Synopsis: Increased CO2 improves environment for plant life; CO2 'greens' the world.
Source here. "A 300-ppm increase in the air’s CO2 content typically raises the productivity of most herbaceous plants by about one-third; and this positive response occurs in plants that utilize all three of the major biochemical pathways (C3, C4, CAM) of photosynthesis. For woody plants, the response is even greater. The productivity benefits of CO2 enrichment are also experienced by aquatic plants, including freshwater algae and macrophytes, and marine microalgae and macroalgae."