Sustainable use of a natural resource ensures that the ecosystem associated with that use will also provide long term environmental services to society.  Such services might include the provision of clean water, removal of excess CO2 from the atmosphere, flood protection, pleasant vistas, or enhanced biodiversity.  These benefits are becoming less abundant as inappropriate resource uses hasten environmental degradation.  
In theory, if beneficiaries pay for the environmental services received, and these payments are given to the resource users/owners to reward, or encourage, sustainable resource use, then such sustainable use will be assured.  Schemes to implement such arrangements might be able to support conservation programs, and also supplement income of poor farmers and forest dwellers.  Such payments are also seen as a means of encouraging better management of carbon dioxide in our atmosphere, by paying for forest practices which can store CO2.  
How do such systems actually work?  Can payments for environmental services encourage better resource management?  Might they also create disincentives for management based on ethics, altruism, and stewardship?  A generic system dynamics model was used to examine these questions.