Nuclear activists point out that reactors do not generate greenhouse gasses and that decommissioning them leads to electricity being generated by fossil fuels (some nuclear opponents claim that reactor technology is polluting; I looked into this several years ago and was not impressed by the quality of the research).
Renewable-energy supporters claim that sufficient wind energy is being installed each year to offset the loss of reactors (averaging about one decommissioning per year ). Surprisingly output from reactors has remained steady. Improved efficiency must be the reason, since there have not been any new reactors for many years .
Generation by renewables have strongly increased from about half of nuclear in 2008 to about two thirds today. Since hydropower has remained steady, the increase is due to wind.
So far so good. Since nuclear production has been steady, wind has helped to take up the slack due to coal plant retirement.
 EIA, Today in Energy, June 13, 2017
 Data in the figure from EIA, Electricity Data Browse, accessed July 1, 2017