The author means that Alcatraz Island does not have the minimum resources for the native population to live to the full, which will force the natives to submit to white citizens and be exploited as the white man deems necessary.
Explanation:
The standards of the white man reaffirmed his own supremacy over other races, in addition to establishing that these other races should submit to the will of the white man and be exploited so that whites can achieve their goals. For this reason, the author of the text to which the question is referring states that "Alcatraz Island is more suitable for an indigenous reserve," because that island does not have the minimum resources for the indigenous population to be able to live with the basics of comfort. For this reason, to survive, the indigenous population would be forced to submit to the wishes of the white man.
The author is saying that Alcatraz Island would make a good Indian reserve because it is away from the mainland and can give Indians the privacy they deserve and need
