Interference from human activities and changes in natural factors work together to co-affect wetland ecosystems, but the different rates of their contributions to wetland ecosystems still lack adequate research. This research studied variations of the types, distributions, and spatial patterns of wetlands over 28 years, from 1987 to 2015, in the water catchment area of Napahai watershed, Northwestern Yunnan plateau, based on the methods of object-oriented segmentation and visual interpretation. The study also explored the interrelationships between wetland variations and human activities (i.e., socio-economic development indicators) together with natural factors (i.e., climatic factors). The results showed that (1) the total wetland area was reduced by 2456.46 hm², out of which the primary swamp, swamp meadows, and meadows were reduced by 1152.07, 1257.72, and 202.74 hm², respectively, and lake area increased by 156.07 hm². (2) The diversity of wetland landscapes changed over the years. Specifically, the number of patches (NP) increased from 221 in 1987 to 299 in 2005, and then decreased to 260 in 2015; the Shannon diversity index (SHDI) increased from 1.81 in 1987 to 1.84 in 1999, and then decreased to 1.75 in 2015; the contagion index decreased from 52.82 in 1987 to 52.02 in 1999, and then increased to 53.49 in 2015. (3) Wetland distribution area and SHDI were negatively correlated with the three industry values and mean annual temperature, and they were positively correlated with mean annual precipitation. However, unlike wetland distribution area and SHDI, NP and contagion index exhibited positive correlations with the three industry values but negative correlations with mean annual precipitation. (4) The main socio-economic development index contributed 63.50% of the variations in the wetland area and landscape diversity index, while climatic factors contributed 36.5%. Overall, the study showed that disturbance by human activity is the critical driving force for shrinking wetlands and landscape diversity changes. Thus, mitigating the excessive impact of human activities on wetland ecosystems is the key to protect the resources and maintain the functions of wetland ecosystems.