: If it is true, I am prepared to argue that levelling the rain forests for beef production is more valuable than keeping them for some other purpose.
Depends on what the 'other purpose' is. The megaflora produce a significant chunk of the world's oxygen, as well as acting as stabilisers on world and local climate. Without the megafloras' effect on climate, the atmospheric warming caused by industrial society is greatly accelerated; in addition, tropical forests serve as 'carbon sinks' - they absorb carbon dioxide and thus keep the most common greenhouse gas out of the atmosphere.
For example, the Indonesian peat bogs and rainforests in Kalimantan contain enough stored carbon to increase the level of atmospheric carbon dioxide by an estimated 16%; putting this carbon back into the atmosphere causes an accelerated rate of global warming and thus increases the repair bill caused by extreme weather events like the flooding of Mozambique and Hurricane Mitch.
As such, the benefit of making a quick buck in the short term can be outweighed by the cost of cleaning up the consequences.
In addition, a comparatively small amount of people benefit from cattle ranching; but nearly everyone suffers either directly or indirectly from the environmental cost of such activities; floods and mudslides don't limit themselves to hitting cattle ranchers.
The benefits are private; but the costs are public.
Part of the problem lies in the idea that humans can ever 'own' land; the whole idea that parts of the Earth can be 'private property' is fundamentally unsound; as you can't really assign any meaningful criteria of 'ownership' to a tract of land.