Population growth - impact on environment and safety

A report says that by the year 2050, our planet will have 9 billion people from 7 billion this year. As many experts says, increase in population will put pressure on scarce resources, environment damage, unemployment and so on. The report says that income will increase and this could lead to more consumption and stresses on finding better methods to produce as at present 7-8 pounds of grains are required for 1 pound of meat and 3-4 pounds for 1 pound cheese or eggs. This may be an indication to have vegetarian food instead of meat products but I do not know whether a person's needs are matched with equal quantity of either grains or meat.