The OPs argument would only make sense if importing of food or the massive global logistical system didn't already exist...

If one country stops producing a certain food type, that just increases the amount of money to be made in another country. It will balance itself out pretty quickly, which is why any shortage is acute and not a long term problem.

It's a net gain for the world, especially as they are already growing cannabis in other countries and you're taking money from cartels and criminals and turning it into a self-sustainable crop for impoverished African countries. Ones that provide a superior return than prior ones.

Food is pretty localised for those without good storage means, if the local food supply reduces then prices rise. If there's less food than there was before, and people want the same amount then prices will inflate and overtake the extra income. Those not growing cash crop will fall behind, leading to pressure to stop growing food ... the local community needs food growing but the market won't price it properly. Whilst food is most vital the other crop can be sold in wealthier countries.

People grow coffee and chocolate whilst their countries suffer famines. People sell water rights to multinationals whilst their countries suffer droughts ...

Especially one with a direct side effect of increasing the person's appetite.