Earth biosphere damaged by Gamma-ray bursts

Earth biosphere damaged by Gamma-ray bursts

Wild Card's progress: nominated

This Wild Card came from: 

The source of this Wild Card: 
"Gamma-Ray Bursts Could Halt Photosynthesis"

Likelihood timeframe and scenario features : 

Wild Card's description 
Gamma-ray bursts originating thousands of light-years away cause serious damage to the earth biosphere, including shutting down photosynthesis in the oceans at depths of up to 260 feet. Gamma-ray bursts are linked to mass extinctions on Earth in the far past. They carry energies equivalent to billions of nuclear bombs going off at once.