  Wetland quality is a critical factor in determining values of wetland goods
and services. However, in many studies on wetland valuation, wetland quality
has been ignored. While those studies might give useful information to the
local people for decision-making, their lack of wetland quality information may
lead to the difficulty in integrating wetland quality into a cross-studies
research like meta-analysis. In a meta-analysis, a statistical regression
function needs withdrawing from those individual studies for analysis and
prediction. This research introduces the wetland quality factor, a critical but
frequently missed factor, into a meta-analysis and simultaneously considers
other influential factors, such as study method, socio-economic state and other
wetland site characteristics, as well. Thus, a more accurate and valid
meta-regression function is expected. Due to no obvious quality information in
primary studies, we extract two kinds of wetland states from the study context
as relative but globally consistent quality measurement to use in the analysis,
as the first step to explore the effect of wetland quality on values of
ecosystem services.
