Someone should invent plants that grow on concrete. These plants should like the concrete barriers of the highway. Not only would the optics be nicer, but the plants would suck in the carbon dioxide from the automobile exhaust and make cleaner air.
I googled around for plants that grow on concrete and came away with only one discrete hit. A Canadian company wanted to develop grass seed that would grow anywhere, so they made one that would grow on concrete without soil. Now this won't work because the seeds would blow away, unless you made a slurry of paper that dried and pasted the seeds to the concrete. However, when the slurries dry there isn't enough moisture to grow the seeds.
I thought about a lot of possibilities, like drought resistant algae or moss that would grow on the highway barriers. Clearly there needs to be some creative biology and plant breeding. Someone will eventually breed a plant that will grow on concrete.
There is another way to greenify the highways. That method is to re-design the concrete barriers such they they will grow grass. Take a look at this photo that I found of a plastic highway barrier:
It is plastic filled with sand. Suppose that it were hollow, made to collect rainwater, and had a surface matrix such that it would hold plant seeds, and let the rootlets through to the water, all at the same time of having a mechanically sound traffic barrier. That would be the ticket. Of course you would still have to develop drought-resistant, winter-resistant and salt-resistant plants for the millions of traffic barriers that already exist, but the new ones could make our highways and byways a lot greener. Inventors, get your thinking caps on.
I found the images for this blog entry at: