The 1,400 hectares are now Europe's largest "rewilding" project.
And those 40 hectares are currently the most profitable.
Some 20m hectares are estimated to have been deserted; only 12m are under cultivation.
Only 500 hectares are left.We drive on through the majestic Andean canyon.
Today its 41 acres (16.6 hectares) are enclosed, but the old name has been retained.
They show that, every year, a quarter of a million hectares are lost in the Paraguayan Chaco alone.
"Several hundred thousand hectares are now under 'exclosures' - degraded areas in which no cutting and grazing is permitted.
The park covers 10,100 hectares, of which 4,110 hectares are water - either lake or stream.
In the nineteen-seventies, thirty-two hundred hectares of land were flood-prone; today, only forty-nine hectares are.
Brown said the images were evidence that 90% of the 74,000 hectares are "pristine, magnificent forests".
Ranches (estancias), some larger than 25,000 acres (10,000 hectares), are still common in the pastoral region.
