What this study makes abundantly clear is that ecosystem services
provide an important portion of the total contribution to human
welfare on this planet. We must begin to give the natural capital
stock that produces these services adequate weight in the decisionmaking
process, otherwise current and continued future human
welfare may drastically suffer. We estimate in this study that the
annual value of these services is US$16–54 trillion, with an
estimated average of US$33 trillion. The real value is almost
certainly much larger, even at the current margin. US$33 trillion
is 1.8 times the current global GNP. One way to look at this
comparison is that if one were to try to replace the services of
ecosystems at the current margin, one would need to increase global
GNP by at least US$33 trillion, partly to cover services already
captured in existing GNP and partly to cover services that are not
currently captured in GNP. This impossible task would lead to no
increase in welfare because we would only be replacing existing
services, and it ignores the fact that many ecosystem services are
literally irreplaceable.