You mean just engineering? Oh sure. We might even build giant vertical farming things for some crops. But spread out just a little more like to Australia size, then ya got a population density like South Korea, which means you could have ordinary farming also. Really, the problem with the human population isn't so much the how, as the tragic side of our non-cooperation: the "Tragedy of the Commons" writ large.
Tragedy of the commons - Wikipedia
In other words it wouldn't be hard to support a much larger population without harming the environment, but it would take a truly different social economic organization in some key ways (which could still allow freedom, enterprise, etc.). Musing to myself: Isn't classic Georgism actually a possible solution, if fully implemented?
Georgism - Wikipedia
So, I think between things like some bridging regulation and global Georgism, we could change and save the environment easily I think -- not would not even be a huge, radical change.
Just some key things, like all nations agree to participate in the common re regulation/allocation rights of special use of the air, oceans, natural resources -- example: CO2 emitting tax, global, proceeds rebated to all nations.
Then, we could have a bigger population without destroying the environment. But not under our current system. Under our current system, we aren't doing it, and will destroy the environment.