Depletion of stratospheric ozone increases the amount of ultraviolet-B (UV-B) irradiation experienced on Earth. Now Ries et al. report in the 6 July Nature that increased UV-B exposure can reduce the genomic stability of plants (Nature 2000, 406:98-101). They use a reporter gene inserted as a tandem or inverted repeat as a probe to detect 1.7-fold to 14-fold increases in homologous recombination after increasing UV-B levels. The plant germline is protected from UV-B for much of its life, and yet the higher levels of UV-B also cause a 4-10-fold increase in germline recombination.