The spatiotemporal changes of marshland and the driving forces in the Sanjiang Plain, Northeast China from 1980 to 2016

Background:Wetland loss is a global concern due to its enormous ecosystem services.Marshland,a typical natural wetland,which is concentrated in the Sanjiang Plain,has undergone dramatic loss in the last several decades.The spatiotemporal changes in marshland were studied based on Landsat images of the Sanjiang Plain from 1980 to 2016 with the land use maps in 1980,1995,2000,2005,2010,and 2016 using land use dynamic degree and landscape indices.The driving forces of marshland loss,including biophysical factors,socio-economic factors,and land management,were analyzed with boosted regression trees(BRTs)methods.Results:The area of marshland loss was 7372 km^(2),which accounted for 65.7%of the area of marshland in 1980;however,the paddy field area was expanded by 22,313 km^(2).The lost marshland was mainly converted to dry farmland(47.5%)and paddy field(47.2%)during 1980-2016.Both the landscape pattern of the study area and marshland became increasingly fragmented.The relatively important factors responsible for marshland loss were biophysical factors,socio-economic factors,and land management,which accounted for 65.2%,25.5%,and 8.4%,respectively.The most important driving forces with high“relative influence”were“distance to river,”which accounted for 20.6%of the total variance explained.The“relative influence”of potential crop yield and ditch density reached 20.2%and 8.4%,respectively.Conclusion:Significant land use changes have occurred in the Sanjiang Plain over the past 37 years,with characteristics of rapid paddy field expansion and drastic marshland loss.Meanwhile,marshland fragmentation continued to increase.Reclamation was the main reason for the large-scale marshland loss.Biophysical factors influenced the decisions regarding the locations of marshland loss.Moreover,climate factors(i.e.,average annual precipitation and average annual temperature)also played an important role in marshland loss.These results can provide helpful knowledge for understanding the patterns and reasons for marshland loss and protecting and managing strategies for wetlands restoration.