Why is that an important difference? To capture wind and solar you have to build turbines and solar panels which aren't free. You also have to have batteries to store them because of seasonal nature of these sources. You also need to transmit the energy thousands of miles through electrical grid because these sources of energy are limited to certain areas. Building the electrical grid itself just needs cutting out millions of more trees. So overall, the environmental impact of going full solar/wind would be worse than a combination of solar, wind, nuclear, and even maybe natural gas.