See also an earlier blogpost on remaining challenges to PES: such payments must be sufficient to change behaviour, and better measurement of ecosystems services are needed to ensure that transfers are cost-effective.
Local PES mechanisms are an important step, but need to be complemented by global mechanisms to support global goals. They are also one of many responses to conserve and restore the world's natural capital. Others are to address the misspecification of property rights, remove perverse incentives and improve the content and flow of information on the benefits and value of natural capital.
For more on mechanisms to restore natural capital see this recently released book by Aronson et al.
Africa still lags behind on well-functioning PES schemes according to this very recent study.