The currencies of commodity-exporting nations surged as a gauge of raw materials prices extended its longest rally in two years. The Australian dollar climbed for a sixth day while its Canadian counterpart rose for a third session and the South African rand and Mexican peso also rose. The currencies were bolstered by crude oil’s rally and strengthening industrial metals prices. “The fact that oil’s been able to hold now, and add to its recent gains almost on a daily basis, is driving a lot of that improvement in risk appetite,” said Omer Esiner, chief market analyst at currency brokerage Commonwealth Foreign Exchange Inc. in Washington. “That’s being reflected in a lot of the emerging-market currencies and a lot of the commodity currencies—that, on balance, is hurting the dollar.” The currencies of some nations that sell raw materials have started to react as prices for their exports turn up. They plunged in 2015 on concern that Chinese economic growth is slowing, damping the outlook for demand from world’s the second-largest economy. The Aussie gained 0.4 percent to 74.69 U.S. cents as of 5 p.m. in New York, the longest winning streak since October. The Canadian currency rose 0.3 percent to C$1.3282 per U.S. dollar, reaching the strongest level since November. The New Zealand dollar bucked the trend, declining after Fonterra Cooperative Group Ltd. lowered its milksolids forecast price. Oil Gains Brent crude surged more than 5 percent to exceed $40 a barrel for the first time since December as major producers prepared to meet to discuss a production freeze and U.S. output finally showed signs of declining. The oil rally also helped to prop up 14 of 24 emerging-market currencies against the dollar. The currency gains for resource-selling nations may be short-lived as market volatility returns, BNP Paribas said. “We remain inclined to fade gains in commodity bloc currencies versus the U.S. dollar,” Steven Saywell, the bank’s global head of foreign exchange strategy London, said in a note.