Climate Determines Marsh Ecological Asset in Zoige Pastoral Area over the Past 40 Years

In recent years, there has been an increase in the quantity of marsh ecological asset (MEA) on the Qinghai-Tibetan Plateau due to climatic warming and humidification. However, the alterations in the quality of the MEA in this region remain unclear. Here, we constructed a marsh quality index (MQI) based on the structural (including marsh fractal dimension, FD; and river network density, RN) and functional (including river runoff, Rr; and Normalized Difference Vegetation Index, NDVI) indices of marshes to assess the change in the quality of MEA between 1980 and 2020 in the pastoral areas of Zoige County. We also examined changes in MEA quantity. And the relationships between the MEA and environmental variables were tested using grey relational analysis. We found that the quantity of MEA experienced an increase of 564.41 km2 from 1980 to 2020 in the pastoral areas of Zoige County. This rise was mainly due to the conversion of grassland into marsh. The MQI results demonstrated that there was a steady improvement in the quality of MEA, which was mainly attributed to the increase in RN, Rr, and NDVI. While the quantity and quality of MEA showed a strong association with climatic factors, their correlation with livestock numbers was found to be weak. These findings suggest that changes in MEA are strongly controlled by climate change and thus nature-based approaches should be highlighted for the conservation and management of MEA in plateau regions.