Should not be too hard. Mostly Africa still has a lot of catching up to do in terms of modern farming practices. They could easily make huge improvements simply by doing what the rest of the world has done for decades. And that's before you consider sustainable practices that are currently revolutionizing agriculture which improve productivity by using resources like water and nutrients more optimally which is of course super relevant in places where these things are scarce.

African economies are growing rapidly and as a result they are getting a lot smarter about how they use their resources. Also, there are a lot of African entrepreneurs getting into farming.

Yes, if you develop it.Angola, Zambia, Tanzania , Uganda, Kenia has more than enough water and arable land to accomplish this. But the development part is a big if.

How much of that land would require them to increasingly displace the megafauna?

If they can't then they won't triple their population.

I suspect they can, Africa is urbanising quite quickly at the moment. I'm sure you will see improvements in food production.

The real question is will climate change overwhelm any gains they make.

Do they need to? If they make enough money they can just buy the food they need - and more stuff besides.

Net food exporters are typically countries with a lot of arable land or with relatively low populations. This includes the US, Canada, Argentina, Brazil, Australia, New Zealand, Ukraine, and a few others.

However, they have a lot of existing customers in Europe and Asia who appear to have better prospects for generating foreign exchange to buy food than does Africa. Africa generates foreign exchange mainly by selling raw materials, such as metals, petroleum, etc. Labor, per se, appears to have declining value as population increases and as AI automates more and more work. The incremental value of another billion workers is very low.

But that food has to come from somewhere, and the scale at which we do farming currently is already taking its toll on the environment.

If the scale at which we do farming is taking its toll on the environment at our level of productivity and knowledge, I can only imagine that less productive and less knowledgeable countries will have a much larger negative impact on the environment.

The countries they would buy food from are probably in a much better position to mitigate the harmful effects of industrialized farming. The question is whether this can be done at a price point that is affordable for Africa.

no.

why?

It's a continent with very fragile states arranged around colonial boundaries that make no sense in a post-colonial order, without enough water resources to actually sustain their projected population growth. Carrying capacity is a real thing, and the global population is already almost 8 billion people.

Climate change is going to wreck food supply chains across the globe, since the current food production and distribution has much less excess capacity than it did before.