The decade-long surge in foreign-currency reserves held by the world’s central banks is coming to an end.

Global reserves declined to $11.6 trillion in March from a record $12.03 trillion in August 2014, halting a five-fold increase that began in 2004, according to data compiled by Bloomberg. While the drop may be overstated because the strengthening dollar reduced the value of other reserve currencies such as the euro, it still underlines a shift after central banks — with most of them located in developing nations like China and Russia — added an average $824 billion to reserves each year over the past decade.

Beyond being emblematic of the dollar’s return to its role as the world’s undisputed dominant currency, the drop in reserves has several potential implications for global markets. It could make it harder for emerging-market countries to boost their money supply and shore up faltering economic growth; it could add to declines in the euro; and it could damp demand for U.S. Treasury bonds.

“It’s a big challenge for emerging markets,” Stephen Jen, a former International Monetary Fund economist who’s co-founder of SLJ Macro Partners LLP in London, said by phone. They “now need more stimulus. The seed has been sowed for future volatility,” he said.

Stripping out the effect from foreign-exchange fluctuations, Credit Suisse Group AG estimates that developing countries, which hold about two-thirds of global reserves, spent a net $54 billion of this stash in the fourth quarter, the most since the global financial crisis in 2008.

China, the world’s largest reserve holder, together with commodity producers contributed to most of the declines, as central banks sold dollars to offset capital outflows and shore up their currencies. A Bloomberg gauge of emerging-market currencies has lost 15 percent against the dollar over the past year.