The Network Sustainability Mechanism is a Zcash protocol reserve that temporarily removes ZEC tokens from circulation and distributes them to miners as block rewards over decades.

From the articleZcash Grants Group Proposes Redirecting $124 Million in Funding to Mining Rewards; Industry Criticizes PlanAlso in Zcash grants committee offers $46M back as critics demand coinholder control - Cryptopolitan, Zcash Grants Group Offers $46M Amid Governance Backlash