Tons of greenhouse growers intentionally boost the C02 levels up to 1000 or 1200ppm.

Growth will be limited by water, soil nutrients, sunlight or CO2. When there's enough of the other 3, increasing CO2 will increase growth (and deplete soil nutrients more rapidly). If you've got a greenhouse in a sunny area, and you're going through a lot of fertilizer, you will have more production. The economics would be more against if you were paid for nutritional value and not weight.

It won't help most farmers as much, as soil fertility is the most common limiting factor in an agricultural situation.

It just seems like hubris to me to say 350ppm is the be all end all answer forever, and that we must control the atmosphere at all costs to maintain this C02 level.

If we lose 80% or 90% of the planet's biodiversity we lose a huge resource too.

But technology certainly will help agriculture. It's the low tech farmers of Africa and South East Asia who will starve on mass first.

They've been doing it in waves since climate change started to bite in the 80s.