After reaching an all-time high in 2010, this year the nuclear power capacity—the amount of electricity that all the world’s nuclear power plants can produce—took a dip.

(Related: World Electricity Mix Interactive)

The earthquake-tsunami disaster at the Fukushima power plants in Japan, which are still being cleaned up, led many to sour on nuclear energy. Soon afterward, Germany and Switzerland decided to completely phase out their nuclear plants within a few decades, and some of Germany’s oldest nuclear plants were shut down indefinitely. All together, 13 nuclear plants shut down in the first 10 months of 2011, according to a new report by the Worldwatch Institute. Construction of new nukes also slowed, with 16 plants getting started in 2010, but only two this year—one in India and one in Pakistan.

(Related Photos: “The Nuclear Cleanup Struggle at Fukushima“)

“It’s too early to conclude that nuclear energy is beginning a long-term decline, but these numbers can hardly encourage the industry,” Robert Engelman of Worldwatch said in a release that highlighted the nuclear power plant numbers.

“The high cost of nuclear electricity generation and the widespread public perceptions that it poses unacceptable safety risks make it unlikely this form of power will help slow human-caused climate change or offer an attractive alternative to rising fossil-fuel prices any time soon,” Engelman argued.

(Related: “Japan, Germany Struggle With Nuclear Power Slowdown” )

However, the International Energy Agency, which released its annual World Energy Outlook last month, disagrees. The IEA expects nuclear power to keep growing, but the recent report included a chapter covering what might happen if the world gradually shifted away from nuclear power, so that the nuclear power capacity dwindled from today’s level.

“Such a slowdown in the growth of nuclear power would make it more challenging for emerging economies, particularly China and India, to satisfy their rapidly growing electricity demand,” the report said. And for the world to limit warming to 3.6 degrees Fahrenheit (2 degrees Celsius) above the pre-industrial temperature, this “low nuclear” scenario would require “heroic achievements in the deployment of emerging low-carbon technologies.”

Far more renewable energy is exactly what the Worldwatch Institute would like to see, pointing to high rates of growth of wind and solar in recent years. But there are signs these high rates of growth may soon slow down. Renewables are facing a tough situation in the U.S. and globally, solar power installations in 2012 may also fall—the first such drop in the modern history of the industry.