A new report from the U.S. Conference of Mayors says 4.2 million Americans will have green industry jobs by 2038… a dramatic increase from the current 750,000 green jobs in the country now.

“This report proves that being green is not optional, it is necessary for a healthy and robust economy,” said U.S. Conference of Mayors President Miami Mayor Manny Diaz. “Creating green jobs is an investment we must continue to make.”

Under assumed scenarios and with government commitment and investments, the report projects Green Jobs could contribute 10% of new jobs through 2038, representing the fastest growing job segment in the U.S. economy. By 2038, the report forecasts that renewable electricity production will create 1.23 million jobs; alternative transportation fuels 1.5 million jobs; engineering, legal, research and consulting positions will be more than 1.4 million; and commercial and residential retrofits at 81,000 jobs, for a total of 4.2 million.

The report assumes that 40 percent of the country’s electricity will come from alternative sources, such as wind, solar and biomass, 30 percent of gas and diesel for the nations vehicles will come from renewables, and homes and businesses will reduce their energy use by 35 percent by 2038.

The report was released during a Forum on the Environment and Energy held in Miami.