SAPPORO, Japan (Reuters) - Climate change could cut South Africa's maize crop by 20 percent within 15 to 20 years as the west of the country dries out while the east is afflicted with increasingly severe storms, its environment minister said on Sunday.

"For a developing country that's major, and major bad news," Marthinus van Schalkwyk told reporters after arriving in northern Japan, where the Group of Eight rich nations' leaders are gathering for a summit this week.

"For us it's not something far in the future, it's already happening."