Paul Ralph Ehrlich (born 1932) is an American biologist (specializing in butterflies) at Stanford University, who is a prominent ecologist and demographer.
It is popular to discount Ehrlich, and particularly this book (which begins with the stark prediction that "In the 1970's the world will undergo famines---hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now"). It should be noted that he has substantially revised his predictions in later books such as
The Population Explosion,
Betrayal of Science and Reason: How Anti-Environmental Rhetoric Threatens Our Future, etc.
(It should also be noted that he admittedly lost his 1980 bet with conservative economist Julian Simon, about the trend of prices for certain metals.)
To be sure, his tone in this book was unduly "alarmist"; and his proposal to create a "stable optimum population size for the United States" (Pg. 135) certainly didn't anticipate the dramatic "Green Revolution" increases in agricultural production that would happen in the 1970s and later. His recommendation for "Proselytizing Friends and Associates" (e.g., praising childless people for their "selfless devotion to mankind" on pg. 185; telling families with two children that "two is plenty") seems almost ludicrous, in light of decreasing birth rates, later marriage dates, etc. His appeal to a variant of Pascal's Wager in the last chapter ("In other words, play it safe. If I'm right, we will save the world. If I'm wrong, people will still be better fed...") likely leaves us shaking our heads.
However, a "reality check" is in order. People ARE starving in the world---the Sub-Saharan African countries, India, etc.---and population control is definitely a part of the solution in such areas.
Ehrlich's book is still worth a read to gain "perspective"---but his later books are more useful, and they need to be balanced by also reading people like Julian Simon.