Severe droughts that happen once every 20 years will affect New Zealand once every two to five years by the year 2100 and the country's Pacific neighbors will need help to deal with the impacts of climate change, a leading New Zealand climate scientist warned Wednesday.

Auckland University climate scientist Dr Jim Salinger said the drought that affected New Zealand in the last southern summer, causing major difficulties for the country's pillar agriculture sector, would be much more common, as summers and winters became warmer.

"Flash flooding in our towns will be much more common with more high intensity deluges. And those with beach front hideaways will be more prone to attacks of storm surges and king tides from the sea eating away at their properties," Salinger said in a statement.

"We're unlikely to be shielded from the impacts of the global economic effects of climate change, caused by food shortages and general upheaval, and we could see many of our Pacific Island neighbors knocking on our door for help," he said.

"All tropical islands in the Pacific are likely to regularly experience heat waves of unprecedented magnitude and duration. Extreme heat waves in recent years have had severe impacts, causing heat-related deaths, forest fires and harvest losses."

Food supplies would be challenged with falling crop yields likely, especially in India, Africa, United States and Australia, by as much as 30 percent for wheat.

The New Zealand Treasury has estimated that the summer drought, which affected most of the North Island and parts of the South Island, could help shave up to 1 percent off the country's annual GDP growth.