Synthesis and Outlook

This chapter reflects on the most important results presented and their relevance and implications for wetland management and restoration. Overviewing the contents, there are two general areas where this volume will break new ground. The first is the more rigorous underpinning of the two most important regulating wetland ecosystem services, and the second is the presentation and critical discussion of the strong, recent activities in wetland conservation and restoration in China and neighboring countries. The two regulating wetland ecosystem services meant here are (1) the capacity of restored and constructed wetlands to remove nitrogen and phosphorus from through-flowing water and (2) the role of wetlands in cooling or warming the climate as the net balance between carbon sequestration and emissions of methane and nitrous oxide. It is a robust fact that wetlands can be expected to remove 40% of the nitrogen and phosphorus from runoff and groundwater flow in agricultural areas. The area of wetland needed to really make a difference at the catchment level amounts to 10% of the total catchment area. With respect to the cooling/warming function of wetlands, there is now firm evidence that newly originating wetlands start off as having a net warming effect on the climate, because the warming effect of methane emissions surpasses the cooling effects of CO2 sequestration and evapotranspiration. In the course of time, the cooling function will increase due to the persistent cooling of already sequestered carbon. This re-emphasizes the enormous importance of “old” wetlands such as peatlands over newly formed ones in the climate regulation service. On the other hand, climate change effects will enhance the overall primary productivity and carbon sequestration in herbaceous coastal as well as inland wetlands. Increasingly, sea level rise and warming will result in more opportunities for forested wetlands (mangroves, boreal forest), which will enhance the climate cooling service of wetlands worldwide. The book also contains a number of chapters reflecting the large investment in ecological research in wetlands in China and neighboring countries in recent decades. There are chapters on the effects of invasive species on coastal wetlands, on the protection and wise use of coastal wetlands around the Yellow Sea, and on the principles and recent case studies of wetland restoration in this part of the world. The ecosystem services of wetlands definitely play a major role in the motivation and justification of large projects for wetland restoration. The results of these projects so far are most promising.