in other directions. This study provides the new results on land change and landscape pattern and creates an improved ecosystem service value assessment method in Northeast China, to provide a more suitable ecosystem assessment application for Northeast China.

Large-scale and high-speed paddy land expansion has appeared in Northeast China since the 21st century, causing the change in land surface temperature. The lack of continuous investigation limits the exploration of discoveries in this region. To address this limitation, a collaborative approach that combined human–computer interaction technology, gravity center model and spatial analysis was established. It provided some new findings in spatiotemporal evolution, migration trajectory and surface cooling effect of the paddy field in Northeastern Sanjiang Plain, a center of paddy field planting in China. The results show that: (1) A sustained paddy expansion was monitored, with a total area ranging from 2564.58 km2 to 11430.94 km2, along with a rate of growth of 345.72% from 2000 to 2020. Correspondingly, its reclamation rate changed to 47.53% from 10.66%, showing the improved planting level of the paddy field. (2) Gravity center of paddy field continued to be revealed northward with a 5-year interval from 2000 to 2020. Migration distance of the straight line reached 23.94 km2, with the direction offset of 27.20° from east to north. (3) Throughout the growing season of crops, the land surface temperature of paddy field was 27.73°, 29.38°, 27.01°, 25.62° and 22.97° from May to October; and the cooling temperature effect of paddy field was investigated, with the reduced values of 0.61°, 0.79° and 1.10° in the low-, medium- and high-paddy field density regions from 2000 to 2020, respectively. Overall, these new findings in the cold temperate zone, high latitude region of the Northern Hemisphere, provided the reference for the investigation of paddy field monitoring and its environmental effects in China and other regions.