<em>Abstract</em>.—The Yangtze River is the largest river in China, with a drainage area encompassing a land area of 1.8 × 10<sup>6</sup> km<sup>2</sup>. The river main stem flows approximately 6,300 km from west to east through 11 provinces, eventually emptying into the East China Sea. The total basin area of the Yangtze River provides more than 40% of China’s gross domestic product, sustains nearly 500 million people, and plays a vital role in the overall socioeconomic development of China. Because of longitudinal differences in geomorphology, the Yangtze River is often divided into upper, middle, and lower reaches for the purposes of study and description. In general, the Yangtze River basin has a warm climate and abundant rainfall. The subtropical monsoon climate accounts for 70–80% of its annual rainfall, which produces predictable annual flood events during summers of each year. The Yangtze River ecosystem also has diverse aquatic habitats that support high biodiversity. The Yangtze River main stem contains more than 3,000 tributaries and approximately 4,000 lakes that provide important habitats for thousands of aquatic species, which include 378 fish species. Yet, the ecological communities of the Yangtze River have been dramatically impacted in recent decades due to high degrees of anthropogenic activities associated with the economic development of China. Significant biodiversity declines occurring throughout the basin have been largely attributed to hydropower dam construction, overexploitation of major fisheries, water pollution, and habitat fragmentation. In addition, widespread disconnection of the Yangtze River main stem from its floodplain lakes, lake reclamation projects, invasions by exotic species, and other serious ecological problems threaten the survival of the remaining aquatic resources in the basin. To offset the adverse effects of these threats, a number of nature reserves have been established. Additionally, protection and restoration measures, including spring fishing closures, artificial population enhancement strategies, and complete habitat restoration projects, have been implemented throughout the basin. Although these projects have yielded some encouraging results to date, they are still considered inadequate. It is recommended that an integrated strategy that includes cross-functional communication mechanisms, more comprehensive monitoring, ecological rehabilitation, and government legislation is still needed. This will insure that utilization and development in the Yangtze River ecosystem are sustainable and balanced with conservation and ecological needs.
Evaluation of airborne image data and LIDAR main stem data for monitoring physical resources within the Colorado River ecosystem