High environmental costs if 2050 world population be fed

... Well, it depends how, as always.
Below, an excerpt from Bloomberg BusinessWeek's report:

“Current growth in global crop yields will be insufficient to feed the world in 2050,” according to the University of Minnesota. 

 But, if we are nice to each other, we may make it:

More efficient use of arable lands and increasing yield growth rates by sharing best-management practices may help lift production, the study authors wrote. Changing to more plant-based diets and reducing food waste could reduce the large expected growth in demand, according to the researchers. 

With the BAU, Business As Usual, it may not look so good:

Environmental Costs

“A portion of the production shortfall could also be met by expanding croplands, but at a high environmental cost to biodiversity and carbon emissions,” the authors said. 

Source: link.